--.'~~----'--.. -...•. -., .'."'. . .. '. ....• "'-'-' ,._- .' .~. -.- - ... -_. ~ - ~.., ___ ....... ~ - __ _ """".0, ".-" SA Conference Publication 2067 fj~. "\' /~ ...,9, \- .....'0 ...... -$")- v- .'" ., \ ..P (NASA-CP-2067) THE ROTARY COMBOSTION ENGINE: A CANDIDATE FOR GENERAL AVIATION (N A SA) 1 90 P He A 0 9/ ME A 0 1 esc L 2 1 .Ii N79-15961 THRU N79-15968 Unclas G3/07 43368 The Rotary Combustion Engine ~~Candidate for General Aviation A symposium held at Lewis Research Center Cleveland, Ohio February 28, 1978 NI\S/\ https://ntrs.nasa.gov/search.jsp?R=19790007790 2020-03-22T01:29:38+00:00Z Page intentionally left blank H FOREWORD NASA is engaged in a program to evaluate the potential of several alternative engines for use as general aviation powerplants. The rotary engine is one of the potential candidates. It is of interest because of its relatively low weight, simplicity, compactness, low vibration, low octane fuel requirement, and possible multifuel capability. A l-day symposium on rotary engines was held at the NASA Lewis Research Center, Cleveland, Ohio, to provide those interested with an update on the state of development of these engines as potential powerplants in both aircraft and automobiles. This proceedings of the symposium includes the seven papers presented at the symposium. The symposium was coordinated by Phillip R. Meng of the Lewis Research Center. Edward A. Willis NASA LelO/i s Research Cei1ter Chai rman Robert Brooks Audi NSU Auto Union Cocha'j rman iii CONTENTS FOREWORD • . • • . . • . • • . . • . • • • OVERVIEW OF NASA GENERAL AVIATION PROGRAM Roger L. Winblade, NASA Headquarters .. GENERAL AVIATION ENERGY-CONSERVATION RESEARCH PROGRAMS AT NASA LEWIS RESEARCH CENTER Page . iii 1 Edward A. Wi 11 is, NASA Lewi s Research Center . . . . . . . . . . 13 DEVELOPMENT STATUS OF ROTARY ENGINE AT "fOVO KOGYO Kenichi Yamamoto, Toyo Kogyo Company, Ltd. . . . . . . . . . . . 37 UPDATE OF DEVELOPMENT ON THE NEW AUDI NSU ROTARY ENGINE GENERATION Richard van .Basshuysen, Audi NSU Auto Uni on. . . . . . . . . . . 85 REVIEW OF THE RHEIN-FLUGZEUGBAU WANKEL POWERED AIRCRAFT PROGRAM Manfred Riethmul1er, Audi NSU Auto Union. . . . . . . . • 109 ROTARY ENGINE DEVELOPMENTS AT CURTISS-WRIGHT OVER THE PAST 20 YEARS AND REVIEW OF GENERAL AVIATION ENGINE POTENTIAL Charles Jones, Curtiss-Wright Corporation ....... . ENGINE REQUIREMENTS FOR FUTURE GENERAL AVIATION AIRCRAFT 123 Joseph W. Stickle, NASA Langley Research Center. . . . 175 ATTENDEES. . . . . . . . • . •. • . . . . . • . . . . . . . 187 v OVERVIEW OF NASA GENERAL AVIATION PROGRAM Roger L W'j nb 1 ade NASA Headquarters During the past five years, the NASA efforts devoted to new technology for general aviation have grown steadily~ As described in previous statements, and as illustrated in Figure 1, our efforts have been focused in three area.s: (1) improved safety through improved crashworthy structural design, spin resistance, and improved operations arou.nd uncontrolled airports; (2) redul:!e:d environmental impact for both reciprocating and turbine engines; and (3) research for improvement in the perform- ance of both aerodynw~ic and system components. Figure 2, illustrates a few of the 14 production and prototype aircraft developed by industry that employ ne\'l technology generated by this program. h"hile our current and past effor·ts have been productive in terms of providing new technology for,improved capability in general aviation aircraft, the critical needs of the future will require a shift of emphasis as illustrated by Figure 3. While no abrupt change is envisioned, much of the current activity shown on the left will, over the next several years, become more directly aimed at technology for increased utility and energy efficienoy while w~intaining a significant emphasis OIl improved safety. The R&T program planned for Fiscal Year 1979, while comprised to a large extent of continuing activities, does contain ,some elements rela·ting to the new areas of emphasis. Continuing programs in technology for improved safety are illustrated in Figure 4. The principal effor~ devoted to tm::::ontrolled airport traffic involve' the demonstration of an automatic pilot advisory system to provide pilots near nontower-e~~ipped airports with up-to-date airport and traffic informa't:ion. Since our heari~gs last September, \'16 have been working with the FAA to develop a formal interagency agreement. on a cooperative progranl that insures compatibility of this concept with the automated terminal service project underway in the FAA. By the end of FY 1978, both concepts will be in opera- tional demons'tril:tion and evaluation status. At that point, data from the evaluations will be used by the FAl~ to identify the most effective system concepts as a function of airport activity. In FY 1979 and beyond~ NASA efforts in the evaluation will be in direct support of the PAl"\. I '])/ Improved crashworthiness through new structural design techniques is the objective of a continuing joint effort with the FAA. In FY 1979, the series of impact tests with standard general aviation aircraft will be com- pleted by conducting a limited number of tests with a velocity augmentation system utilizing small rockets to increase the impact velocity up to 90 miles per hour (mph)--30 mph over the maximum free-fall speed. This rocket system was evaluated in a recent test at 75 mph. The higher velocity tests will duplicate some of the impact angles in earlier lower velocity tests to provide comparative data on the effects of higher speeds. In addition, two energy-absorbing seats will be tested in the full-scale impact tests. These seats are being evaluated in sled tests at the FAA Civil Air Aeromedical Institute (CAMI) in Oklahoma City in FY 1978. The FY 1979 tests of the two seat concepts will verify their performance and their suitability for application by the general aviation industry. In another important area, structural concepts capable of substantially increasing the energy-absorbing capability of a fuselage will be fabricated and components will be impact tested during FY 1979. A significant increase in the efforts devoted to· improved stall/spin characteristics was implemented in FY 1978 and will continue· in FY 1979. The augmented efforts have a considerably broader scope than was possible in the past and are now addressing three addi- tional critical factors. Determination of aerodynamic characteristics at high angles of attack, stall/spin-prevention concepts and the development of criteria for emergency spin recovery systems are areas of research now being pursued in addition to the previous efforts in developing test t~chniques, defining normal spin recovery design criteria and consulting with the industry on specific problems. Following theFY 1978 flight evalua.tion of a modified high-wing aircraft, the FY 1979 pr.ogram will include a T-tail configuration and begin the study of .light twin-engined aircraft. As illustrated in Figure 5, ongoing efforts in the development of more efficient aerodynamic components, such as airfoils and high lift devices, will continue in FY 1979. The concentration on drag reduction techniques is intended to provide a generalized design procedure that will reduce the need for the current cut-and-try flight test approach to drag clean-up. In addition, 2 results of ongoing work in the Conventional-takeoff-and- landing (CTOL) area to develop low drag coatings for aerodynamic slrrfaces will be examined for applicability to light aircraft~ Benefits from a particular aerodynamic improve~ent, such as a high-lift airfoil or reduced drag through the use of winglets, will not necessarily be achieved when integrated into an aircraft as a modification. Begin- ning in FY 1978, and continuing, is an effort to provide 9~idclines for optirrillill integration of new aerodynaIllc capabilities into current configurations. A similar effort will explore potential efficiency improvements from new or novel configurations. Illustrated i~ Figure 6, are several areas ~~at are being investigated in an effort to provide greater propulsive efficiency. Turbine engines; both fan and shaft versions, appear to be gaining acceptance across a wider spectrum of aircraft types. Less maintenance, lower cost of turbine fuel, broader tolerance to fuels, and high combustion efficiency make these engine~ potentially viable alternatives to reciprocating engines in the above-400-horsepower class. The Quiet, Clean, General Aviation Turbofan (QCGAT) engine will be completed in FY 1979. Following the evaluation tests by the two contractors, the engines will be delivered to NASA. Subsequent efforts beyond FY 1979 will concentrate on in-house verification testing and performance evaluation at the Lewis Research Center. Existing turbine engines are too large for application to all but the largest general aviation aircraft. In FY 1978, four contractors have undertaken preliminary definition studies of small, 400-horsepower, 800-pound- thrust turbine engines. In FY 1979, detailed definition studies will be initiated including a careful evaluation of the airframe requirements to properly incorporate such an engine into the aircraft. Significant losses are encountered during the installation of reciprocating engines. Drag generated by cooling requirements, cowling drag and adverse interactions between the propeller and the nacelle are estimated to be from 5 to 20 percent of the cruise drag of current aircraft. Ongoing stud£es in each of these areas will provide design procedures and data for optimizing engine installations. 3 Closely coupled to these tasks are the efforts in propeller optimization. During FY 1979, design and fabrication of model hardware for propeller/nacelle flow field investigations will be underway, as will research on advanced blade sectio~s. More basic studies of fuel tolerance and cycle effi- ~iency, including evaluation of diesel and rotary engines, will continue during FY 1979. As illustrated in Figure 7, the utility of light aircraft asa moce of transportation is heavily dependent upon the ability to operate in adverse weather and a complex air traffic system. wnile accomplished routinely by the airlines, the differences in airborne equipment, operational requirements; ground facilities and flight crew make general aviation instrument operations considerably more challenging. ContinuL"1g research on advanced integrated avionics, studi~s of advanced navigation concepts and previous work on stability, control and handling qualities for general aviation represent a technology base that is available for improving the safety and reliability of instrument flight. Information available to us through the Aviation Safety Reporting System (ASRS) and other sources indicates a number of problems exist with single-pilot instr~~ent flight-rule (IFR) operations. During FY 1979, we will be initiating efforts to isolate the most critical prob- lems so.that we may begin, in consultation with users and FAA, to explore concepts for resolving them. Our approach will be to establish realistic operating scenarios and, through simulation, identify the operating and procedural conditions adversely aff~cting the single pilot's flying task. Although premature to speak about specific areas we would investigate to resolve problems, we envision that we may be looking into such ,matters as charting, trai!ling requirements, and air traffic control (ATC) procedures. In addition to the work outlined here, we also will be defining plans for examining single-pilot IFR issues withi~ L~e context of the cockpit-displayed traffic information program des- cribed earlier in ~~e testimony. A symposium on Short-Haul, Small Corrununi ty Air Service was held at the Ames Research Center in early FY 1978. Participants represented all facets of the industry providing small community air service, inc~uding researchers, regulators, manufacturer~ and operators. 4 " In general, the purpose was to identify what, if any, technologies should be developed to enhance this very vital segment of civil air transportationo Current airline service and future prospects were examined as were the results of past studies. Aircraft design and operating system requirements were reviewed in terms of technology opportunities and some related NASA research programs. Conclusions resulting from these deliberations were t..~at there is a lack of an appropriate sized and performing modern aircraft available to the commuter market and that, in general, shrinking of current transport technology much below 50-60 passengers would not be economically viable. As illustrated in Figure 8, a study was initiated in FY 1978 to explore what, if any, technology limits exist that preclude the general aviation industry's development of a larger aircraft matched to the commuter airline requirements. FY 1979 activities will continue these studies, concentrating on definition of the appropriate NASA role. in resolving any problems identified in the current study. The utility and productivity of aircraft dedicated to the performance of a special mission can be enhCinced if the aircraft is specifically tailored to the require- ments of the task. Such is the situation 'tIith aircraft used to apply agricultural materials. Since the primary transport mechanism for the materials, once ejected from the aircraft, is wake ge71erated by the aircraft, the width of the pattern and its evenness are directly inf luenced by the uniformity of t.~e dOWTI\Olash. As illustrated in Figure 9, the wake of the aircraft and the propeller slipstream seriously detract from t.."1e ability to apply a uniform layer of material. Relying on facilities and techniques develcped in the study of trailing vortices, model tests anc analytical studies will be carried out to define acce'Ctable mod- ifications to current aircraft that will {·,'Drove the uniformi ty of the pa tt.ern by tailoring the ;/a}:e characteristics. ~ffiile a relatively low-level effort, it does capitalize on a unique area of expertise within NASA and does hold the promise of significant return if successful.~ In summary the general aviation research ana technology program planned for FY 1979 is well balanced and is 5 addressing the most critical problems identified as future limits to growth. This shift in. emphasis away from the near-term pr:oblems to a next generation timeframe in aerodynamics, propulsion and avionics is compatible with the time required for the eyaluation and incorpo- ration of .new technology by ~~e ~ndustry. 6 CURRENT TECHNOLOGY EFFORTS SAFETY AIRFOIL DEVELO'MUNT IMI'OATANCE CI ~ ; • z ~ ~ ~ ~ u LOW MEDIUM HIGH SPEED SPEED SPEED AERODYNAMIC AND SYSTEM IMPROVEMENTS ENVIRONMENTAL IMPACT Fig ure 1 APPLICATION OF NASA RESEARCH Figure 2 7 TECHNOL . GY PROGRAM EMPHASIS CURRENT R&T EMPHASIS AERO DYNAMIC AND SYSTEM PeRFOR MANCE ENVIROMENTAL IMPACT SAFETY 1980 TIME Figure 3 SAFETY 1990 FUTURE R&T NEEDS INCREASED UTILITY EN ERGY EFFICIENCY SAFETY OPERATIONS & PROCEDURES CRASHWORTHIN ESS STA Ll/SPIN RESEARCH Figure 4 8 ENERGY EFFICIENCY AERODYNAMICS HIGH LIFT DEVICES DRAG REDUCTION OPTIMIZED DESIGN PROPEI.LER PERFORMANCE f ( \ / COOUN (l DRAG CYCLE , I _ . NEW CONFIGURATION Figu re 5 PROPULSION EFFICIENCY r t' r • \1 J • J.... C1 ., I d (; I' 10 o. .L ,l? or Hd 1" • TECHNOLOGY FOR REDUCED FUEL CONSUMPTION OPTIMIZATION CYC LE EFFICIENCY Figu re (1 9 SINGLE ILOT INSTRUMENT FLIGHT Figure 7 COMMUTER/AIR TAXI VEHICLE TECHNOLOGY IMPROVED SMAll COMMUNITY AIR SERVICE GENERAL AVIATION TECHNOLOGY \( SIZE \ PERFORMANCE \ COST \ Figure 8 10 TRANSPORT TECHNOLOGY AGRICULTURAL AVIATION INCREASED UTILITY THR OUGH IMPROVED FLOW FIELD AIRCRAFT WAKE MODIFICATION WITH WINGTIP SPLINES Figure 9 ( • "_1 I· r. ~ 0 .... -- '0J1. QUAl. l'l' 11 GENERAL AVIATION ENERGY-CONSERVATION RESEARCH PROGRAMS AT NASA LEWIS RESEARCH CENTER ~dward A. Willis NASA Lewis Research Center SUI1l-1ARY A review is presented of non-turhine general aviation engine pro- "rams underway at the NASA-Lewis Research Center in Cleveland, Ohio. The f11'oqr("!:1 encompasses conventional, lightweiqht diesel and rotary engines. Its three major thrusts are, in order of priority: (a) reduced SFC's; (b) il1:1!'Oved fuels tolerance; and (c) reducing emissions. Current and plan~ad future programs "in such areas as lean operation, improved fuel mananement, advanced cooling techniques and advanced engine concepts, are described. These are expected to lay the technology base, by the mid to latter 1980's, for engines whose total fuel costs are as much as 30% lower than today's conventional engines. HlTRODUCTIOIl Gen~ral aviation fuel costs have nearly doubled since 1973 and the industry has been plagued by intermittent shortages of specialized fuel qrades. The oil companies statements at this Conference, for instance, indicate that avgas may rise to $1.50 per gallon or more by 1982. This situation is believed likely to continue and become progressively worse in the forseeable future. It is particularly a problem for the piston-engine segment of the general aviation fleet, because these engines reflect a \LvJ. II level of technology .. and require very specific ~)rades of gasoline. The industry apparently lacks the independent financial and technological means in such areas as advanced combustion and cooling research, to significantly enlarge the fuel tolerance of either current or next-generation engines. Al- though theIV2()0,000 general aviation airplanes supply essential transportation services to about 13,200 airports (compared to 425 served by commercial air- lines), avgas represents only about 0.3% of the total transportation fuels market. This may be too small to significantly constrain the refiners' future product split decisions. Government pressures toward the most energy-efficient product split from available crudes and other raw materials, may well have a greater i~pact on these decisions. It is therefore appropriate that Govern- ment technology be applied to help solve the resulting problems. At Lewis, the General Aviation Branch was formally established earlier this year, following -several years of initial facility and instru- mentation development and preliminary efforts aimed at emissions reduction. More recently, in view of the EPA's apparent intent to withdraw the emissions standards, the emphasis of the program has shifted toward fuel conservation and multifuel and/or broad specification fuels capability. Figure 1 illustrates our relation to other general aviation programs within the Lewis organization. In broad terms, our aim is to enable light planes to b~rn as little as possible of the cheapest fuels available. More specifically, our long- term (1985) objective is to lay the technology base for an efficient, reason- ably priced multifuel or alternative fuel engine whose fuel costs (based on 1977 dollars and prices) could be as much as 30% less than present day engines. Because of product longevity and comparatively low annual production rates, the benefits of a next-generation multifuel engine, although valuable to the individual owner or operator, would require a period of years to significant1y upgrade the overall fleet. Hence the program necessarily also includes con- sideration of applicable technology for current-production type engines. We would prefer, however, to leave any detailed discussion of near-term develop- ments ta the respective engine companies. This discussion will therefore address the longer-term prospects, including a couple of often-overlooked and much-neglected concepts -- the rotary and the lightweight diesel -- that we now see as having considerable promise in the 1985-1990 era. PROGRAt1 TO DATE Several Lewis accomplishments to date deserve mention. Three sophis- ticated engine test cells have been built from scratch, with one more in progress. Figure 2 indicates the capabilities and leading features of the currently-operational cells. Figure 3(a) is a view inside the aircraft engine test cell, with the engine (a TSIO-360) in the foreground. The cooling-air hood has been removed for clarity a.nd the electric motoring dynamometer may be seen at the left. The associated control room is shown in Figure 3(b). These highly automated cells feature real-time data readout via microprocessor tech- nology, and we believe that they compare favorably with any of their kind in the world. An example of our on-line data readout is given in Figure 4, which illustrates in bar-chart format, the IMEP measured for 100 successive cycles of one cylinder on the Chevrolet enqine. The two samples shown, b~th for the same speed and load, illustrate what can happen when the engine is excessively leaned out. At left, the mixture strength was about stoichiometric and there was little variation behJeen the IMEP's of successive cycles. The engine was then leaned out, but not to the point where the operator could detect visual or audible signs of rough running. Nevertheless, many slow burns and one outright misfire (the small negative bar) can be seen. This results in increased HC emissions and SFC. The high IMEP's seen in other cycles is indicative of high peak pressure and possibly detonation. With the aid of such real-time data capabilities, the test engineer can make sure to get good data the first time, every time. Lengthy delays for data reduction are largely eliminated. If properly utilized, the automated test cell can be an order of magnitude more productive than a conventional cell. 14 Using these in-house facilities and other Lewis resources, together with a continuing series of industry contracts, we have completed substantial programs in such areas as: basic engine characterization (Ref. 1); effect of temperature, humidity and lean operation on fuel economy, emissions and cooling requirements (Ref. 2); hydrogen enrichment of fuel (Ref. 3); and theQretical analyses of cooling fins (Ref. 4). Also, progress has been made toward the development of advanced analytical tools such as an Otto Cycle performance and emissions prediction computer code (Ref. 5). The results from these plus the contract programs are such that we expect to demonstrate, by the end of 1979, the technolo~y base to approach or meet the former emissions standards. This is not a moot accomplishment, since reducing emissions is clearly desirable even if no longer mandatory. Also, most of the programs led to be fuel-conservative accomplishments as well. For example, lar~e amounts of scatter observed in prior emissions data prompted us to include the effects of atmospheric temperature and humidity in our own program. Typical results obtained in the aircraft engine test cell with conventional mixture control are shown in Figure 5(a). The He emissions level is plotted vs. temperature for relative humidities of 0 and 80%. The level increased by a factor of about 4 between "cool, dry" and "hots humid" con- ditions. The fuel/air ratio increased by about 20% at the same time due to the decreased air density and displacement of air by water vapor. Since the engine was run at constant speed/load conditions, fuel consumption suffered by the same amount. A second series of tests, illustrated in Figure 5(b) was run to evaluate the situation when the fuel/air ratio was held constant at the "cool, dry" value of 0.093. The result, as shown by the solid curve between the two shaded regions (representing 80% humidity) was a much smaller increase in HC emissions. Since fuel/ai:r was held constant, there was no penalty in fuel consumption. The upper curve represents the 80% humidity case previously shown, \'lhere the conventional mixture control allowed fuel/air to vary. The shaded area between the two curves shows that most of the initially observed increase in Hr was due to the induced change in fuel/air. The lower shaded area illustrates the smaller increase due to changes in temperature and humidity alone. From these results, it is clear that an automatic mixture control d \\ \\ \\ system, capable of holding a desired fuel/air ratio despite atmospheric variations, is needed to improve both fuel economy and emissions. The hydrogen injection program is another case in point. Both in our own programs (Ref. 3) and a parallel JPL effort (Ref. 6) it was initially thought that the free hydrogen, by permitting leaner operation, would improve both economy and emissions. A considerable amount of extra spark advance was required to support lean operation, whether hydrogen was used or not. The results are illustrated in Figure 6, where SFC is plotted vs. mixture strength at typical load conditions for an automotive engine (NASA) and an aircraft engine (JPL). Operation with gasoline only is represented by the solid curves while the dashed curves denote gasoline plus the indicated amounts of hydrogen. In each case the spark advance was maintained at an optimum or near-optimum setting. typically 300 - 350 BTDC for the aircraft engine and over 400 for the auto engine. Under these conditions, the minimum SFC buckets occurred w'ith gasoline only even though the auto engine's lean limit was noticeably extended 15 by using hydrogen. The amount of extra spark advance required ,to obtain these results is incompatible with starting and high-power op~ration. Thus, a variable timing ignition system is desirable and perhaps ~n essential ingredient in realizing the indicated improvement of 5 or 10% SFC below the normal stoichiometric or slightly rich condition in the ~ircraft engine. ONGOING AND FUTURE PROGRAMS With this basic work behind us, the current program (Fig. 7) in- cludes elements designed to achieve a technology base which will enable general aviatior to live with the fuels of the future. As indicated, the program includes near-term elements which could improve the fuel economy of present-day type engines, as well as longer-term elements leading to broad-specification or true multi-fuel capability (together with further reductions in SFC). While recognizing the inherent multi-fuel capability of other candidates such as gas turbine or Stirling engines, the program discussed here is now oriented to\'/aY'd diesel and rotary combustion engines in addition to advanced piston engines~ All of these can benefit immediately from the results of ongoing automotive diesel and stratified charge research programs and offer significant benefits without having to wait for "technology breakthroughs" in one or more areas. We are of course, monitoring ongoing turbine and automotive Stirling programs for applicable developments. Advanced Piston Engines Current production general aviation piston engines reflect a level of technology that existed at the end of W. W. II. It seems reasonable to expect that they could be improved substantially by incorporating applicable developments of the last 30 years. In particular, the automotive research programs that have been mounted within the past decade, would appear to be a rich source of new technology for general aviation. While the most in- teresting developments are proprietary and cannot be discussed at this time, it is to be hoped that arrangements beneficial to genera1 aviation can be worked out among the companies concerned. For conventional engines, the lean out approach should yield about a 10% improvement in basic engine SFC levels. To realize this benefit, we have initiated programs in: (1) improved fuel injection; (2) variable timing ignition systems; and (3) improved cooling. . Improved fuel injection together with even air distribution is needed to minimize the cy1'inder-to-cylinder variations of fuel/air ratio. ~1ore leaning can then be accomplished, since the lean limit for the engine as a whole is set by the leanest cylinder. Variable timing ignition systems are required, because as sho\'m by our own and JPL testing, radical spark advance is required to extend the lean limit and obtain very low SFC's on some engines. The degree of advanc!e required is incompatible with starting and high power requirements. 16 In many turbocharged installations, the amount of leaning made possible by the two items above would be accompanied by excessive CHT's and detonation. This wO,uld negate the potential SFC improvement due to leaning unless better coolirlg is provided. Potential improvements are forseen in several areas. Exhaust port liners and/or thermal barrier coatings will decrease the heat load into the cylinder head by as much as 35%. Advanced designed cooling fins and passages can more effectively dissipate the remainder of the heat load. The resulting lower CHT's and elimination of hot spots will enable the engine to run leaner and/or at a higher compression ratio without detonating. For turbocharged engines, a 5 to 10% reduction in SFC is anticipated from these improvements. Alternatively, the lower CHT's could enable the engine to burn lower octane fuel. Figure 8 illustrates a hypothetical cylinder head design that incorporates the port liners, improved fuel injection and other advance- ments into a well-integrated package. f10re efficient inlets, baffles~ fins and exits can reduce the cooling air pressure drop for a given heat load by a factor of 2 or more. The resulting decrease in cooling drag is equivalent to a further fuel economy improvement of up to 5%. This is additive to the above and also applies to those engines that are already capable of operating lean. In the longer term, advanced combustion research is essential to utilize cheaper, more readily available fuels. It should be noted that, based on current fuel prices, 100 octane avgas is 10 to 15% more expensive per gallon than diesel or Jet-A fuels. These fuels however, contain about 10% more BTU's per gallon than avgas because of their greater density. Thus a fuel cost saving potential of 20% or more is readily apparent, even if SFC's are not im- proved at all. Automotive research results indicate that novel combustion geometries coupled with vapor-phase fuel injection, may significantly broaden the fuel tolerance of an otherwise conventional engine. Diesel Engines Diesel engines are of interest because of their well-known potential for low SFC. They can also burn kerosine-type jet fuels with little difficulty. These types of fuel are generally cheaper than avgas. Since the diesel is not detonation-limited, it can run at high compression ratios and/or can be turbocharged to exceptionally high power densities. The problem with diesels is weight. A normally aspirated diesel suffers an -immediate specific power penalt.y of about 15% compared to a gasoline engine because only al)nut 85% of the theoretically-available air per cycle can be burned efficiently. At typically high diesel compression ratios, the high peak firing pressures result in major structural weight p~nalties in addition. Based on these considerations, it was felt that a low compression, turbocharged diesel concept might offer the best trade-o;f between W7i ght and performance. 17 Initial efforts, however, showed that it is no simple matter to obtain good diesel combustion at low compression ratios. Tests at the U. of ~1ichigan (Ref. 7) of a dieselized aircraft cylinder mounted on a single-cylinder crank-case showed unexpectedly high SFC due to poor com- bustion (Fig. 10). The problems are ultimately due to the major geometrical differences between an aircraft gasoline engine's combustion chamber and the typical diesel's. The former has low turbulence and a high surface-to-volume ratio to promote cooling. The latter normally would be a high turbulence design with a compact combustion volume intended to keep the heat in. The work however is being continued to optimize the combustion chamber geometry and we expect to reach the indicated BSFC level of about 0.42 after another years' effort. Figure 10 illustrates a turbocharged diesel concept in which an aux- iliary combustor fed by compressor air is used to provide additional power to the turbine. In this concept the power output is limited only by cooling and structural consideration. The turbomachinery can be started and run independently of the diesel cylinders to provide hot compressed air for starting aryd low power operation. This concept has been under study and development for some time by the Hyperbar Diesel Co. in France. The French results (Ref. 8) indicated that SFC's at least as low as 0.38 can be obtained at cruise to rated power conditions. At Lewis, we are in'itiating a research program on this concept, using a single-cylinder research engine, with which we hope to further improve this figure. Our diesel test cell (Figure 11) is presently being checked out, is scheduled for start up in December 1977 and should be operating productively by early 1978. Rotary Eng; nes The rotary or Wankel engine (Figure 12) ;s of great interest because of its established advantages of simplicity, light weight, compactness, clean low-drag installation features, low vibration and reduced cabin noise. Its reputed disadvantages of high fuel consumption and emissions, have been largely over- come by continued research, some in this country and some by foreign automotive companies. For example, according to EPA "city cycle" driving test results, the 1973 t1azda gave 10.6 mpg while the 1977 version showed nearly a 100% improvement to 20 mpg. The detailed SFC and raw-emissions data are proprietary at this time, but it can be stated that the best of the late-model automotive rotaries are becoming competitive with their piston-powered counterparts. The price situation for rotaries ;s uncertain at this time. The parts are few and simple but require high-grade materials and very close- tolerance machining. On the other hand, the concept clearly lends itself to high-volume automated producibility. Co-production arrangements among foreign companies are being considered (Ref. 9 and 10) to establish a favorable production-volume basis. Unconfirmed reports (Ref. 10) also suggest that General t10tors will re-enter the rotary field in the early 1980's. If this occurs, a volume production basis would be established in this country as well. 18 f , These potential developments are highly significant, because the same toolin~ might also be used to manufacture derivative aircraft engines or key components thereof at reasonable cost. For aircraft applications, two distinct versions of the rotar'Y engine are of interest and they will be separately discussed. A naturally aspirated j spark ignited version appears to be most attractive for lower- power applications and whenever turbocharging would not be desirable. Figure 13 illustrates results obtained last year in testing a Curtiss-Wright RC-2-75 engine under a NASA contract (Ref. 11). It's best SFC of about 0.54 might be good enough for an automotive application, but is not competitive with even a current production normally aspirated aircraft engine. On the other hand, it met the EPA NOx and CO standards, and was only slightly above the He standard. It's specific weight Df about 1.25 lbs/hp is most attractive. It shou,ld be noted that the rotary, because of heat losses from its high surface to volume combustion chambers is less subject to detonation and has a lower octane requirement than a piston engine. Also, it is insensitive to lead in the fuel due to self-cleaning internal surfaces and having no valves to stick. At a given compression ratio, therefore, the rotary is more fuel-tolerant than a piston en~ine. Alternatively, the rotary can run a higher compression ratio on the same fuel. Returning to Figure 13, single rotor tests at an increased compression ratio (to 8.5:1) with other minor changes, showed significantly better SFC's coupled with acceptable HC emissions. The Polish PZL Franklin engines currently run a 9.5:1 compression ratio on 100/130 octane avgas, according to the manufacturers' literature. Based on the above arguments, we would expect that the rotary could run at least that high. On that rationale, we have projected the 8.5:1 rotary test points to 9.5:1 and expect to be at the more competitive level shown in abGut a year. Based on unconfirmed reports concerning the new Toyota rotary (Ref. 10) we anti ci pate that the results shown can be fw'ther improved by employing a comparatively simple, partial charge-stratification scheme. This may also improve the engine's fuel-tolerance and emissions characteristics. Attempts to further improve the rotary's SFC by going to diesel operation have thus far proven discouraging. Considering the effects of heat losses, seal leakage and manufacturing tolerances, it appears impracticable to obtain a high enough compression ratio. On the other hand, much the same result can be obtained via stratified charge operation. As Figure 14 suggests, the principle is that fuel is injected directly into the combustion chamber via a high pressure injector, as in a diesel. But instead of depending on compression heat to ignite the fuel spray, this is accomplished by a separate means such as an arc or a timed high-energy spark. The rotary is uniquely well adaptable to this approach for two reasons. First, the elongated rotarY combustion chamber, in its natural sweeping motion past fixed injection and ignition points yields inherent charge-stratification. No power-robbing pre-chamber is needed; in effect, the combustion volume is moved through a stationary flame front. This keeps fuel out of the rotor trailing-edge region where poor combustion is apparently responsible for part of the rotary's past SFC and He emissions problems. 19 Secondly, the firing impulses of a two rotor Wankel engine are as smooth as those of a 6-cylinder piston engine. Thus, it needs only 1/3 as many high pressure injectors as a comparable diesel or stratified charge piston engine; and hence is much better able to absorb the cost and weight penaities of this sophisticated and typically expensive equipment. The resulting engine would potentially have a true multifuel capability in that it has neither octane nor cetane requirements. Like the diesel, it can be turbocharged to very high pOWer densities. Although presumably designed for optimum performance and efficiency on a fuel of choice -- such as diesel or Jet fuel -- it should have "keep flying" capability on gasoline in case of shortage or unavailability. Operations at a small FBO may be a case in point. Such advantages have not gone unnoticed Oy other investigators. A perusal of fundamental and applied research in the recent literature (Refs. 12 through 14) indicates tha+ the technology is now at hand to develop a multi fuel stratified charge rotary whose SFC, as projected in Figure 15, is at least comparable to that of the best current production aircraft engines. And all the while it is using a cheap i'lnd very available fuel. The results shown are for a natura1'1y aspi rated engine \'Jith a sped fi c weight of about 1.25. Our goal for 1985 is to improve these figures to a specific weiqht of less than 1.0 and a SFC under 0.40. ECOflmnc H1PACT The discussion thus far has only concerned technology, but several other considerations are also most important. They all relate, directly or indirectly, to the issue of cost. It already costs money to maintain the industry's excellent present standards of safety, reliability, etc. Will advanced technology add more to the bill? If so, who pays and where does the money come from? These very legitimate questions cannot be definitively answered now, but neither can they be avoided. Extensive studies will be needed to fully assess the economic impact of advanced technology on general aviation. I disagree however, with the notion that high-technology products are necessarily complicated and expensive; and would like to cite two examples to support my view. The Diesel Rabbit automobile introduced this year is being profitably sold for about $170 more than its gasoline counterpart -- a premium of only 3-4% of the usual retail price range. Without attempting to account for the economic value of diesel durab~lity, this premium will be recovered in fuel cost savings* alone in about 2 years of average driving. Thereafter, this automobile will in effect be making money for its owner. So technology doesn't have to be expensive or unprofitable if it is properly combined with value ----.- . englneenng. * Based on EPA mileage estimates and late 1977 motor fuel retail prices. 20 The second example concerns a hypothetical high-performance general aviation business twin. The Appendix outlines some admittedly crude, SlJccess~ oriented and over-simplified calculations to compare a status-quo engine and an advanced engine in the same airplane. For the one model considered, this provides a preliminary estimate of the annual fuel-cost savings that might be expected from advanced propulsion technology. The numbers representing the baseline airplane and engine are not specific to any current models but are thought to be representative. The maximum cruise SFC is installation dependent and varies with the amount of fuel required to cool the engine; the spread of 0.47 to 0.41 covers most installations. Fuel prices were established for this exercise by extra- polating the late 1977 pricing structure to the levels predicted at this Con- ference for about 1982. On this basis, the annual fuel bill for 600 hours utilization would range from about $35,000 to $30,000. For the advanced engine, presumably a lightweight diesel or stratified- charge rotary, we chose the most ,optimi sti c numbers from the cont.ext of the present discussions: SFC = 0.38 lb/hp-hr; specific weight = 1 lb/hp; and a cooling drag reduction equivalent to 4% of the cruise thrust hp. This results in an annual fuel bill of about $19,600 -- a savings of $12,800 to $15,400 -- if it is assumed that the weight saved in engine and fuel is added to the payload. In this case we achieve a 36-44% fuel cost savings coupled with a 55% increase in payload. Alternatively, if the airplane is simply flown lighter, the engine may be throttled back to cruise at the same speed; the fuel bill is then about $17,700 which represents a savings of nearly 50%. The above results vary linearly with the annual utilization rate of the airplane, as shown in Figure 16. For the nominal 600 hr. rate, the maximum savings of about $17,300 probably represents 5 to 7% of the airplane's base price. Thus, a premium of 10% of the selling price could be recovered in 1~ to 2 years. Thereafter, within its expected lifetime, the airplane would probably repay its original base purchase price in fuel savings alone. The above results assume that the best of the anticipated developments occur simultaneously aRd are in that sense optimistic. On the other hand, no effort has been made here to estimate the possibly significant added benefits that could be expected fro~ re-sizing and otherwise re-optimizing the airplane to better match the new engine. This would be especially important for the rotary engine since it differs in several major respects from current practice No economic credit was estimated for the better durability and reliability anticipated of an advanced diesel or rotary engine. As these same factors also influence safety, the ultimate benefit may be very significant. Con- Sidering these factors, even a 50% savings may be conservative. As mentioned, extensive studies will be necessary to evaluate the economic impact of advanced technology on all types, classes and uses of general aviation.. In the end, the more conservative fuel cost savings of 21 30% mentioned before may prove to be more representative. But even that is enough to eventually amortize half the base price of many general aviation airplanes. This should prove most attractive to owners and manufacturel's al i ke. A sizeable investment will be required, however, to realize this very desirable state of affairs. The Government research programs I described are not cheap and the industry is conducting additional work on its own. When the technology base has been laid, the industry will then have to develop, cert i fy and too 1 up for the' new des i gns. How is a 11 thi s to be pa i d for? An extension of the. preceding business-twin example suggests that the eventual benefit to the economy as a whole could be surprisingly large and of a sufficient order of magnitude to justify a respectable investment. Assume that an annual production of 100 advanced propulsion airplanes is established to upgrade a static, 2000 airplane fleet on a 20-year life cycle. The airplanes, engines and utilization are as described in Appendix A, except that the more conservative 30% annual fuel cost savings is assumed. Each new airplane then would "earn" on the order of $10,000 per year. The first year, 100 upgraded airplanes replace 100 retiring status-quo airplanes and collectively "earn" $ltt The second year, the 200 new airplanes "earnll $2t1. and so forth. By the tenth year, 1000 upgraded airplanes are earning $lor1. This when added to the sum of all prior year savings ($lM + $2M •.• + $9M + $lOM) yields an accumulated total benefit to the economy of $55M, compared to prolonging the status quo. By the end of the 20-year life cycle, the now- upgraded fleet has produced a total benefit of $210M to the economy and the benefit is increasing at the rate of $20M/year. Recall that this is for one airplane model only, which represents less than 1/10 of the total general aviation fleet and a modest fraction of the industry's dollar volume. If all elements of the piston-engine fleet were similarly upgraded, the total benefit after 20 or 25 years may approach the $1 Billion order of magnitude. This would appear to justify a sizeable initial investment. CONCLUDING REMARKS In conclusion, I would like to offer some comments that primarily reflect my own viewpoint rather than matters of policy or settled, opinion within NASA. Regardless of one's vie\'/s on the real nature of the "energy crisis", it does appear that conservation and energy efficiency will be part of " the scene for as far as we can see into the future. What does this mean to general aviation? My personal views on the subject are expressed on the last figure. Sooner or later -- perhaps by the early to middle 80's, some customary grades of fuel may simply become unavailable. Or, they may remain available, but at what price? Clearly, it will be economically desirable to take advantage of the broad-specification, high volume fuels of the future. As indicated, several work areas must be addressed to approach this goal in eithe~ a long-term or short-term sense. It is equally desirable to use less of those fuels, if only to keep from going broke. 22 I have now indicated the main technological steps along the path I think we must follow, although only the longer-term aspects were dis- cussed in this presentation. The ultimate benefits are indicated at the bottom. Our earlier work shows that economy and emissions are interlocked to such an extent that the former EPA standards wil' probably be met anyway, in the due course of events. Not by 1980, but eventually. r~uch work remains to demonstrate that some of the advanced engine's anticipated advantages, in such areas as durability and reliability, are in fact real. Extensive studies will be needed to more accurately evaluate the economic impact of these developments, and it is hoped that all segments of the industry will contribute to these studies. My own highly preliminary assess- ment should be taken as indicating an order-of-magnitude potential only. But the potential appears to be there. If the re5earch programs turn out as expected, the benefits are large enough to be compelling. 23 APPENDIX - SIMPLIFIED ESTIMATE OF ANNUAL FUEL COST SAVINGS DUE TO ADVANCED ENGIHES (ANTICIPATED 1982 FUEL PRICES) Baseline Airplane: Utilization: Baseline Engine: {\dvanced Engine: Annual Saving: In Addition: Alternatively: 6-place pressurized business twin, turbocharged 750 lb payload class, 200+ kt. max. cruise @ 20,000 ft and lId = 8.5 .. 600hrs/year @ max. cruise Rating/weight: 333 hp/500 lbs t~ax. cruise power/SFC: 250 hp*; 0.47 to (0.41) lbs/hp-hr Fuel flow: 235 lbs/hr (2-engines) (205 @ 0.41 SFC) Annual fuel use: 141000 lbs Fuel: 100 octane avgas @ $1.50/gal or 24.8¢/lb Density/heating value: 6.042 lbs/gal; 18600 BTU/lb Annual fuel bill: $34968 ($30504 @ 0.41 SFC) Rating/weight: 333 hp/333 lbs t1ax. cruise powel"/SFC: 240 hp**; 0.38 Fuel flow: 184.2 lbs/hr (2-engines) Annual fuel use: 109440 lbs/year Fuel: Diesel 2 @ $1.35/gal or 17.9¢/lb Density/heating value: 7.544 lb/gal; 18600 BTU/lb Annual fuel bill: $19590 $15378 to $10914 or 36-44%, of which about half is due to direct SFC improvement, plus reduced cooling drag; and the remainder is due to lower fuel price/BTU Payload may be increased by over 400 lbs (55%) due to the lighter engine and the 200 lb. fuel savings recorded over a typical 4-hour mission. The airplane may be flown throttled-back since it is lighter (assuming the lId ratio stays constant at about 8.5). This results in another fuel savings of about 72 lbs. over the same 4-hour mission, and brings the annual fuel cost down to $17667. The savings is then 49.5%. ($12873 and 42% @ 0.41 SFC). * Includes 25 hp loss due to drag of conventional cooling system. ** Includes 15 hp loss due to drag of improved cooling system. 24 , ' i REFERENCES 1. Anon: IIAircraft Piston Engine Exhaust Emissions Symposium, Lewis Research Center, September 14-15, 1976 11 • NASA CP-2005. 2 ••. , t1eng, P. R.; Cosgrove, [I.; Skorobatckyi, M.; and Kempke, L L: "Per- formance alld Emission.s of an AVCO-Lycoming 0-320-0IAO Air-Caoled Light Aircl'aft Enginf!". NASA n1 X-73500, August 1976. .3-. Casgidy, J. F.: "Emissions and Total Energy Consumption of a Multi- cylinder Piston Engine Running on Gasoline and a Hydrogen Gasoline t1i xture". NASA TN 0-8487, ~1ay 1977. 4. Siegel, R. and Graham, R. l~.: "Effect of Finned Passage Length on Optimization of Cylinder Head Cooling Fins". NASA TP-1054, in press. 5. Zeleznik, F. J. and}1cBride, B. J.: "Modeling the Complete Gtto Cycle- Preliminary Version". SAE Paper 770191, March 1977. 6. Chirivella, J. E.: Duke, L. A.; and r·1enard, H. A.: "High Fuel Economy in an Aircraft Piston Engine When Operating Ultralean ll • SAE , . . ' Paper 770488, April 1977. -t.~ Kroeger, R. A.; Bottrell, M. S.; Gaynor, T. L.; and Bachle, C. F.: ilL i ghtwei g,ht Low Cempress; on Aircraft Diesel Engine". Universi ty of Michigan/NASA final report in progress. 8. t1elchior, J. and Andre-Talamon, T.: "Hyperbar System of High Super- charging". SAE Paper 740723, 1974. 9. Anon: "Toyo Kogyo & Audi NSU Discuss Production Sharing". The Japan Economic Journal, November 1~ 1977. 10. Anon: "Toyota Unveils Stratified-Charge Rotary Car It Could Power, Audi, ToyoKogyo Share Wankel Parts, Technology". Gordon Reports & Auto World, Volume XIII, No. 21, November 25, 1977. 11. Berkowitz, t~.; Hermes, W. L.; Mount, R. L; and ~1eyers, D.: "Per- formance, Emissions and Physical Characteristics of a Rotating ~ Combustion Aircraft Engine" , Curtiss-Wright/NASA CR-135119, Dec. 1976. 12. Jones, C.; Lamping, H. D.; Mount, R. L; and Meyers, D. M.: "An Update of the Direct-Injected Stratified Charge Rotary Combustion Engine Develop- ments at Curtiss-Wright". SAE Paper 770044~ 1977. 13. Bracco, F. V.: "Theoretical Analys'is of Stratified, Two-Phase Wankel Engine Combustion", Combustion and Science Technology, Vol. 8, No. 1-2, September/October 1973, pp. 69-84. 14. Reitz, R. D. and Bracco, F. V.: "Studies Toward Optimal Charge Stratification in a Rotary Engine ll , Combustion Science and Technology, Vol. 12~ No. 1-3, Jan. 1976, pp. 63-74. 25 FACILITY SE-17 SE-11 SE-6 ENERGY PROGRAMS DIRECTORATE (G. M. AULTl , _______ 0< ____________________________ _ IRECIPROCATING ENGINES (UP TO I !ROTARY ENGINES 800 SHP)\ f------f .... ------- ---------------______ : AERONAUTICS DIRECTORATE CW. L STEWART) GENERAL AVIATION BRANCH COMMERCIAL TURBOFANS, TURBOPROPS QCGAT-LARGE G. A. TURBOFANS (1500 Ib FN) GATE - SMALL G. A. TURBINES (150 -1000 SHP) GAP - G. A. PROPELLER TECHNOLOGY GOALS REDUCED AIC PRICE.AND OPERATING COST REDUCED FUEL USE LOW NOISE AND EMISSIONS Figure 1. - LeRC general aviation programs. ENGINE TYPE INTAKE & COOLING AIRCRAFT TEMPERATURE/HUMIDITY (4 &6 CYU CONTROLLED AUTOMOTIVE AMBIENT INTAKE (CHEV. V-8 & ROTARY) WATER-COOLED SINGLE-CYLINDER AMBIENTIHEATED INTAKE RESEARCH (DIESEL) WATER-COOLED DYNAMOMETER, hplrpm 3{XJ!SOOO 25014500 12515000 Figure 2. - General aviation reciprocating engine test facilities. 26 Figure 3(al. - View of aircraft engine test cell. 27 C-77-3619 Figure 3(bl. - View of control room. STOICH IO,,",ETR IC LEANED-OUT Figure 4. - IMEP instrumentation - 100 cycle bar-chart displays. CS-7f.,- lS 1 28 u u- Vl a:> 0 ae <: 0 z <: >- Vl <: ~ UJ U- 0 .... Vl z Q Vl Vl ~ u :I: .8r- .7 .6 .5 .4 .4 laJ 100 80 ro 40 aJ laJ 100 ,~FIA • 0.1 rFlA = 0.093 INCREASE DUE TO 6.FIA INCREASE DUE TO COMB. EFFEC TS aJL-. __ ~ __ ~ __ _L __ ~ ____ ~ ________ _ 50 60 70 80 90 AIR TEMP .. of Ill) EFFECT OF CONTROLLING FUEL/AIR RATIO TO CONS TANT VALUE AT 80% REL HUM. 100 Figure 5. - Taxi mode He emi, ns. -- GASOLINE ONLY --- HYDROGEN ENRICHMENT (GASOLINE-EQUIVALENT BSFCI NASA-LeRC JPL -.J -.-l_---L_---' . 6 .8 1.0 1.2.6 EQUIVALENCE RATiO Figure 6. - Effect of hydrogen en r ichment on fuel consumption. 29 J 1. 4 JOINT NASA/FAA PROGRAM AVCO-LYCOMING CONTRACT VARIABLE VALVE TIMING ULTRASONIC FUEL VAPORIZATIO ADVANCED IGNITION CONCEPTS TCM CONTRACT AIR INJECTION PULSED FUEl INJECTION IMPROVED COOLING COMB. CHAMBER CONTRACT FUEL TOLERANCE TESTS IN -HOUSE TEMPERATURE/HUMIDITY CORRELATION FOR EMISSIONS LEAN OPERATION (HEI. FUEL INJECTION) ADVANCED ENGINE CONCEPTS CONTR ACT LIGHTWEIGHT DIESEL CYLINDER (U. MICH) LIGHTWEIGHT DIESEL DESIGN STlJDY (TGPD) ROTARY ENGI E (CUTRISS-WRIGHTI STRATIFIED CHARGE ROTARY DESIGN STUDY ADVANCED SPARK IGNITIO ENGINE STlJDlcS IN-HOUSE LIGHTWEIGHT DIESEL OR STRATIFIED-CHARGE ENGINE WITH SEMI-INDEPENDENT TlJRBOCHARGER ROTARY ENGINE \ ITH SIMPLIFIED CHARGE STRATIFICA TlON SCHEMES COOLING FINS STUDY FOR ADVA CED CYL HEADS CO TlNUING OTTO PROGRAM DEVELOPMENT CO TlNUING DEVElOPMENT OF INSTRUMENTP.i ION AND CELLS Figu re 7. - Cu rrent programs. FUEL INJECTOR (PART OF IMPROVED FUEL INJECTION SYSTEM)- / / / / / INTAKE VAI.VE J ~ COMBUSTION '- CHAMBER r AIR SUP PLY FROM / PUMP FOR AFTER TREATMENT OF EMISSIONS '- VARIABLE TIMING IGNITION SYS IEM FOR LEAN F/A MIXTURE OPERATION Figure 8. - Advanced cylinder head concept integration. 30 . 6 u u.. VI .. 0 r PROJECTED RC-2-75 ,<", I .44 2400rpm(300hp)-' ""~/ 5500 rpm 9.5:1 C.R. 10 540 B 75% ,J'............ ~5 hpj 2400 rpm [235 hpJ--' .. -......,.... -- ~- . 4~':----::':----:c=------:-':-::------:-=---::-'. Figure 13. - Rotary engine fuel consumption trends. 33 1.00 L. .c I a.. :c co :£ z 0 i= a.. :;;; ::::> V> Z 0 U -' L.I.J ~ U u:: U L.I.J a.. V> L.I.J :.:: <: c:: .50 co .4020 IGNITION SOURCE INHERENT CHARACTERISTICS • MUlTiFUEl CAPABILITY • lEAN OPERATION • NO OCTANE/CETANE REQUIREMENT Figure 14. - Stratified-charge principle. I 50 r lYPICAl AUTOMOTIVE / DIESEL 70 BRAKE MEAN EFFECTIVE PRESSURE, psi Figure 15. - Rotary engine fuel consumption trends. 34 i' 100 .,. ""'0 ..-< vi C!> z :> /i th a bridge type side port being added. (Fig. 41) Fig. 41 shows the ~erformancc of the marinized 13 B engine. An approximately 50 PS increase will be gained over the current production engine. 56 Rotary Engine in Notor Sports (Fig. 42) In Japan, the enthusiast's interest in motor sports has shifted from the touring class races to the ones for the 2-seater class ... ,hich belonqs to FIA group 6. Fig. 42 shows the rotary N(:l.rch powered by this 13 B racing engine made its debut, September 1976 and triumph~d over the previously unrivaled BMW. (Fig. 43) The 13 B racing engine developed for the 2-seater racing machine is basically the same as the 12 A racing engine except it has a newly adopted dry sump as shown in Fig. 43 to lower the center of gravity. The metallic apex seals are installed on this 13 B racing engine. (Fig. 44) As shown Fig. 44, the rotor housing with the peripheral intake port used for the racing ~ngine is shown on the right side in comparison with the one on the left side with the side intake port for the production engine. The peripheral type intake port results in an outstanding volumetric efficiency at high speeds. (Fig. 45) It seems necessary to incorporate the special oil supply system as ~hown in Fig. 45 to improve lubricating performance at high eng~~? speeds when adopting the metallic apex seals. 57 (Fig. 46) We have been ~eveloping the rotary engine to make it more powerful by utilizing fuel injec"tion, among other things. Fig. 46 shows the testing of the Lucas type fuel injection system being carried out in our laboratory. 58 !, ~'" J t I., ~' ~ '" "t,_ )f ,~ " I,; Table 1 ENGINE SPECIFICATIONS ENGINE 121\ 13B GENERATING RADIUS (MM) 105 105 ECCENTRICITY (MM) 15 15 HOUSING WIDTH (MM) 70 80 SINGLE CHAMBER DISPLACEMENT X NUMBER OF ROTORS (ec) 573X2 654X2 MAX. POWER SAE gross (HP/RPM) 120/7000 135/6500 MAX. TORQUE SAE gross (LB-FT /RPM) 110/4000 128/4000 Table 2 FUEL ECONOMY AND EXHAUST EMISSIONS OF 75 AND 76 MODELS (EPA TEST RESULTS) '75 MODEL '76 MODEL ENGINE 12A 13B 12A 13B TRANSMISSION (MANUAL) 4-SPEED 4-SPEED 5-SPEED 5-SPEED VEHICLE RX-3 RX-4 RX-3 RX-4 & COSMO INERTIA WEIGHT (LB) 2750 3000 2750 3000 CITY 13.8 13.4 19.3 18.4 FUEL ECONOMY (MPG) HWY 20.0 20.5 29.6 28.8 COMB. 16.0 15.9 22.9 22.0 HC 0.';2 0.40 0.95 0.81 EXHAUST EMISSIONS (G/MILE) CO 3.92 5.39 7.44 4.98 NOx 1.16 1.09 1.60 1.68 59 Table 3 DEVELOPMENT IN ADVANCE PROGRAMS II SPARK PLUGS III COMBUSTION CHAMBER m GAS SEALS II AIR-FUEL SUPPLY SYSTEM Table 4 DEVELOPMENT OF CATALYTIC CONVERTER ~ OPTIMIZATION OF ENGINE AND ITS CONTROL I! REDUCTION OF BASE HC II OPTlfVlIZATION OF CATALYTIC CONVERTER SYSTEM II DEVELOPMENT OF CATALYST 60 I •. e ~:' Table 5 EXHAUST EMISSIONS AND FUEL ECONOMY OF ADVANCE ENGINE WITH CATALYTIC CONVERTER ENGINE: 12A(P-3), WITH EGR CATALYST :OXIDATION CATALYST(PELLET TYPE) TRANSMISSION: 5~PEEO MANUAL TRANSMISSION INERTIA WEIGHT:2750 LB EXHAUST EMISSIONS FTP 10 MODE 11 MODE (G/MllE) (G/KM) (G/TEST) HC 0.13-0.15 0.03-0.04 4.0-6.0 CO 0.5-1.2 0.2-0.3 10.0-15.0 NOx 0.80-0.93 0.19-0.22 2.7-4.0 FUEL ECONOMY FTP (MPG) CITY !22.0-23.0 HWY 29.0-30.0 COMB. 24.7-25.7 12A ENGINE 35x2 CID Figure 1 61 10 MODE 11 MODE (KM/l) (KM/l) 8.7-9.0 9.3-9.5 TWO-PIECE TYPE METALLIC APEX SEAL Figu re 2 ROTOR HOUSING CHROME PLATE J SHEET METAL C A.RBO" STEEL. I Figure 3 62 L:~~~E:~~.~~Y:~R •• [ SASE METAL SI P 7 4 MOOEL - DtE C ASTED ALUMINUM ALLO¥' 011GI1 TAL PA ~ h~ OF POOR Q Al ('I SHEET -METAL Figure 4 ORIGINAL PAG 0[.' POOR . E r QU J .-T PIN-POINT POROUS CHROME PLATED ROTOR HOUSING Figu re 5 63 SPECIAL Y SUR ACE TREATED SIDE HOUSING SPARK PLUG Figure 6 Fe-G-N COMPOUND LAYER U_~~\..II .... ~~L . r·~ 1" UF OL'I '75 MODEL '16 MODEL ~I 2 -GROUND ELECTRODES 3- GROUND ELECTRODES GAP : 0 .65 MM GAP : 1 .05 MM Figu re 7 64 FRICTION LOSS ANALYSIS 4.0r---·---------------------------------------- ~ 3.5 ~ ~ 3.0 W ::E u. \..J W 2.5 It: ::::I (J) (J) w If 2.0 ~ § u. 1.5 tb ~ w :a: 1.0 ~ B 1i: 0.5 u. MOTORING W.O.T. ENGINE:13B '75 MODEL ~O\LSEAL ____ ROTOn 0- -? ~ .... SHAFT AND BEARING(W!TH BALANCE WEIGHT) 1000 2000 3000 4000 5000 6000 ENGINE SPEED (RPM) Figure 8 MODIFICATION OF GAS SEAL ELEMENTS 6M 1.SMM 6M - O.4Mf.~ Figure 9 65 '74 & '75 MODEL '76 MODEL ] EFFECT OF MODIFIED GAS SEAL ELEMENTS 9~--------------------~ ".,;;'" /~'-'75 MOPEL TYPE / / 6 / ~ W.O.T. ENGINE :13B '75 MODEL TRAILING + LEADING SPARK PLUGS 5L.110~00~~20~O~0-3~0~OO-, -4000~--:5~0~00--:6~000~ 600 , ~ \ i" 500 \ o \ Q. , \ ENGINE SPEED (RPM) ENGINE :138 '75 MODEL LEADING SPARK PLUG ALONE ~ ~OO \ • -:.;:-'75 MODEL TYPE ~ ""- al 300 MODIFIED TYPE 200....-.---'-----1'-----'--~--'-' 1 234 5 6 BMEP (KG/eM2) Figure 10 MODIFICATION OF COMBUSTION RECESS AND SPARK PLUG LOCATION IY1DR LOR IE'--'--t-''-'''I L SPARK PLUG Figure 11 66 f. :' , 11 .' t< $' ~1 EFFECT OF COMBUSTION RECESS ON BSFC i '! ii, i, 600 1500 RPM ENGINE :12A '75 MODEL ~: r 1 f • i.i . A, 1~ it, < ., L SPARK PLUG ALONE ....... J: I UJ 500 a. ...... Cl -~' ~' : ~ 0 400 u. CJ) m 300 LOR C.R.: 9.4 ('76 MODEL) 200 1 2 3 4 5 t> BMEP (KG/CM2) Figure 12 EFFECT OF INLET CLOSING TIMING ON BMEP 9 W.O.T. _ I.C. (A~DC)j5' . ...a:,. " -..... 40' "''''''7'-'~ • Id' ,., '. , ~'P" }I" ',.. ~ , /; " ,',,-. !:'" II' , , 30'-'" :IE /hI ,\ ~ /, / 200 -./' \. (!) 7 11." \ l.\ ~. jf , , fll \ ~ I \ ~ I \ 6 J \ 8 5 ENGINE :12A '76 MODEL 1000· 2000 3000 4000 5000 6000 ENGINE SPEED (RPM) Figure 13 67 MODIFICATION OF EXHAUST PORT INSERT '75 MODEL (TYPE A) '76 MODEL (TYPE B) INSERT VOLUME: 33 cc INSERT VOLUME: 55 cc HEAT INSULATION RING AIR NOZZLE AIR NOZZLE ENGINE:13B 1500 RPM BMEP:1KG/CM 2 Figure 14 EFFECT OF SECONDARY AIR TEMPERATURE . ON THERMAL REACTION LIMIT 16 o 15 i= '" II: LI. :t 14 W Z (; Z W 13 ENGINE:13B '76 MODEL THERMAL REACTION LIMIT : < CO, HC=O,1 G/MIN '75 MODEL THERMAL REACTION ZONE 1500 RPM BMEP:3KG/CM' '76 MODEL 12 2~0~O~----~2~50-------3~00--~---3~50 SECONDARY AIR TEMPERATURE (OC) Figure 15 68 AIR CLEANER SECC~NDARY AIR PRE-HEATING SYSTEM AIR PUMP TO AIR NOZZLE Figure 16 t::::> SECONDARY AIR .... EXHAUST GAS HEAT EXCHANGER COMPARISON OF BSFC BETWEEN 75 AND 76 MODELS 900 , \ ENGINE: 12A WITH EMISSION CONTROL 800 \ -::I: 700 en a. C3 600 - o 500 u. en m 400 \ \ , \ \ V1500 RPM '75 MODEL \ \13000 RPM '75 MODEL 'ct ." , ~, "-~ ....... ....... ' .................... -- '-- 300 ................. -.----- --. -------. 1500 RPM '76 MODEL 200 3000 RPM '76 MODEL 1 234 5 BMep (KG/CM2) Figure 17 69 EFFECT OF COMBUSTION RECESS AND SPARK PLUG NUMBER ON BSFC, EXHAUST EMISSION AND EXHAUST GAS TEMPERATURE 300 290 ~ ti> 280 Q. ~ f! 270 en en 260 1500 RPM BMEP : 3KG/CM' ENGINE: 13B A/F: 16 SPARK ADVANCE: MBT 20 , 18 () 14 :r: 12 D COMB. RECESS :MDR COMP, RATIO: 9.2 • SPARKPLUG:T+L D' COMB. Rf-CESS:LDR , COMPo RATIO: 10.0 SPARK PLUG: L 10 r 8 ~ ~ ti> 6 Q. ........ ~ )( 4 0 Z 2 -.650 E w a:: ::J r-- t;: a:: w Q. :E ~ ~600 en c:x: (!) I- en ~ :r: X w !. 250 "'""-.....1.-'--..... 10 "'""_ ...... "-'---'- o "'""_--i ..... _...a.. 550 "'""_--i ..... _~ Figure 18 EFFECT OF SPARK PLUG NUMBER ON THERMAL REACTION z ~ ;:;... 0.35 eO.30 3: 9 IJ... 0: 0.25 ~ > 0: ~ C ~ 0.20 o W (J) 0.15 5.4 1500 RPM ENGINE: 13B '76 MODEL BMEP:3KG/CM' COMB. RECESS: MDR THERMAL REACTION ZONE : III 40 til til I- u i 0.04 w a: :::> (J) ~ 0.02 a: 0. ::.&:: oct W ENGINE:13B COMB. RECESS:LDR, C.R. 10.0 IG. SYSTEM:CONVENTIONAL L SPARK PLUG ALONE GAS SEAL:'76 MOOEL TYPE f I CONVENTIONAL SIDE PORT~I 2000 RPM BMEP:3KG/CM' ~I / / I I I I / CISC 0. 0~1~0----~1~2----~14~----~16~----1~8~ AlF RATIO Figure 31 76 EFFECT OF CISC ON BSFC 500 1500 R~M ADVANCE ENGINE: 138 .- ~ 400 CIt a.. ..... (!) - 350 () ~ CJ) 300 CD 250 200 1 2 3 4 5 BMEP (KG/eM') Figure 32 ROSCO REED VALVE PERIPHERAL PORT SIDE PORT MECHANICAL INJECTION PUMP INJECTION NOZZLE SPARK PLUG Figure 33 77 ;. ,. EFFECT OF ROSCO ON COMBUSTION STABILITY 0.12 ENGINE:13B 2000 RPM .... COMB. RECESS:LDR.C.R. ~9.2 BMEP:3KG/CM' 10. IG. SYST,EM:CONVENTIONAL ...... L SPARK PLUG ALONE ~ .GAS SEAL:'76 MODEL TYPE I ...... w 0.10 l- e:( / a: / z 0 0.08 / i= / e:( :::I /"- CARBURETOR I- 0 0.06 ::> ..J u. / w · ~/c---o-a: 0.04 :::I en -': ___ 7' R9SCO en w a: Q. 0.02 ~ e:( W Q. 0 11 12 13 14 15 16 17 A/F RATIO Figure 34 EFFECT OF ROSCO ON COMBUSTION STABILITY iii: 0: 0.12 § w ~ 0.10 cr .,.. (5 ~ 0.08 ~ ::> t; ::> Lt 0.06 w cr ::> ~ 0.04 W cr Q. ~ iil 0.02 Q. 2000 RPM BMEP:3KG/CM' AlF:14.B (STOICH) ENGINE: 138 COMB. RECESS: LOR, C.R. = 9.2 IG. SYSTEM: CONVENTIONAL L SPARK PLUG ALONE GAS SEAL: '76 MODEL TYPE o...o..._--- g Q. ~ 10 0 ELECTRONIC FUEL INJECTION FUEL INJECTOR INTAKE / MANIFOLD---" THROTTLE V,Jl.LVE THROTTLE VALVE Figure 36 IMPROVEMENT RATE OF FUEL ECONOMY ENGINE: ADVANCE ENGINE 12A EMISSION STANDARDS (G/M!I.E) HC 0.41 co 3.4 NOx 1.0 ~~--------~--------~--------~-------l~OO(KM/H) 20 40 60 80 ~O 7~ (MPH) ! ! ! ! 20 30 40 50 VEHICLE SPEED Figure 37 79 ~ 15 r Q. 10 .. o Z 05 VEHICLE DURABILITY TEST 0-- ' ~ • • • J' ~-- ENG ADVA ENG E 12A (P-l ) IITIA WEICHI 27S0 LB CAtALYS T OXIlAllON CATALYST WITH EGA MAX 9 -. CVS COLD -HOT :a:::a& " CVS HOT 40 r -81STo ~ 20 ~ &oF = 063 o 0 .~ ~ • • u o o _ _ ..5:!...~ COLD-HOT • ----- -=.:= := := := CVS HOT -1I1S1o ------------------------------------------------~ cvs COLo -H02-- __ _ _ of = 1 49 0 -~Q'--- - C-VSHO-T- - _ _ _ __ ~_"__"_O-------- --0---0- • __ __ -- - - • ('r 0.2 U 0 J: • ~ 0 • ~ ____ ~ ______ ~ ______ ~ ____ ~ ______ ~ ______ ~ ____ ~ ______ ~I(KM) 0 10.000 20000 30000 40000 ~o .ooo 60000 70.000 80.000 ~ ________ ~~ ________ ~ __________ ~ __________ ~ __________ ~I(MILE) 0 10.000 20 000 30.000 40 .000 50.000 AMA MODE ACCUMULATED MILEAGE Figure 38 MARH\!IZED 138 ENGINE Figu re 39 80 BRIDGE TYPE & STANDARD INTAKE PORTS -C/) 150 Q. - DC: W ;: o 100 D.. W C/) a: 0 :t: 50 IJJ ~ < a: m 0 , • I .. ~, Figure 40 MARINIZED 138 ENGINE PERFORMANCE ~-- ...... ~,- " ;" " ,," /' PRODUCTiON // ENGINE '/'/ ~~ f' ! ! , , , ! 1000 2000 3000 4000 5000 6000 7000 ENGINE SPEED (RPM) Figu ra 41 81 ROTARY MARCH Figure 42 138 RACING ENGINE Figure 43 82 SIDE POFn (PRODUCTION) PERIPHERAL PORT Figure 44 OIL SUPPLY SYSTEM THROUGH PER!PHEAAL PORTS OIL FROM OIL TANK ,"SUPPLIED DURING I DECELERATION I AT ABOVE ~OOO~P~ __ .:::..-__ ~~ PERIPH ERAL INTAKE PORT Figure 45 83 LUCAS TYPE UEL INJECTION Figure 46 84 UPDATE OF DEVELOPMENT ON THE NEW AUDI NSU ROTARY ENGINE GENERATION Richard van Basshuysen Audi NSU Auto Union N79~15965 Since 1971, AUDI NSU has developed a new generation of rotary engines with a chamber volume of 750 cc as a two rotor automotive powerplant, called KKM 871. This engine can be compared to a 3 liter or 183 cubic inch, six-cylinder reciprocating engine. In the following, the development and the current status will be presented. 1. GENERAL LAYOUT The general layout of the new rotary engine generation resulted out of the target to develop a comfort powerplant for passenger cars with front wheel drive. The geometric layout has been optimized by analytical and empirical investigations. Fig. 1 is a graph of this optimizing study showing the eccentricity as axis of ordinate, rotor radius as abscissa coordinate and rotor width as parameter lines g. The additional lines of parameter f represent constant specific intake port areas, only valid for an engine with side intake port. For the desired chamber volume a zone is defined, in which the most favourable range of engine geometry in respect to strength and structure is marked by the limitation lines a, b, c, d and e. Within this area of favourable engine design the KKM 871 has been selected with 17 mm eccentricity, 122,5 mm rotor radius and 69 mm rotor width. This results in sufficient safety margins to all limitation lines under consideration of an engine size as small as possible. This geometric layout was accompanied by thermodynamic calculations and investigations using simulation models. 2. ENGINE STRUCTURE Based on the preliminary examinations the engine has been deve- loped up to the current status as shown in Fig. 2 with the following characteristic features: - water cooling for engine housings - oil cooling for rotor, thermostatically controlled - dual side intake part, peripheral exhaust port - mixture preparation by Bosch-K-Jetronic- fuel injection system two fuel injection nozzles per bank - direct lubrication of the gas sealing 85 \~ \. - dual ignition with two separate ignition systems - dual scraper ring oil seal ex4aust emission control system with catalytic converter Fig. 3 shows a picture of a prototype experimental engine with the intake manifold for the K-Jetronic .• In the following various items of the structural configuration mentioned will be further explained. 2.1. Intake and exhaust system In the beginning of the development extensive comparison tests have been conducted between the same engine with peripheral and side intake port to find the most suitable intake system. The decision was made in favour of the double side port configuration that had already shown operational advantages in earlier NSU-experi- mental engines. The major factors that applied in this decision were: - far less sensitivity to the tuning of the exhaust system with aftertreatment devices less influence to the tuning of the intake system - lower induction noise - possibility of port timing of intake and exhaust with nearly no overlap and by favourable selection of engine geometry roughly the same perf~rmance as with the peripheral port configuration 2.2. Fuel injection system To realize a lean burn concept and according to basic investi- gations a standard Bosch-K-Jetronic, used for production 6-cylinder reciprocating engines has been selected. Fig. 4 shows the complete mixture supply system. The intake air quantity is metered by an air flow sensor installed in the mixture control unit. According to the volume of air metered, a fuel distributor apportions a specific fuel quantity via the injection nozzles into the combustion chamber. Since a fuel distributor with 6 exits is used both injection nozzles per chamber will be supplied with different fuel quantities: - the rotor housing injectio~ nozzle with two thirds of the total fuel per chamber, by connection of two exits. - the intake manifold injection nozzle with one third'of the fuel quantity per chamber by one distributor exit. 86 ;{ An electromagnetic start valve, placed at the common intake manifold, is under certain conditions injecting an additional quantity of fuel in case of engine starting. During the warm-up period an increased fuel quantity will be provided via a warm-up control. If, under this condition, the throttle valve is closed, supplementary air is inducted via the additional-air-valve for stabilization respectively increase of idling speed. The intake manifold shows a design, in which downstream of the common part each intake channel has a separate air supply. The two outer intake pipes, connected to the front and rear side housings are equipped with one intake manifold nozzle each, whereas the two pipes of the intermediate housing are without injection nozzles and therefore feeding air only. The coasting valve shown in Fig. 4 has the function to cut off the air under coasting condition,which is defined by closed throttle valve, gear and clutch engaged and engine speed above idling. By air-cut-off, the air-flow sensor in the mixture control is not ope~ating and thus the fmlsupply is interrupted. A more detailed illustration of the rotor housing injection nozzle is shown in Fig. 5. In difference to a standard fuel injection. this nozzle is provided with an air jacket. The air, selfinducted by such a configuration, is dir~cted radially onto the fuel jet via a narro\o/ gap at the tip of the nozzle. 2.3. Gas sealing lubrication system By using fuel injection it is no more pOSsible to apply a lubrication system based on oil/fUGl mixture. Consequently a new direct lubrication system for the gas sealing as shown in Fig. 5 has been developed. In this system oil and air as shown in section A-A will be supplied ~ia channels in the rotor housing to small recesses in the side housing. The lubrication oil thus entering the C9mbustion chamber will be distributed to the trochoid surface as well as to the side housing surfaces. 2.4. Ignition System The ignition system used is a transistorized coil ignition system with a considerably decreased inner resistance resulting in a steeper increase of voltage and less shunting effect. The energy storage becomes nearly independant from engine speed and by this the drop of ignition voltage capability at high speeds will be reduced. Fig. 6 shows the ignition voltage capability of a conventional and a transistorized coil ignition system in comparison to the range of the voltage requirement between a new and a used spark plug indicated by the cross hatched area. It is obvious that the transistorized ignition system offers a considerable higher safety margin. The two distributors, whicn are of conventional type, allow different ignition timings to be set for the leading and for the trailing spark plug. An inductive ignition timing control gU6rantees an accurate andfree-of-maintenance operation. Fig. 7 shows the position and design of the spark plugs as well as the configuration of the shooting holes. 87 . , I The trailing spark plug is provided with a narr.ow shooting hole by reason .of reducing the blow back aCross the apex seal tip. The center of this shooting hole is dislocated eccentrically to the opposite direction of rotor rotation. This results in a purposefully scavenging of the spark plug pre-chamber by fresh mixture and at the same time in a purification of this pre-chamber from deposites, that can be responsible for preignition. This effect is additidnally s~pported by a conical recess in~he spark plug face as i~ 6an be seen in' the dt'a\'trl up detail. Eoth spark plugs are of the surface gap type with an additional: ground electrode. 2.5. Rotor coolin~ and rotor desi~n I The KKr4 871 is provided with a thermostatically controlled rotor cooling for faster warm-up and for maintaining a higher temperature level on the rotor flank respectively rotor recess. This is a measure to improve the,mixture preparation in the combustion chamber and to decrease the friction losses. Fig. 8 indicates the effect of this control. The graph shows the different areas in which the oil jet will be open, closed. or regulating depending on engine speed and load. The design of the inner structure of the rotor has been modi- fied to realize a directed cooling oil flow as shown in principle in Fig. 9.' The cooling oil is injected into the rotor on the left side ~y the oil jet. In the areas below the apex seal groove the oil will flow over to the other side and than will be forced out.of the rotor by way of ribs. By such an oil flow system, the oil will pass mainly the areas of the sealing elements and by this the cooling effect is concentrated on the critical places. Fig. 10 shows the reduction of friction mean effective pressure with this new rotor/called thin film#type in comparison to the rotor with an interior cell structure used so far. 2.6. Exhaust emission control In respect to exhaust emission control for compliance with the US and Japanese requirements, systems with catalytic converters have been selected. Fig. 11 shows the principles of these systems differentiated into the United States version which includes a so called starting catalytic converter, and the Japanese version with one converter only. Looking at the US-system, the starting cata- lytic converter is locat~d close to the engine exhaust port to reach as fast as possible the reactio~ temperature needed. Currently this converter consists out of one catalyst per exhaust port ,and is provided with .a bypass. controlled by a flap. Under cold starting condition, the exhaust gas is directed through the starting converter and when engine oil and catalyst temperature reach a certain value, this converter will be bypassed and only the main converter will remain in function. The latter converter contains two catalysts located in-line with a short opacing in between. The separation into two segments serves for generating a more turbulent exhaust gas flow through the catalyst as well as for a faster warm-up. Presently used are metal stipport catalysts with platinum coating from the German Company Degussa. 88 _.""'''''1 _____________ •_____ "- ___ _ 1M .. " .• ' .. "U ••• 'd'tJl!lii __ •• a_Ir.". J~ ialliPMOSa(4SP, _441t sa_,- Due to the, richer air/fuel mixture under cold start condition it is still of an advantage and for the stringent US-standards necessary, to use an air-pump_ for secondary air injection. This air, however, will be cut off, if the water temperature exceeds 68 degrpe centigrade. 3. TEST RESULTS The following items present test results with the KKM 871, related mainly to the engine configuration described so far. The results also include some data of the different engine development stages and are explain.ed by means of fuel consumption. exhaust emission, noise emission and durability. 3.1. Engine Performance The performance at wide open throttle is sh<.:m in Fig. 12 indicating the maximum output at 6500 rpm of 165 horse power, a maximum EXEP of 130 PSI and a minimum specific fuel consumption of .51 Ibs/HP-HR. 3.2. Fuel Consumntion Concerning fuel consumption one of the main targets was to reach the level of comparable European reciprocating engines. This has been realized by improvements in the fields of: - mixture preparation - gas sealing system - friction losses - ignition - combustion 3.2.1 Ideal mixture ------------------ In respect to mixture ~reparation a principle investigation with a so called "ideal mixture" has been conducted to find cut, to what extent the lean out ability and the fuel consumption can be improved only by a perfect preparation of the air-fuel mixture. For this purpose a special test arrangement for ideal mixture formation as schematically shown in Fig. 13 was used. Hereby, the intake air as well as the fuel delivered by a fuel injection system, will be heated up sufficiently before both are forming an ideal mixture in a heated reservoi~. Out of this reservoir ahomogeneous charge of 70 de~ree centigrade will be inducted by the engine. Due to the homogenization, the cyclic variations of the air-fuel ratio are omitted. The high mixture temperature prevents a condensation of the fuel in the intake passage, which guarantees a uniform composition of the charge inducted. The test results with this system are shown in Fig. 14. At four characteristic points of the engine operating range, the specific fuel consumption is plotted over the excess air ratio. The engine with ideal mixture is compared with carburetted engines. 89 The m~asurements show a significant improvem~nt of lean OQt ability up to excess air ratios of 1.4 and a reduction of the minimum specific fuel consumption. 2~?-.!?-~_~E~j.E~_5:;p~!~~j.5:E_~j.~E_E=:!~~!'EE2-~_ The investigation with the ideal mixture h~s indicated, that a lean burn concept can be realized which now should be attained with a standard mixture preparation device. For this purpose the carburetor used so far has been replaced by the Bosch K-Jetronic. Experiments have shown, that with this fuel injection system the best results so far in respect to mixture preparation and driveability have been gained with the injection nozzles locatiOn shown already. It was also found. that an improvement of a~omization of the fuel jet, and by that, a lower penetrating depth could be realized with the annular air jacket of the rotor housing nozzle. As the nozzle is located close to the intake ports. where vacuum is always present, the air is self-inducted via'this air jacket and is reducing th~ fuel droplet size obviously. Fig. 15 shows the average test results with this system in comparison to engines with carburetor. The curves are very similar to those with the ideal mixture. This means nearly same lean out ability and a displacement of the minimum specific fuel consumption to higher excess air ratios, both requirements for a lean burn concept. Another comparison, sho\.;n in Fig. 16. where SFC is plotted versus BMEP &t 2000 rpm, demonRtrates the improvement in SFC related to the different development stages. The curves of the prototypes originate from engine versions without exhaust emission control systems. How the improvements in mixture preparation affect the fuel economy on the road shows a comparison test in Fig. 17. An increase of fuel economy under transient driving condition between 8 and 11 percent could be gained with the K-Jetronic compared ~ith the same engine equipped with carburetor. Fuel economy at constant speed in comparison to European cars with 6-cylinder reciprocating engines are shown in Fig. 18. Whereas the reciprocating engines, however, are only complying with the present European exhaust emission standards, the KKM 871 is equipped with an exhaust emission control system for future stringent US-standards. As shown by these results the target of fuel consumption eqUal to that of reciprocating engines has been realized by the measures applied so far. 3.3. Exhau3t Emission and fuel economy In the following, exhaust emission test results and the corresponding fuel economy data will be covered • The current disadvantage of rotary engines in respect to exhaust emissions is still the higher base emission of unburned hydrocarbons. Fig. 19 shows, that in the course of improvement of fuel consumption, the base emissions of hydrocarbons and carbon monoxides have been reduced considerably. Here the base emissions in the CVS tent cycle of the different prototypes II and III with carbur~tor and prototype IV with K-Jetronic. are compared. 90 • 1 .' , By comparing prototype II and III in respect to NO the increase was a result of improved combustion~ The reductionxreached again with prototype IV was gained by the lean burn concept. Although a remarkable reduction of the exhaust emissions has been obtained so far, the use of an aftertreatment system is still necessary. With the emission control system fer USA the test data as shown in Fig. 20 have been measured. All test data are below the Federal emission standards of 1981. In respect to CO the emission is far below the standards, so that no further problems should be expected. However it has still to be proven. that the HC-emissions will comply with the standards after the 50 000 miles endurance test. These endurance tests are still running at the time of this presentation. Concerning NO , the data represent a status of the engine without any s~ecial measure for reduction • Integrated in this diagram are- average values of measurements conducted by an US-automobile company in the United States with an engine and exhaust emission control system of the current development status. The test data from these measurements are within the range of the data specified by Audi NSU. For completion the corresponding values of the city fuel economy are added. In Fig. 21 the ranges of fuel economy in the City- and Highway- test and the combined fuel economy are shown. Indicated additionally are the measurements of the US-automobile co~pany confirming again our test data. For further information fuel economy data should be mentioned resulting out of a trip through the United States with two Audi NSU cars. The driving conditions over a total distance of approximately 2800 miles for e&c~ car includes city, high\oJay and test driving. The average fuel economy was 20.8 mpg with automatic transmission and 22.9 mpg with a 5-speed manual transmission. Measurements on highway driving only. have shown 24.4 mpg for the automatic and 27.6 mpg for the manual transmission car. With the exhaust emission control system for Japan, the ranges of test results in the 10-Mode test gained so far are shown in Fig. 22. In this diagram results of measurements conducted by a Japanese automobile company in Japan with an Audi NSU test vehicle are included. These data, however, 5how a somewhat higher NO -emission. Since the NO data represent values without exhaust gls recircula~ion, additi~nal investigation~ will be performed with £GR as well as with oxygen sensor control and three-wBrcatalysts to comply with the stringent 78 standards with a sufficient safety margine for production engines. Fig. 23 demonstrates, that in the Japanese 11-mode test the results are sufficiently below the standards of 1978. By this reason no further reduction, for instance by using a starting catalytic converter. is necessary. 91 The fuel economy measured during a trip through Japan with the Audi NSU test vehicle equipped with a 5-speed manual transmission has shown the following average values over a total distance of approximately 1440 miles: 19.5 mpg or 8,3 km/l including test driving and emission tests and 22,3 mpg or 9,5 km/l excluding test driving and emission tests. 3.4. Noise Emission Since the noise emission becomes more and more important, the rotary engine should ~lso be evaluated under this aspect. As already known, the rotary engine is advantageous in respect to low vibration and low mechanical noise. The latter becomes especially evident under road driving condition at higher engine speeds. Noise comparison tests have been conducted with a reciprocating engine and the KKM 871 both installed in the same car. Fig. 24 shows the test results due to the test requirements of the German Certification Authority, recorded under no load condition over the whole engine speed range from a point 7 meters sideways of the vehicle. It is obvious, that evaluating the dB(A) level, the rotary engine is lower in noise compared to the reciprocating engine due to its IO'/ler mechanical noise emission. Looking at the dBeB) lavel, which in difference to the dB (A) evaluates preferably the bass frequences, the lower mechanical noise level of the rotary engine comes into effect again at higher engine speeds. 3.5 Durability and wear Experiences with former production engines of Audi NSU in respect to durability and wear have led to a very thorough testing of the new engine. Fig. 25 shows the wear results out of numerous durability tests conducted with experimental engines of the different prototype verGions. Since the wear data over 62 000 miles shown can be related directly to the life time of the en8ine, equivalent durability as with reciprocating engines can be expected. 4. Conclusion The present development status of the KKM 871 at Audi NSU has shown, that in respect to fuel economy the level of comparable reciprocating engines was reached. Exhaust emission test data give the expectation to comply with future uS-Standards also after 50 000 miles. However, this has to be approved by means of actual endurance test results. In respect to the Japanese requirements further reduction of NO is necessary. The mechanical noise emission of the rotary engine acmonstrates t'ie advantaGe in respect to possible future restrictions. Results of comprehensive durability tests indicate engine life time equal to that of reciprocating cn~ines. 92 ~ z ~ 18.0 9 .m e'" >- .68 I- u 17.0 d - .66 0:: l- e' z w . 64 9 '" u u 16.0 w .62 15.0 .604.5 4.6 4.7 4.8 4.9 5.0 5.1 5.2 5.3 IN 115 120 125 130 135 MM ROTOR RADIUS Figure 1. - Design range for R. E. with 750 cc chamber volume. -- FUEL - -- - BYPASS AIR _ ._ .- VACUUM Figu re 3. - KKM 871 - test eng ine. FUEL DISTRIBUTOR ~==~~ .,J""'----FUEL AIR FILTER L..-......... COMtvlON i INTA,-(E T MANI F'OLD AIR ~igure 4. - Fuel and air supply system with K-jetronic. 94 MIXTURE CONTROL UNIT GWARM UP CONTROL \0 (]'I TENSION BOLT LUBR ICANT RECE SS l SIDE HOUSI NG --' ME TERING OIL .-.J. t>- FUEL 1\ - AIR INJECT ION NOZZ LE ~ RING CHANNEL (A IR) SECTION A-A , "- ROTOR HOUSING ! L - SIDE HOUSINGS-J -' L- ROTOR HOUSING Figure 5. - Fuel injection and gas sealing - lubrication system. 30 +---+---+---t----t--X-----;Ii---=r =-RA7-:-N-:-!;.SI STORI ZE D --1------0 COIL IGNITION (TSZ I ~ IGNITION' VOLTAGEQ-CA PABILI Ty---J COIL IGNITION W - -.. ------- I I~ o I I -----T---~ ~ ~~7~77-~~~-~T7~~-:~.~~~ ~ 20 ~-_+++_r~~~~~~~~~~ ~'----'-~~-SPARK GAP . ~ .0431N (1.1 Mrv1) z (USED PLUG) o I- z C) . CAR :RO 80 SPARK GAP ENGINE:KKM 871 .024IN(.6MM) 10+---t-----f-----+-- -t----+------+ (NEW PLUG) 1000 2000 3000 4000 5000 6000 ENGINE SPEED-RPM Figure 6. - Ign ition voltage capability and requirement depending on ignition system and spark gap. 96 SPARK PLUG INSERT TROCHOID SURFACE -+-i ~-+-.1 1 IN (2.8MM) ~---+--~.,----t----' f... .~--., 1.061N 1.46 IN ECCENTRICITY (27 MM) (37MM) "L" "Til DETAIL OF ROTOR HOUSING ROTOR SPARK PLUG DIRECTION OF WITH ROTATION SCAVENGING CONE Figure 7. - Arrangement of spa rk plugs. 97 U) CL 120 100 80 CL 4.5 60 w L al3.0 40 1.5 0 2000 OIL JET OIL JET REGULATING ENGINE SPEEQ-RPM i I 3000 4000 5000 6000 Figure 8. - Chari of oil jet control for rotor cooling. GEAR SIDE Figure 9. - Principle of cooling oil flow. 98 ~RECTION OF ~ CENTRIFUGAL FORCES ~ 1D Vl m 14 CL .9 .8 12 .7 10 CL UJ ~ .6 u.. 8 .5 -- .... 6 -- JY .4 -- .3 2000 --.c' THIN FILM TYPE ROTOR 3000 4000 5000 6000 ENGINE SPEf:D - R PM ------------------~ Figure 10. - Compar ison of friction-MEP. BYPASS CONTROL: TEMP OF START CONY .. .. ·~>950°C (17t.oo F lOR EN GINE WARM ---~- <950°C AND ENG COLD ~INTAKE MAIN CAT. CONY FIG. II.I USA-SYSTEM EXAUST CATALYTIC CONVERTER FIG. 11.2 JAPAN -SYSTEM Figure 11. - Exhaust em ission control system. 99 FUEL - 0:::: ~ ~ 180i..130 I 10 a... 8 w ~ 6 0:::: I I ~ :x:: --<.:> 420 u 380 ~340 300 -140 ~ 160 120 -"" 100 ........ / ....... 140 80 V .--a... I / ~ 120-0 V 100- i I 80 0:::: I I a... 60 I --~/ -40- .65 -- - . .60 .-' V 20 .5~_ -- .50 20CD 3000 4000 5000 6000 EN GI NE SPEED - RPM Figure 12. - Performance of KKM 871 at WOT. AI R HEATER 120 110 100 90~ 80 70 60 I- ~ 50 a... I- ~ 400 30 20 10 o DIAPHRAGM ~----'-." '-----LI RESERVOI R FOR IDEAL MIXTU RE FORMATION ENGI NE \ WEATER \ CONTR. FUEL METERIN G INJECTION NOZZLE HOT WATER JACKET ( K-J ET RO NIC) Figure 13. - Arrangement of ideal mixtu re formation system. 100 -J, o ~ :r: ~ ~ -C) 750 I -7 "'-£2 650 1--CL 0::: I I §: 900 110 if> 1.61 (23.3) CD --.J 1500 1:17 (17) ~5 600t1.00 \ I q U) \ ~.~,-rl ------ Z '\ :3 550 .90 \. ,~ " w 50 ::J LL 450 u LL 400 u W 0... 350 (J) .80 ..... ./ ----,"'" .70 , I I I .8 to 12 1.4 I I 1------. .60 .8 1.0 1.2 1.4 EXCESS AIR RATIO 2000 1.76 (25.5) ----IDEAL MIXTURE --CABURETIED ENGINE (AVERAGE) .-- I I --. .8 1.0 12 1.4 I I 1--' .8 1.0 1.2 1.4 Figure 14. - SFC at part load of R. E. with idea l mixture. I ~ ~ -<.9 I Z 0 ~ 0.... L ~ <..f) z 8 --' 0 -.J N W ~ LL U LL -U W 0.... <..f) 0:: I I 0.... ""'--9=-=0:-::-0-' 700i ~ 1.61 (23.3) 1:10 co 6501 -.J -+1-- 600-t1.n - ~ 5504- .9)--\\---+--- 500~ .80 , ___ ,,/ 450 I I .'il), , I 1 400 ~1 .8 1D 12 1.4 350 I .60 1500 1.17 (17) I / I , -Y----------y .8 1.0 12 1.4 EXCESS AIR RATIO 2000 1.76 (25.5) 300nrRPMl 2.35 (3L.Jjl ~ AVE~AGE CURVES - CARBURETOR ---- K-JE TRO NIC (+ENG.IMPROV) , , 8' n. _n10 12 1.4 , 1'0 12 1.4 . .8 ._ Figure 15. - SFC at part load depending on excess air ratio. 600 1. I 3: 0::: ~ (3550 .90 ~ , a.. 6 I i= 50 li'i ~ .80~ ::J V) 45 z 8 .70 .....J 400 w ::J u.. .50 0350 w a.. V) 300 .50 <.') a.. ~ , r ~ 0 z 0 U W .....J W ::J u.. \ \ \ ENGI NE KKM 871 \. \ ---- PROTOTyPE ][,CARB.WIO EECS \ \ - '- '-PROTOTYPEJIL CARB . WI D EECS -- PROTOTYPEN. K-JETR. W. EECS \\, \,', . , ",,' .... .,' .... . ............... ~, .......... ~-:---- ... -- ---.-==-:------.--- 20 4,0 5,0 1QO PSI 8,0 2 :3 BMEP 2. 5 6 '7 BAR Figure 16. - Specific fuel consumption at 2000 rpm. 2 1 .3% , 23.5 II 21.2 / I 20 8% , 18.9 17.5 111 // II 15 z 0 f- u 1D w -. Z gi 5 u.. / ROAD TEST : CIT Y OVERLAND MAX . SPEED : 311-1P H 62 MPH AVG . SPEED : 22MPH 37 MPH Figu re 17. - Comparison 0 fuel economy. 103 . , \ [,0 C) a... ~ I >- n KKM871 11 I 5-CYL-: RECIP. ENG. -.... (EU I~OPE,MOD .771 ~ 0 z 0 u w 20 ....J W :::l 15 LL 10 520 20 30 ! 40 L.p 50 7p 8.0 6'0 86 9.0 MPH 140 KM/H CAR SPEED Figure 18. - Fllel economy depending on car speed. ~ 2: a... 0... ~50 C) I ~ 1200 -- u x 110 0 z 1_ 100 u II. 90 80 3 70 50 20 50 I~O 30 10 20 10 0 PPO TOT {PE Figure 1 . - Reduction of base emissions (CV5 -t!!st results ). 104 FEDERAL 2.0 20 EMISSIO STANDARDS : ·1978 2.0 ~ r-, 1.8 16 1.6 ~ 1.4 ~ 1.2 ~ 1.0 ~ .8 ~ .6 I .4 16 14 ~ 12 ~ 10 0 8 u 6 4 "1981 I I I I I I I I I I 11.Oi'> i r-- --'i .90 1-; I . 1.68 15 r--l I 1 I I I I I I I I I I .2 o L-----·~~~~~~~~~~~---~~~~ O HC CO NOx FE 2 ~ AUD I NSU TEST DATA CJ US-AUTOMOBILE COMPAt Y TEST DATA Figure 20. - CVS -test exha~st em iss ion data and fuel economy. TEST VEHICLE : AUDI100 (3000 LBS.) 30 ENGINE : KKM871 25 20 C) Cl.. ~ I >-~ 15 o z o u W --.J 10 w :J U. 5 TRANSMISS:ON: MANUAL 5-SPEED 18.5 17.0 m AU DI NSU 26.5 20.5 ~ US-AUTOMOBILE COMP TEST DATA Figure 21. - FTP· fuel economy test data. 105 .10 ~ STAND~ RDS 1976 ~lf STANDAliDS 1978 If .25 If r---, I I I 1 2.1 * r-- l I I I I I I I I I I I I 1 .10 08 I I .07 . .06: o .04 He co I o ~ AU DI NSUTEST DATA .25 .1 9 .60 * r--'" I 1 I I 1 I I I NOx FE o JAPANESE AUTOM OBILE COMPANY TEST DATA (AVERAGE) FilJure ,2. - Japanese lO-mode test exhaust emission data and fuel economy. t- 8 T 80 t- ~ 7 70~ ~ 6 50~ (9 (9 I 5 50 I X 0 ~ 4 40 u I 3 30 u ~ STANDARD S 1978 7.0 * r---, I 1 I 4.5 4.2~- 50 r---' I I I 1 1 I I I I I I 2 20 1 I 10 11.91 I 4.4 r---l I I I I 1.61 2.0 1.5 1 11.1 12 0~--------~~~----~~~=·~1----~~ HC CO NOx 1&1 AUDI NSU TEST DATA IZI JAPANESE AUTOM O 81 LE COMPANY TEST DATA Figure 23. - Japanese ll -mode test exhaust emission data. 106 10 9-1 -8~ 7-;).. 66 5~ 4trl 3~ 2 :::) LL 1 o 90 ~ CD 80 o ...J 1 - RECIP E ~ 70+---1----. I.t-j'--+=---+---4-- ~ (5 z CD 90 en ~ 80+---1----+ -..J w Gj 70 -..J W 25 60'1-~"---I- Z ~+_-_+--1_-_4--1_-~- 1000 2000 3000 1.000 5000 6000 V') ~ t ~ 81.6 8 o .0600 a N a lO ::::: 11. __ ~ Z ~ O~- 12 1D .of.O .8 030 .6 020 .f. .010 .2 E GI E SPEED-RPM Figure 24. - Compamon of nOise l e~e, . WEAR LIMITS T o TROCHOID SURFACE rlgure 25. - Average wear da ta of durability tests . 107 REVIEW OF THE RHEIN-FLUGZEUGBAU WANKEL POWERED AIRCRAFT PROGRAM 1.) Introduction: Manfred R'iethm'ull er Audi NSU Auto Union N79-15966 The Rhein-Flugzeugbau GmbH hereinafter called RFB founded in 1956 is a division of the VFW-Fokker Aerospace Industries and their program includes among others the development of light aircraft with special emphasis on modern propulsion systems and production. Since 1971, RFB is working on the application of rotary engines to their aircraft program. Fig. 1 shows different types of aircrafts under the development of which the most interesting projects are the Fanliner and the Fantrainer. For both, the heart of the concept is the integrated ducted-fan propulsion system using rotary engines. The"decision for the application of rotary engines based on the general opinion, that only high rotating fans· could be used as integrated ducted-fans. Therefore RFB looked for engines with the capability to run at high revolutions. On the other hand, the powerplant should feature smaller space requirements than currently available conventional reciprocating engines, which were not modified in this respect since many years. The reason for the ne·ed of smaller engines was the installation of the powerplant behind the cockpit and to reduce the loss of some area in the hub region of the ducted-fan necessary for ventilation purposes of the engine compartment. Another reason was, that by using a rotary engine based on an automotive production version, the initial price would be low. I DC( 11 . 109 PAGE IN'JENTtoNALl Y BLANK 2. Fanliner Fig. 2 shows the Fanliner on the ground. The first Fanliner, that started flying in October 1973, was equipped with an Audi NSU two-rotor production rotary engine available as an automotive configu:t:.ation with 115 Horsepower at 6000 rpm dri'·i.ng an RFB three-bladed fan at full engine speed. In 1974 RFB fitted a 150 horsepower prototype engine from Audi NSU to the Fanliner. This engine was a former prototype version of the current KKM 871. The powerplant based on an automotive engine was progressively modified by RFB resulting in a second aircraft prototype rotary engine which took his first flight in 1975. At the beginning of flight testing it was found, however, that although the engine performance has shown very good results, the noise level of the whole propulsion system was too high, caused by the ducted-fan. For this reason RFB conducted several fan speed tests in flight and on the test bench with the result, that the high revolution of the ducted-fan can be lowered by means of a reduction gearbox without any loss of performance, but resulting in a much lower noise level that can comply with the limits of the German Federal Aviation Association called LBA. Present measured in flight noise at the rotary engines permitted full-throttle cruise during horizontal overflight at 1000 feet is 65 dB(A). That is about 7 dB(A) below the current German light-aircraft limit. With the new propulsion configuration about 440 flights with a total flying time of 220 hours have been conducted. 110 :/ { I f Ii ~'.,":"'----.- \' ~ II ., II IT ~t The present engine installed in the Fanliner and shown in the Fig. 3 delivers between 150 and 160 horsepower and has a wet engin,~ weight of 159 kg or approximately 350 pounds. It has to be mentioned, however. that this engine weight includes cast iron side housings as used for the automotive application. By changing these parts to aluminum material the weight can be reduced by approx. 20 kg respectively 45 pounds. On the other hand, since the engine is running at 6000 rpm and the ducted fan with 3000 rpm, there will be an additional weight for the reduction gearbox. For the modification of the automotive prototype engine as supplied by AUDI NSU into an aircraft engine the following items were changed. Fig. 4 a) The carburetor was replaced by a Bendix fuel injection system together with a new intake manifold shown in the picture. b) Several accessories such as generator, starter, fuel pump and some p.::rts of the ignition system into parts with LEA certification c) dual v-be It-drive d) and finally the flywheel with gear shows the engine from the spark plug side with the mounted reduction gear box. Since the engine is initially designed with two spark plugs per bank and two independant ignition circuits there is no necessity for additional spark plugs or a second ignition circuit for safety reasons. Experiences out of the flight tests have shown several advantages in respect to the rotary engine: ~~~~~~_E~~~~~~_~~~E~~~~E~~!~~ The lack of vibration translates into less fatigue for the occupants and less stress on the many connections holding the airplane together. 111 - ~~f~~_gl!~~ In contrast to the conventichal engine ther~ is no problem of engin~ blockage due to p piston seizure. This reduces the possib~.:ity of engine failure in flight. - ~~§~~l_~f!~~~~~~_~~~~~~~_~~~~~~~_~~~~~~_~!~~!~~~ The lean out ability without powerloss is much better than with reciprocating engines and there is no problem of overheating under this condition. The engine runs at full throttle also under cruise speed without any harm to the engine. ~~_~~~~_~~_!~~~_~~_~~~~~~~~l which means little wasted fuel and no delays in taxiing out to a take-ofl point and resulting in less wear on the engine itself. Although the fuel consumption of the KKM 871 aircraft engine with approx. 235 grams or .51 pounds per horse power and hour under 75 % WOT condition, is not as good as with reciprocating engines of similar output, this disadvantage will be compensated by better perfoFmance. In respect to fuel consumption it has to be mentioned. that this proto- tpye engine does not represent the updated features of the current Audi NSU KKM 871 automotive engine which includes f~ther measures for fuel consumption reduction. Since the decision for a production of the automotive engine has been delayed by Audi NSU, it beca'lle necessary for RFB to look out for alternative powerplants. It was found that for an installation in the Fanliner the following engines could be used which are listed with some data in Fig. 5: in the reciprocating engine field the Lycoming - 360 A3A and -320-H and in the rotary engine field the Mazda 13 B, but this engine only in connection with turbo charging up to 180 horsepower and the Citro~n rotary engine. 112 Although a final decision has not yet been made, the Citro~n rotary engine will be the most promising alternative in the moment taking also into consideration thrt CitroYn has tested the engine for about 800 hours already in respect to the FAA Part 33 for the purpose to obtain the certification of the engine as an aircraft propulsion system. The lycoming reciprocating engines have the disadvantage, that the installation space needed will result in a consiu~rably decreased area for the fan respectively fan blade length. A general comparison of t~e space pnd frontal area requirement between the rotary engines and reciprocating engines mentioned without the reduction gear box, show the following figures: in space approx. 14 cu ft will be needed for reciprocating engines compared to approx. 5 cu ft for the rotary engines This means the reciprocating engine would require roughly 3 times more space than the rotary·engines. in respect to the frontal area: approx. 820 sq in compared to approx. 460 sq in for the rotary engine which means roughly twice as much area needed for the reciprocating engine. This comparison indicates, that the rotary engine offers much more freedom in the layout of small air planes and especially for the design of the Fanliner chances are not good to apply a current reciprocating engine. 3. Fantrainer: Most of the items covered so far will also apply to the Fantrainer concept. The Fantrainer as shown in Fig. 6 in flight represents a two-seater utility trainer. 113 The development and testing is sponsered by the Germ~n Minister of Defense. The target of this program is the introduction of the novel fan-propulsion in connection with rotary engines and turbines for the task of an advanced and cost saving training of jet pilots. The Fantrainer was initially designed for the installation of the 4-rotor rotary engine with 300 horsepower developed by Mercedes-Benz and tested in their sports car called C 111. Since the production of this engine was cancelled and Audi NSU prototype rotary engines were available it was decided to use 2 of these engines with 150 Horsepower each, ·instead. The first flight with this configuration took place in October 1977. The arrangement of the two engines in the engine compartment is shown in principle in Fig. 7. The rotary engines are coupled via the gearb0x unit, driving the integrated ducted-fan. In case of failure of one engine, the disengagement automatically occurs by the free wheel clutch between the engines and gear box and the flight mission can be completed with the running engine. The investigation of the Twin-Engine Gearbox system as well as the development and production of the gear box will be performed by the Klockner-Humboldt-Deutz Company. Fig. 8 shows a Fantrainer mock-up with the actual installation of the propulsion system behind the cockpit and the configur~tion of the exhaust pipes. The complete powerplant is shown in Fig. 9. The two rotary engines are mounted one upon another and are connected by the reduction gear-box. The view from the intake and exhaust side indicates the intake manifold, fuel injection nozzle location and the shape of the exhaust pipes which are partially shielded. One engine has 4 injection nozzles located on each of the separate manifold tubes close to the rotor housing intake port. 114 ! ( Fig. 10 shews the powerplant from the spark plug side. This whole unit has a weight of approx. 300 kg or 660 pounds. With an output of 300 Horsepower, the Fantrainer reaches a cruise speed of approx. 200 mph. The flight performance drawn up in Fig. 11 shows the flight envelope, take-off and landing performance. climb performance, endurance, maximum range and thrust versus speed. These diagrams however show only theoretical values. Due to actual flight analysis it was found, that with the rotary engines KKM 871 in connection with the current ducted-fan an 8 to 10 percent better flight performance was obtained, which would not be possible at present by using reciprocating engines. In Fig. 12 a table is shown with different alternative powerplants for the Fantrainer concept, including several turbines, which, as indicated by the prices are much more expensive than reciprocating engines or modified rotary engines. For further development and testing of the Fantrainer the situation has changed in the meantime differently to that of the Fanliner. The comparison of different alternative powerplant becomes less interesting since the German minister of defence decided to use the turbine version of the Fantrainer with the Allison 250 C 20 turbine giving approx. 420 horsepower. RFB will in future apply only this powerplant to the Fantrainer. 4. Summary: The test hours conducted so far by RFB with the Audi NSU rotary engine KKM 871 in the Fanliner and Fantrainer amounts to a total of 423 hours. The number of actual flights amounts to a total of 707 flights. 115 :0 ! Due to the experience of RFB, the rotary engine has proved its capability as an engine for aircraft application with very good results and with the advantages of smooth running characteristic - no sudden engine failure - high effective mixture control versus altitude and no overheating by lean mixture. - good performance compens~ting the presently higher fuel consumption - low initial price by mass production of the basic engine for automotive application. Although the situation has changed for the Fantrainer in respect to rotary engine application, the Fanliner still will be equipped with rotary engines and the tests continqe. However, what type of rotary engine will be finally used is not decided yet. Furthermore it has to be mentioned, that the engines applied and tested so far are modified automotive rotary engines, which are not optimized in layout and design as an aircraft engine. /' . ---- -- .-._----_._------,------ . --'- -._-- -._------------ 116 VAA IAN TS ATI-2 • ",.hCopt. "otechO" • Aftt l .... -cOf!t ... ....,'" • COIN .... ..,,. RHEIN- FlUGZEUGBAU DEVELOPMENT FANLINER T ...,-'n Seet lttf't " "crl tt FANTRAINER AWI-2 • s.ttt1lwe T, • .,'M,.. • ... T,-.. n,,... • If A TnIt'"'" ATI-2-K1 • ~TreHM'" • eo...-. r ,....~.,. L ~:c-. "y, .. Figure 1 Figure 2 11 7 " ~11 ' 1'f'I1 lID III' ' rOOl.oCI ,oP'! St¥ ...... I'l l "'1"._I I,I~ ~tl!otCtlO" , ,, •• ' hr l C,. rIll' • T,..,...."..' .. otlftlli . .. I.--Nee ......... .~a.....T_ . l ..... " ..... Figure 3 Figure 4 118 Of,) 'V.{ , l-' \~~.!; • AllLIlIa ... 1- . . .. 11 ' C .... '- L,._ .. L' ...... (JOlt )J ai l t r h"'ulk U 171 hr~c~r ••• O-~ . , . ~-, .. -. QU4lv ~ Ii _.'-' ... h . tn· fl'y W. l ... hie t .... I Ihlt ". , .. ,..n " 160 110 110 110 160 It. ,th" t ... " 190 t ..... . . tt-..... r St ... . d •• ' ky 28, ~ '20 296 271 ' IS . ' I th ,,,", t a. l htrulu ." 16, 180 200 Y 'UU. ,.,.. 5t .t " .ua."t.4I' . ket t .; .. , ,,' ' ,' : ,2 6,0 ' , 2 JOe ... . 'uc: , . t.II. , h lt .,. 117 ,-, 17 4 ( 1&oK) 166 I H .. . . hut . , •• • l , t ... u c .. " l .4I"hl t en' •• • • • 1 • •• 1 ." In ,', 110 200ft .,h ,,- ,"" 170 1'2 !ml .. , F' 'l 8'00 It ." ,,, .. , I" 1'14 71. I" 71 ' •• tC' .... t • • • ,t. .. 1020 -. - . ) -.- . ) ,, 01\ 1100 _,t. ' ...... ,.\ . ... .. b;O -. - . ) - .-, "'" 70'1 TI -SST \,. ,... 7h Tr hh'. r h ... ,. l, te ' c..,.rt ~ •• • t ... , .. .. t 'nel Figure 5 Fig ure 6 119 III RHEIN - FLUGZCUGBAU THE FANTRAINER CONCEPT TN Mwt o' the F.tntf,1l'IIf oonc:epc tfi the Int ...... G.Ict.'1fI pn)OU"lOn ~"tm. Th'J lV«em tI ,.,... up of two 150 hp ..... .,.,.. coupled by • ,.,stbO- end cOnMt\1d to • ductld 'I" .... 1CtI "~'nl .... tld p« 1 of , .... t~ ... Inst eed of :he lWO .... It .......... ON Il,HbotNft .,...,,, IIrom .ao.""p up.IICtlI un , ItO be u_ TN dMtlCUftthCl of thtl pfOOl,ltStOn ptttem II. Yet)' Slfr"l., 10 ttl tnt'''" I "pt'OIIIM:tI"l In t'ilc"'-nt p"rfOtm 101 f.,n'" t 'lOt cocIo .... L Iv eN,..,... the _,..., .. of the Finer. . d ,Her.nt 'lMng 10Id.,"9' l i t «hte'llabtl The 'onow'ng Uble dftCnbH 1M po"tbl • ... ',.. • • ,.. comb~+OnII VERSIONS HotmlllWII''I Sm.II .. W,ng LM .... w,,. 2 . _04£....- AWU AWl .. IT...- All-Z All ·Z·KI ATI .. l_ Figure 7 . . . ~ "... If • • . ........ ,. - , ~. ~...../ /. Figure 8 120 J ... . \ G· 1. UALIT"1 :igure 9 Figure 10 121 Ait 10 ' S '0 Att!ftl • 1000 10 ' 0 SO FlIGH ' ENVElO ' E .., . • no., 'OG ,so 1110 ISO , ENDU~ 'NeE n • • ,.1 , ••• ,.,. tn .. 'I1'" +rt I • ,latt ' RHEIN - FLUGIEUG BAU FLIGHT PERFORMANCE ISA 0 ' 000 . 100 1400 W • lUX UNGE AU I tt l no "".1 r ••• , .,. . ' GOO 1",:1\01 '0_ 10 . 0 '000 lGOO •• " • C. .... , ' FANTRAINER AWI·2 Figure 11 ""''In ell .. ' I'(.,OIItoA .. a .., _1 ]SOk , 1100 +--+--+-l-~- AI, .0 1100 +--+--1l-l-~- .00 +-+--++ 400 II." SO oh )0 0 100 .00 SO 100 .so 100 If (kl. ' TH RUST VS S.((O h'O . )00 SH,. r-- ,,",",1 011 •• I'\. "- 9 " .. '10 JOO 110 . ,,,,., TRIEBWERK WANKELMOTOR HU8KOLBENMOTOR PROPELLERTlImlNE ENGINE WANKEL ROTARY ENG. PISTON ENGINE TURBOPROP AUOI NSU CITRO£N LYC 10 - 540 ALLISON PT6B-16 LYCOMING 102 Schtiban ~.2Scheiben 250 C 20 LTS 101 PS I U/Min 2.150 / 6000 19016000 30012700 410/6000 732/6230 595/6000 PS I RRM Vtrbrauch kp/PSh 0.~35 0.212 0.730 0.277 0.240 0.260 Consumption * Gewicht kp 270 290 230 80 150 120 Weight Preis OM -16000.- ? 20 000 - 80000.- 170 000.- 90000 Price 'Wasserkuhlun glq: 20 ? - - - -Watercooling Getr iebe kp 31 20 - -16 -20 -20 Gearbox .E, nbaugewichte .JI77~ AWI-2 I TRIEBWERK RHEIN - I ENGINE FLUGZEUGBAU GMBH Figu re 12 122 -> --:':'.y/, ~- ROTARY ENGINE DEVELOPMENTS AT CURTISS-WRIGHT OVER THE PAST 20 YEARS AND REVIEW OF GENERAL AVIATION ENGINE POTENTIAL Charles Jones Curtiss-Wright Corporation .. N79-15967 This paper will very briefly cover the range of Rotary Engine development work at Curtiss-\~right since 1958, revievl highlights of recent direct injected stratified results accomplished in the last few years, and discuss several aviation related engine trials, tests, and possible growth directions. The earlier technical material is drawn from more detailed SAE publications. Background, Development, History, and Popular Misconceptions The baseline standard has changed since Rotary Engine development activity started in this country twenty years ago. Energy and raw material conservation have taken on new import and cast the size and weight advantages of the Rotary Engine, for any application, in a new lignt: Figure 1 shows the relative weight picture in the engine size range applicable to General Aviation. The Rotary Engine is inherently a high power density machine because the ratio of working volume to total power section volume is high and the kinematics permit high speed. This speed capabili~y derives from unr-estricted intake and exhaust porting, absence of valve and drive system dynamics, complete balance with any number of rotors, non-reversal of the sealing element path. and a low rise of friction power with speed. Of course, smaller engine size and commensurate weight only translate into fuel consumption advantages in transport use if the engine has comparable efficiency. In addition, the engine must be durable and producible. The simplicity of the engine also introduces obstacles to attainment of the technical goals. The line-contact of the apex seals with the trochoid surface and the localization of heat input in the combustion zone require fundamentally 123 /' [~ I' sound design approaches to realize the full potential of th~ geometr'y . . " I I will briefly cover dural;lility and economy developmetlts at Curtiss-Wright and let the fact ,of over a million rotary automobiles address directly to the producibility issue. Taking the durability aspects first, it is true that when \'/e ran our first engine in 1959, where the seals were scaled from the NSU-Wankel dual rotating machine which was the starting point for all of these developments, seal life- spans were best measured in minutes. He It/ere able. holt/ever, to design sealing elements by mid 1959 which would wear out before they failed mechanically, although the I'\ are given in referenced NASA reports by Lockheed-Georgia, but the trends are similar to the following curves for homogeneous charge engines. A possible growth scenario for the RC2-75 is shown in Figure 44. Figures 45 and 46 expand the 10,000 RPM seal speed family to other sizes. Speeds up to 10,000 RPM are considered realizahle within current technology limits but d~require development. Rotational speeds to 12,000 RPM are predicated upon designed but not tested apex seals which retract from trochoid contact at high speed, thus reducing friction. Since leakage is a time function, a small controlled gap is considered acc~ptable. The trade-off here is somewhat different than the one discussed earlier for BSFC vs. BMEP rating. Increased rating with speed can be accomplished with only a moderate increase in component stresses if the Indicated'mean effective pressure (IMEP) is held to reasonable limits. However, there is no way that the brake fuel consumption 145 can be prevented from increasing with speed even though the rate of increase is less for the Rotary. Primary use of this capability would, therefore, be for improved take-off and climb performance of a given sized engine where cruise would then be at a lower than typical percentage of maximum speed. Closure The Rotary Engine has been developed to the point v/here it is a viable powerplant capable of a wider application range than any engine in use today. General Aviation usage is the most obvious application within this range. 146 Bibliography. Charles Jon'~s , Harold D. Lamping , Dav id H. My rs , Rober t W. Loyd" An Update of th Di ect Injected Stra t i fied Charge Rotary Comubstion Engine Developments at Cur i ss-\vrig t". SAE paper No. 770044, presented at SAE I nternational Automotive Engine _ring Congr ss , t-1arch , 1977. Charles Jone s , itA Progress Report on Cur tiss-Wright ' s Rotary Stra tif ied Charge Engine Developm nt" . SAE Paper No . 741206, Presented at SAE Internat ~o a1 Strat ified Charge Engine Conference , Oc tober, 1974 Charles Jones and Har ry Lamping , "Curtis s -Ivright ' s Development Status of the Strat ifip.d Cha rge Rotating Combus tion Engine". SAE Transaction 1971, Vol. 80, Paper No . 710582 . Charles Jones, "The Curtiss=Hright Rota ting Combus t ion Engines Today". SAE Transact i ons 1965 , Vol . 73, Paper No . 886d . Charles Jones, " New Rotating Combustion Powerplant Developme n t". SAE Transac tions 1966 , Vol . 74, Papel .0 . 640723 . Chaclf!_' Jones, "The Rotating CombustiOT1 Engin - Compact , Light\-leight Power for Aircraft". SAE Tr ansaction 1 966 , Vol. 76, Paper No . 67019 4 . Davit! E. Cole and Charles Jones , "Reduction of Emissions from the Curti.ss-Wrigt Rota,ting Combus t i on Engin with an Exhaus t Reac t o)."". SAE Transaction 1970 , Vol t 79 Paper No . 70074 . w:r. F ig rt, R.L . Leisenring and H.B . Silvestri, "The RC Engine .- A New Ap proadl Reduce Costs". SAE Paper No . 700273, presen ted at SAE National Air Tr snsportation Meeting, Apr i l, ] 970. Carles Jone s, itA surv(~y of Curtis:.;-Ivrigh t' s 1958-1971 Rotating Combus tion Engine Technologica l D ve l opment s ". Paper o . 720468 , presented at the l'at ional Automobi1p. Engineering Meeting , De troit, Hichigan , May, 1972 .Charle s Jones, "Development of the Rotary Engine", presented at the Rotary Engine Symposium , Detroit, Michigan, November, 1973 SME Paper No . t-1M73-650 . H. D . Lamping, M. W. Galliers , and S. W. Holosin, "Rota ry Combus tion Engine Trochoid Coating s and Seals" . SAE Paper No. 741043, presented at SAE Automobile Engineering Meeting , October , 1974 . A. Ciccarone, C. Antonini and U. Virgilio , "Fuel Consumption in Eut!opean Pas s enger Cars Powered by Gasoline , Diesel , and Direct Injection Stratified Ch"u 'ge Engines". SAE Paper o . 760796 , presented at Au tomob ile Engineering Meet ing, October, 1976 . W. T . Tierne, , E . f1itchel l , and M. Alp er s e in, "The Texaco Controlled-Combustion Sys cem, A St ratif ied Cha rge Concept , Review and Current Status", pr s nted a~ the Institution of Mechanical Engineers Powerp1ants and Future Fuels Meeting, January 1975 . 147 Bibliography (continued) H. Alperstein , G. H. Schafer , and F.J . Villforth , III , "Texaco ' s Stratified Charge Engin -lultifuel , Efficient , Clean , and Practical". SAE Paper 740563 , presented at Southern California Section Heeting , May , 1974. W ..T. Tierney, E.M. Johnson and N.R . Cralvford , "Energy Conservation of the V~hicle-Fuel-Refinery System" . SAE Paper No . 750673, presented at the Fuels and Lubricants Meeting , June , 1975 . \-1.T . Tierney and R.F . \-1ilson , "Adequate Future Trans ortation Demands Vehicle-Fue1-Refinery System Optimization Today", presented at the API l-tichigan Meeting, January, 1976 . R.F . Schaefer, "Application of the Rotating Combustlon Engine for Low Noise Level Aircraft ," Report No . 68-950l59-F, prepared under Contract No. N00019-68-C-01l6 by Curti s-Wright Corporation for the Department of the Navy, Naval At r Sys terns Conunand , July , 1968. H. Berkowitz, W. Hermes , .0 H20 Correcllon 0.92037 0 .89099 0.86617 0.86486 0 .86301 AlF·Spind l Ca rbo n &1. 12.954Ii7 8732 13.34775 13.33008 13.15666 A/F Sti •• nder O.ygen ~I. 12 .80934 0191 13.21285 13.21261 13.10602 Exhaust DenSIty , Ib /tt 3 0 .07374 0.07437 0.07439 0 .07439 0.07430 HC, lb/hr 2.88589 2.31 574 0.72492 0.74737 0.50824 CO, lb/hr 6 .09172 11 .36607 60.94562 48 .31582 34.64385 NO., lb"'r 0.001 G5 0.02997 2.18987 2.39977 0.25323 HC, Ib/Cycie 0 .011620 0.54034 0.00362 0.06228 0.05082 CO, lb /Cycie 0.20306 2.65185 0.30473 4.02632 3.46431 NO. , Ib/Cycle 0.00005 0.00699 0.01095 0 .19998 0.02532 DEMONSTRATED EPA STANDARD HC EmiSSIons. Ib /Cycle /R' led HP 0.00264 0.0019 CO Emi ssions, Ib /Cycle/Rated HP 0.03737 0.0420 NO. Emi ssions . Ib/Cycle /Raled HP 0.00085 0.0015 149 . 010 .010 .070 .010 SEAL WEAR .050 INCHES .040 .030 .020 HORSEPOWER Figure L - Specific weight com~arison wi:h turboshaft engines and Otto cycle gasoline engines . 1000 1000 1000 HOURS 4000 Figu re 2. - Apex sea l wear, RC 2-60. 150 1000 1000 u .. .. • -u 100 ' 0 • 0 10 60 ~O , ~ 10 u , ... 0 ::: . 0 1 0 6 0 ~ ,~ . I~ '" "001 "- " ~ - j-........ aw.,., ,. , " <' . ' . ......... '" ............... '" ....... ~ '. i""'-- J .. "U""" til' ...... r--.. ' " " . I 20 40 ~ 10 70 10 100 IIoI[P '" 2000 ,,, ... ~ I ........ )11M"" ,"I "-V '. " I ". '" ........... .......... ...... ~ .... i""'--J .. ~U .. "i ,u, ..... ", t:-: ~ I 20 30 40 ~ 60 10 s;) 100 IIoI( P 100 U ' 0 ... "' .0 • 70 I' 0 1.00 u to ... ~ IO 70 I ~ 0 I ~ .. 20 ' . 20 ........ -,- "- / ... ~, ." ~,-,-", I'. I' - 1-., J " " U" " tY III ' -. "::'- t':o • I 40 ~ 10 10 10 100 .... LI' . 400 .11 "", " I -" .. '" "- '. ......... . .. ..... 'I"'-''.a.. J ..... U .. ~y lin V ........ r--. ' " ' " '" 1 40 ~ 10 70 10 iOO I Mf P Figure 3. - SFC test results, January 1963, ReI -GO . ..... , ., • • , · ~ •• ·41 ... · '· o CJ o -CII- -; ,: ;~: Figure 4. - Basic engi ne components, RCI -60. 151 --' U1 N .-0 '7 ~ C~ 'acP '-~ , , 180 160 140 Q: ~ 120 0 Q. ~ 100 Q: ~ .. ~'-~'; \ \ ,'"" 0 "' Io. r 80 \,'"- UJ -..- . ~~ :Ie u.. U UJ Q. CI) UJ :Ie ... BRAKE MEAN EFFECTIVE PRESSU RI:: - P ~ I Figu re 6. - RC2-6Q part load fuel consu mption. 26 2~ 24 23 r RC2 · 0 BEST ECONOM". 22 21 Ii> RC2 . 60 20 19 18 17 16 I ~ 14 13 CI TY TRA FFIC A\lG 20 - 60 A\lG · ~ · 80 MPG MPG ~'~ 12 R C2 · 6 0 BE ST ECONOM Y 16 ., 228 11 9 RC2 - 60 1:\ 2 21 ., 17 6 STO \l - 8 . 6 2 21 II 17 I II 10 ~~l~--~----~----~--~--__ ~ 20 30 4 0 ~O 60 10 VEH ICLE SPEED - MILES PER HOUR Figure 7. - Automobile fuel economy with RC2-60 and standard V-8 production engi ne. 153 I Figure 8. - Lockheed Q-Star airplane with RC2-60 engine. Figure 9. - CeS!ina Cardinal airp lan e wi th RC2-60 engi ne. 154 Figu re 10. - Hughes helicopter with RC2-60 engine. Figu re II. - RCI -4- 3 engine. 155 Figure 12. - RC1 -1920 engine. assembly of power section. Figure 13. - RC4-60 engine. three-quarter , ea r view. carburetor side. 156 Figure 14. - RC2-75 enqine. Figure 15. - Rotor comparison, 4. 3 to 2500 cubic inch displacement. 157 INTAKE COMPRESSION IGNITION EXPANSIOli EXHAUST Figure 16. - Stratified charge combustion cycle of rotat ing combu stion engi ne. ollKT ( OMIUSTION (HAMln INJE(TlON ST . ' ... • - t"t· e" ~'. ~ • . '" -=----:-/ ~ .... ,I':~ . ~ • 'Of" .. '- TEXACO ~_..:..FO=RD:<..-~ STlli l1 ftcA flO. n '. 'fCllOt! '. TO INDUCED 4'1 SWill vUO ROTATION Figure 22. - Stratified charge RCI-ro. BTC plfot tandem ~LJa i. 162 1.1 2000 It ... t.I 0.. x , 0.. x .1 &, ... VII) -. ~..J v , . 7 ~~ ii • I~ z 0 U ..J ~ .5 Figure 23. - Current status of fuel consumption for stratified charge rotary engi nes. Figure 24. - Rotor pocket variation with compr 2ssion ratio. 163 tiC O}il p. lJv 4!., G°lt P (,) Q(; ~p ~ ~ L' I.JPy Without Insert '" X I 80 7 0 ~ 60 CD .... E .,. en 50 z o CD '" " u ~ 40 o .. X ..J ~ 30 20 10 COMPo RATIO ~ 0 I". :: o--~ 8.5 6 _ _ _ 10.5 \ \ ! I \~t \ ~\ 8SFC • I ~ \ I ~::u... ' \ ----=r-~ \ \ , I \ \ \ \ \ \ 8.5: I COMPo RATIO I 0 .5: I COMP RATIO \ \ \ , 8SHC '-..-" -~ .... ""-. -.." °0~----~2~O~--~.~O----~6~0-----=80~--~'OO 8MEP-PSI Figure 25. - Effect of compression ral io on fuel consu mption and exhausl hydr arbons. Assembled - after lest ~i9LJ r e 26 . Bolt ' on hot Insert retor. 164 a: :I: ct 20 :I: II) ..... o I U) ~ 16 en U) i w z 12 ~ ~ u o ~ 8 >- :I: U ~ u ~ 4 U) W :III: C( a: 2000 RPM TANDEM DUAL. BTC PILOT. ATC MAIN ROTOR HOUSING .nt!.C M,---,----------,-------------------------, 16 a: 12 :z: I ... :z: !!? 1" u :z: l3 8 STANDA RD ROTOR ITESTEO WITH BTC MAIN NOZZLE I STANOARO ROTOR 1975 HOT ROTOR IT·SLOTI 1976 HOT ROTOR IBOLT-oN I o~ ______ ~ ______ ~ ______ ~ ______ ~ ______ ~ o 40 10 BMEP-PSI Figure 27. - Specific hydrocarbon emissions with standard and hot -i nsert rotors. 2000 RPM \ \ \ TANDEM DUAL, BTC PILOT ROTOR HOUSING \ \ \ x \ ~ \ \ \ \" I \ " \ ' ~ TYPICAL ROAD I.OAD BMEP RC2-60 CARBURET-rED OCT. '75 T-SLOT HOT ROTOR GASOLINE JP5 DIESEL 100 II) O~----~~----~~--~~----~~----~------~----~~----~--~ o Figure 28. - Speci fic hydrocarbon emi ssions. 165 a: l: I Cl. l: CD ..... CD ...J I z 0 ~ Cl. ~ ~ en z 0 U ...J I&J ~ "- u ~ u I&J Cl. en I&J lI: ~ a: CD ~ ... % 50 E 'I) :: z Q ~ i ... Z JO i a:: c( g a:: o > % 20 !:! ... U ... ~ o ... 10 !;( (J o ~ 2000 RPM '" - "PILOT ONL Y" ATC, RECESSEO, UPSTREAM INJECTION \ \ _____ --6- - o~------~------~------~------~--------~------~------~ 1.50 .90 .80 .70 .60 . 50 .40 .30 o 20 60 80 100 120 INDICATED MEAN EFFECTIVE PRESSURE·psi Figu re 29. - Indicated specific hydrocarbon emissions comparison of different pi lot locations. COMPARISON DATA-COMET MK V DIESEL ALUMINUM ROTOR HOUSING , 1975 CAST I RON ROTOR HOUSING,I976 . RCI-60 S.C.J 2000 RPM PROJECTED S.C. 1'1) 10 20 30 40 50 60 70 80 90 100 BRAKE MEAN EFFECTIVE PRESSURE - PS I Figure 30. - Part load fuel consumption. 166 70 30 ALL ' llATA III SPECTRUM 1EV!U 50 100 200 fRE'lJ£NCY (Hz) Q - gru (WAIIICEL I RUII NO . 3, 2/20/70 AU. 126' lAS - 57 ICII"l'S RPM - 2375 M. P. - 18...2 T/O Ifl' - 2661 3-BUJl!, 12" CHORD 1000 Figure 31. - Q-Star noise spectru m. Figure 32. - RC 2-60-Y8, Q-Star installati on details. 167 1 GIN. L P.\ rE P Pcll PALl Y 2000 J • \ A • .. • • I I I ill n. - ~ ; t·. ~ '. I - ~ II ' I . : , • LLh' TQP CVWI · ~_LJ 1l1~ . .-t--' ! _ 1- - , , : 1- 1 ~ I Iii ~ ~! : ' I i I CIIIN'CIIm or ..n ~ 100ft 'LIft us PDT ~L ~ '- , -----t- 11-17 . .. CAS. 2100 _ . I . _ ... _lI'OU ,.._ , , , j .. . • j f-I+ ~.- - y\- , -IT , I i - - j' , • ,. , , !- _ l ... : • : '1- - l- i VW\ IA . ! i ~ . , : I : ' , . ~ Itt .. ;-\ \ V , ,- ! -I;- ~ ... 1'1 : I I I .. ,1 -I - ...! - '-.- ~ \ • L I I t-r- r- - "I .- ~ I- .... I • ! 1""" ~ j • .. ,. ~' ~f.~ 11 ~f- ~~ ~ ~ . I ~ ill.. !. r- ~ ~ ~ ~~~ i'oo. if - f.--L.. , ~ ~ ~r ... I :: ! ~ .. : ~ : ,,, ! .. : ! ~ ~ ~ I fo ... , I ,. ~--~ I , I I Ii ~ _. f-- I 1--,-- . .:. - I - f- UNlI COWl : J _ i. ..i.... -.- Ie ,. .- - - -- eJ.wGI m or .,1Ir\I ~ .aunt n.nT In PUT /lGL ,. " "OIIIL In. Kl - 60 IIC_ ... 00 _ • 1' . 2 OIc.S lie I ~ . .... "OUI ,. • ..,. -,. i , r · :~:t :J · '.j I 1 . ' , ~ I.' !' "'"1-- i ,.1 1 ·: .!; - - r-:-. : ' ' • , ••• , •• f , ) • , •• f , .. ' - . - .. - -ntaOUIHCY IN CYCLI. ~III •• COHD Figure 34. - Cessna 177, standard prop II r speed installation. 168 p tt; l~ i . [ fJ'f Figure 35. - RC2-60-Y8 eng ine, aircraft carburetor, modified ignition, and manifold ing. FULL THROTTLE PERFORMANCE 60· F, 29.92 in. Hg Dry FULL RICH MIXTURES CMI.- MARVEL SCHEIILER HA-6 AlIt CLEANER - FRAM 5116606 FUEL-NO LUD AMOCO REG. + 1"- HAV, IOWJO OIL - HAVOLINE IOW30 MU .... LER - OLDIERG (CW-676 - 2A) IENDIlI 12 V C.D. IGNITION - TIMER SIN •• S .. ARK .. LUGS - 'IS-lSI COOLANT - 44"- PRESTONE I WATER 10 r ~ 110 I i 160 ~ 140 -' MAiNSHAFT SPEED - 'p", Figure jO. - RC2-60-Y8 test stano perfor mance. 169 160 140 120 100 BRAKE HP 80 60 40 BARf: ENGINE 60°F. 29.92 in H9 DRY 140 120 VOL. EFF. -% TO RQUE 100 Ib ,ft 80 L-~----~----~----~-----L--~60 3000 4000 5000 6000 7000 8000 MAINS HAFT SPEED - rpm Figure 37. - RCl -60, per ipheral port engine, performance at higher speeds. Figure 38. - RC2-75 e gi ne on propeller test stand. P b.UB IS ; Q D t\lJrr'l 170 -; I 00 c: o ~ 1200 co " , 1100 c: E 1000 a. a. 900 Z 0 800 ;:: - z 600 '" u ~OO z 0 u 00 z 0 300 III a: :t: a 1000 2000 3000 1000 15" Hg M AN V AC. zono RPM ~. H g "AN. VA C. 000 2000 301)0 Figure 39. - RC2-60U5 and automotive V-8 engine raw emissions as function of engine speed. FULL THRC'HLE STANDARD DAY PERFORMANCE 350 BTC IONITION TIMING BEST POWER · .073 fl. .. ~ ...... £ ~ 0 ...I U. a: ~ en z 0 U ...I w .. :::l'; u.~ . :I: UCD w __ ~.c <1)- w ~ < a: CD 2400 r '''''''' L ~" ~ I z.~C-J ' 1800 1600 1400 1200 BS FC ~ I .58 .56 .54 .52 .50 I I 3500 4000 4500 5000 5500 6000 MAINSHAFT SPEED · rpm Figure 40. - RC2-75 full throttle performance, 7.5d compression ratio. 171 JOO 280 260 240 220 200 180 160 ~ :I: CD a: w ~ ~ ~ A- % .I! ,Q I <.J ... :g .10 ~ A- % . 61 .I! ,Q Z .5. 0 ~ A- ~ ::I .54 III Z 0 <.J ..J .52 w ::I 4 ... ~ . ... .50 U w ~ w . " c( cc III . . OM 77% POWER, 55° BTC IGNITION TIMING 7.5:1 C.R. SYM. ROTOR $TO SIP .63" RET • RC2·75 AT 77% POWER .061 .012 .066 FUEL · AIR RATIO ' .6: C.R. TRAILING ROTOR MOOIFIEO OUENCH STO SIP .63" RET . ' .5 :1 C.R . SYM. ROTOR STD SIP .63" RET . - ' .5:1 C.R. SYM. ROTOR SURFACE GAP SIP .36" RET. 8.5:1 C.R. SYM. ROTOR SURFACE GAP SIP .040" RET . .070 .074 .078 Figure 41. - RCl-75 cruise fuel consumption. 75% C:~UISE ENGINE MODEl X RC2·75 o RC2·75 A RC2-75 o RC2-75 T.O. RATING IHP 1 RPM .54 X 5600 RPM NASA CONT. NO. NASJ·20030 RPT. NO. CR ·135119 o 1()'540 A,I ,E,G + 1()'540 C,J 285 1 fJOO/J 285 1 fJOO/J 286 / 5600 330 15600 280 1 2575 250 1 2575 280 1 2700 lOCI 1 2700 .52 .50 .48 .46 .44 .42 .40 7.S EFFECT OF SPARK PLUG RETRACTION I,,; , ANTICIPATED RESULTS, ; ' ... t BR AKE MEAN EFFECTIVE PRESSURE _ Figure 43. - Effects of decreasing strat ified charge rotary engine displacement with cor responding i,1crease in degree of turbocharging. GASOLINE FUELEO REDUCTION DRIVE 700 ADVANCED MODEL , NORMAL WEIGHT INCLUDES · NEXT STEP?, BASIC ENGINE 1 / )( MAGNETO FUEL MEETERING SYSTEM 600 FLYWHEEL AND STARTER OIL COOLER DRY OIL TANK ~:OOLANT COOLER 500 COOL ANT IN ENGINE ~ 400,1-----~~----~~~~--~------4_------+_----~ 10.1 ~ 10.1 (/) ~ o X 10.1 ~ Cl ~ ,----t- WEIGHT --1---- -........ I ' OROWTH WITH SPEED INCREASE 300 GROWTH WITH FUEL INJECTION - INITIAL MODEL - CARBURETTED CD 200L-----~------~------L-----~------~----~ 6000 7000 8000 9000 10000 11 000 12000 ENGINE SPEED - RPM Figure 44 - RC2-7.~ output gr()N\h esti mates, carbureted. 173 BASED ON 10,000 RPM RCI-60 EOUIVALENT SEAL SPEED AND 470 BHP • 10,000 RPM FOR RC2 - 75 WITH REDUCED FHP 2000 , 0 -; 1500 l a:: - 1000 a w w 4- IJ) w z ~ w a:: w ~ w IJ) a:: 0 :r w l<: C[ a:: II) 800 600 500 400 300 250 200 150 100 10 15 20 25 30 40 50 70 90 150 DISPLACEMENT PER ROTOR - IN] Figu re 45. - Est imated RC engi ne power and speed. BASED ON 10,000 RPM RCI-60 EOUIVALENT SEAL SPEED AND 470 BHP C 10,000 RPM FOR RC2 - 75 WITH REDUCED FHP 2500r---------------------------- 2000 1500 IJ) II) -l I ~I OOO C) w 800 ~ w z 600 Ci z 500 W -l 400 C[ 2 a:: 0 300 z 200 I/') ... 20 I N ... $ U / a:: / I- I Il. , 15 'T N / U :r / w a:: 0 / 2 Il. ... / 10 ~ J: "" 8 ~ "" 1/ 7 9 I / I / ' I '" 1/ .- 1 /' I / .-, ,- I I -7 15 20 25 30 40 50 60 80 100 DISPLACEMENT PER ROTOR - IN.] 6 ~ z 5 W W 4 ~ C) z W 3 150 200 Figure 46. - Estimated high speed RC2-X RC engine weight and size. 174 N79-15968 ENGINE REQUIREMENTS FOR FUTURE GENERAL AVIATION AIRCRAFT Joseph W. Stickle NASA Langley Research Center The emphasis of papers in this symposium has been on rotary engine test experience with projections of technology improvements that make the rotary concept very attractive for aircraft applications. The market and competition for the rotary engine, hO\,/ever, is not today's aircraft fleet nor the current technology piston or turbine engine. Each of these factors will be changing to adapt to economic and environmental constraints of the future. The intent of this paper is to examine the market place for general aviation aircraft into 1980's and indicate the visible constraints that engine manufacturers regardless of the type of cycle will have to face. Since 1972 the general aviation industry has enjoyed a steady and healthy expansion, approaching 15 percent per year. Projections by Government and industry indicate a continued growth through the 1980's with guarded optimism over fuel costs and availability and noise constraints. Figure 1 illustrates the growth in sales value over the past several years and indicates the growing importance of general aviation to the U.S. aerospace economy. Last year for instance, general aviation sales exceeded $1.5 billion which is about one-half of the value of transport aircraft sales. General aviation also contributed ab6ut $0.5 billion in favorable balance of trade with 25 percent of the over 15,000 aircraft manufactured in 1977 being exported. '75 The ~iorl d-wde fl eet of g'enera 1 av; ati on a i rp 1 anes now exceeds 250,000 airplanes with the U.S. fleet being the single largest at 161,000. Figure 2 shows the projected growth of the U.S. general aviation fleet to reach about 245,000 by 1985 or almost equal to today's world fleet. In order to maintain perspective, however, one might recall that in 1975 there were 6.8 million U.S. automobiles manufactured and that by '19'85 the manufacturing rate '1s projectf~d to increase to 9.2 million per year. The point is that while the aircraft fleet has a healthy growth projection, the total aircraft engine market is very small compared to the automotive market. This added to the fact that airplane engines have historically been better maintained and tuned than auto/native engines indicates a formidable challenge for the introduction of any alternate engine cycle into the aircl"aft market. A factor in the projected fleet which could favor the rotary engine is the trend in utilization of general aviation~ General aviation is involved in the eight classes or categories of flYi~~-i~~luding: personal transportation, business, air taxi, and rentals for the comm~ter aircraft, special purpose aircraft (such as pipeline survey and agricultural aircraft), instructional, sport, and proficiency flying. About 65 percent of general aviation flying is spent in what is called point-to-point travel. That is, the person who wants to get in his airplane and go from point A to point B and get there safely, reliably and these days more economically. Operating economy or efficiency will be a key factor in the future of the general aviation. Business flying appears to be the largest single growth area. 176 With the airlines dropping service to the lower density cOlTVnunities, general aviation business flying will pick up. The businessman is more schedule dependent than the pleasure flyer and therefore is more likely to be equipped for flying in adverse weather. FAA projections shown in figure 3 indicate a two-fold increase in inst~ument operations between 1975 and 1987. In 1975, general aviation accounted for about 45 percent of the instrument operations in the United Statesai"id the air carriers about 45 percent. But by 1986 general aviation is projected to grow to about 65 percent. The t~end is clearly toward the use of general aviation for business and transportation where schedule reliability and service dependability are of prime importance. Following this trend will be an increase in the number of pressurized aircraft and air condition systems for improved safety and comfort which add to the auxiliary power requirement. This means taking needed horsepower off the propulsive engine. Turbines and perhaps high power rotary engines would appear to have an advantage over the piston engine for power extraction due to their lighter weights. Trends in engine weight as a function of the horsepower are shown on figure 4 for piston and turbine engines. Piston engine weights fall between 1.5 and 2 pounds per horsepower while the turboprop engines are slightly less than 1 pound per horsepower. One of the rotary engine goals mentioned in an earlier paper at the symposium was 1 horsepower per pound. This achievement in a reliable, cost competitive version would provide a real challenge for the aircraft engine market. 177 Turning now to constraining factors for aircraft of the future, environmental impact appears to be a major concern. Recent federal actions have removed the emissions standards for general aviation piston engine aircraft, but the noise constraint continues to increase. The current FAA flyover noise rule for propeller-driven aircraft (FAR 36-F) is shown in figure 5. Noise measurements of the current general aviation fleet fall within a band of about ± 5 db from the noise rule as indic~ted by the shaded area. There have been several programs from early 1940·s up to very recently involving experimental vehicles in which the engines have been highly muffled and the propellers have been slowly rotated to reduce levels to 70 db or below. The performance and cost penalties for this level of suppression would be prohibitive to the utility of the general aviation aircraft and to its sales in today·s market. As a matter of reference the lower shaded area shows the level of non-propulsive or aerodynamic noise associated with this class of airplane and indicates that the noise which is of concern to the airport and surrounding communities is related to the propulsion system. NASA, in its noise reduction research, is now concentrating on technology that will provide up to 5 db reduction with a minimum of penalty that can be applied to aircraft over the next decade. Examples of this I~esearch include development of more efficient propellers, evaluating free versus shrouded propulsion systems and techniques to quieten the engine noise. Interior noise is also seen as a major constraint as general cabins are recognized as a high noise environment for both crew and passengers in a comparison of public transportation modes. The same technologies that reduce exterior propulsion noise should also improve interior noise levels although additional treatment to the airframe and cabin environment is needed and is being researched. 178 " Efficiency is a second major constraint seen for general aviation. From a historical view, the improvement in aerodynamics for general aviation aircraft have not been overly impressive. Figure 6 shows the trend in lift-to-drag (LID) ratio, which is a measure of the efficiency that has evolved since the very early 1920 ' s. These aiY':raft have maximum L/D's in the order of 8 to just over 14. As a point of comparison the L/Dmax for some of the transport aircraft of today are in the range of 16 to 18 so there is room for improvement and a potential for advanced future general aviation aircraft that operate at L/D's of 18 to 20. Some recent examples of aircraft good aerodynamic design and innovation include the Bellanca skyrocket and the Vari-Eze. Both of these are all composite airplanes. The skyrocket, figure 7, holds the world speed record for a piston engine airplane of 327 miles an hour. Its cruise drag coefficient is comparable to today's modern jet transports. Figure 8 is a photograph of the Rutan Aircraft Company's Vari-Eze airplane. It has a very high aspect ratio, a lifting canard in front of the wing which eliminates the download carried by a conventional tail, and it incorporates other advanced aerodynamics, such as winglets and a new airfoil section. The Vari-Eze cruises at 138 miles per hour on a 75 horsepower motor and is reportedly achieving over 70 miles per gallon. A third consideration of efficiency is one I call payload carrying efficiency. Figure 9 is a plot sho\'ling the fuel mileage versus payload at maximum fuel load for various aircraft. The typical piston-powered single-engine airplanes are providing from 10 up to 18 or 19 miles per gallon which is pretty economical in terms of personal transportation but 179 , , ! I) with payloads generally less than 1,000 pounds. Adding a second engine to the airplane does not necessarily result in greater payload, ~ut it does cut the fuel efficiency at least in half. For turboprop powered aircraft, the fuel efficiency drops to a level of between 5 and 2 miles per gallon. There are airplanes flying today that are so weight limited that if loaded to full fuel there is no payload at all. In this case the crew establishes the payload and. then must determine the range that it will be carrying. An interest-jng thought for the future involves the tradeoff between re 1 i abil ity and operati n9 cost of a twi n-engi ne pi ston- driven aircraft ~ompared to a single-engine turboprop. The turboprop engines have a much higher time between overhaul and are noted for very high reliability. Single-engine turboprops are being used in the agricultural industry with surprisingly good success. There are about 7,000 aircraft in the U.S. agricultural aircraft fleet and about 1,400 of them are produced each year. These airplanes,when they are working, operate 16 to 18 hours a day. Their average flight time is 10 to 15 minutes, and some are as low as 3 minutes. Almost 80 percent of the flying time in agricultural spraying is spent in nonproductive flying, that is, turning around in the field and flying back and forth from the field to the home base. Only 20 percent of the time is actually spent spra.ying. So engine economy and reliability are key factors in this business. Typical engines range from 300 to 900 horsepower with the higher power engines being world war vintage radial engines. These are no producers of new radial engines in the United States today. The need for an engine in this horsepower class (between 400 and 900 horsepower) is illustrated by the Ag industry. 180 :1 1, :, Ii I Many operators are converting to turbine engines despite the higher initial cost. Experience is showing that the turboprop actually becomes profitable in about 2 1/2 years. The incremental cost may be. $75,000 to $100,000 for the conversion. The turboprop is proving to provide added power and payload across the field, and a quicker turn time. Those little 10 to 30 second increments that are saved because of the added power and added response of a variable pitch propeller tend to payoff in productivity of the aircraft. In conclusion, the numbers of aircraft and the growth rate of the industry over the next decade look very favorable. Constraints to the industry include noise: and fuel efficiency which are both subject to technology improvements. The trend in general aviation flying appears to be more toward instrument operations with the a"ircraft role becoming transportation oriented. Safe, reliable high horsepower engines are needed to allow higher power extraction for pressurization, air cond~tioning and other auxiliary systems as well as for special purpose aircraft such as used in the agricultural mission. 181 . , . 1 10.0 1.0 Billion $ 300 200 100 12 Number of aircraft 8 4 0 7l TRANSPORT AIRCRAFT Year Civil aircraft sales. Figure 1. - Growth record of civil aircraft sales. Piston ..- --- --- - -- - -- Turbine .-...- ...- ..:.--- -1-_____ " __ ---1- 75 80 Year Figure 2. - U. S. general aviation fleet (in thousands). 182 --- , ..- I 85 , , / " I Number of towers 1972 1973 1974 1975 1976 348 362 394 416 428 1982 459 10 Millions 40 30 Gei1eral aviation 20 Air carrier 10 Ir taxi o Fiscal years (* Indicates transitional Quarter) Figure 3. - Instrument operations at airports with FAA traffic control service. 2000 /;ISTOiI, en 1500 <>0 -l ./ ..... ~1 HP/LB ~ ./ OJ:: / '-" 1000 ---w ..... :;:: w z - 500 '-" z w I I 500 1000 1500 HORSEPOWER AT SEA LEVEL Figure 4. - Trends of engine weight with horsepower. 183 Millions , " f I. DBA (UOl max 90 80 50 40 o 18 16 14 12 10 8 6 1920 1000 FT ALTITUDL MAXIi1UM CONTINOUS pm/ER SE RULE IRFRAME NOISE 3000 6000 9000 12000 GROSS WEIGHT, LBS Figure 5. - Noise levels of small proileller driven vehicles. / 1930 1940 1950 Year 1.960 --7 - Re~eilrch goal o o 1970 1'180 Figure 6. - Trends in maximum lift-drag ratio of propeller drivrJn aircraft. 184 Figu re 7. - Photograph of Bellanca Skyrocket. Figure 8. - Photograph of Rutan AircrC' ft Company VarHze. \ \ 185 o o Single engine piston o o Twin engine piston o Twin engine turboprop 2000 0 o 0 iii 00 0 :::I 0 -- Os 0 0 E 00 :::I <08 SOC)) E giJ~o 0 ·x 0 E 1000 CE:J Cb lID§6 0 B 0 0 10 00 cfi° ° "CI 0 'C ° 0 ftJ o 0 ce ~o ~o ~ Q:?(§)o 0 >. ftJ 0- § eO ° () o ~ ° 0c53 0 ° o 0 0 I I I ---1 5 10 1.5 20 Nautical miles/gal Figure 9. - Payload carrying efficiency for typical general aviation aircraft.

The Rotary Combustion Engine: a Candidate for General Aviation

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