An overview on engine development projects for potential use of ceramics is reported. A major ceramics materials technology effort is described to meet anticipated engine system requirements in terms of the automotive application, some of the more pressing technology needs, and some indications of how to conduct this technology program with industry-engine development projects focus on both gas turbine and Stirling engines

Blankenship, C. P.

Schulz, R. B.

English

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OPPORTUN IT I FS FOR CERAMICS IN THE ER DANA SA 	 1
CONTINUOUS COMBUSTION PROPULSION SYSTEMS PROGRAM
	
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1
by Charles P. Blankership and Reber' B Schulz
Lewis Reseo.r ch Center
Cleveland, Ohi , 44135
TECHNICAL PAPER fc b- pr esented at be
Workshop n Cer-tin,.•
	 r Energy C, nver• si( n Systems
sponsc,red by the Ene r gy Rose,,.-ch a.nd Devel, pmer:° Admrn:stra.tron
Oi la.ndo, F1	 ido- Jdnuz, • v 24-27, 1977
I!
i .
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OPPORTUNITIES FOR CERAMICS IN THE ERDA/NASA
CONTINUOUS COMBUSTION PROPULSION SYSTEMS PROGRAM
Charle y P. Blankenship, NASA-Lewis Research Center
Robert B. Schulz, EFDA-Transportation Energy Conservation Division
4
3.
INTRODUCTION
rn
W	 The ERDA/NASA Continuous Combustion Highv,ay Vehicles Program is directed tc..ard
reduced fuel consumption in highway vehicles. Both the gas turbine and Stirlinc, engines
are of immediate interest because of their potential improved fuel econar,iy as co.;ared
to current automotive pov.-eralants. Project management of this ERDA-funded prc;-a- has
been assigned to the NASA-Le,ois Research Ce n ter. The prime objc ,tive of this program
is to help industry establish the technological position necessa ry to have the option
of gas turbine and/or Stirling powerplant production. Specific program goals are di-
rected at improved fuel econcr/, low emissions, multifuel capability, and narketability.
For example, a 20-30 percent gain in fuel economy i targeted for an "improved engine"
option by 1982 -83. For the late 1980's, a 50-60 percent gain in fuel economy . is targeted
for "advanced engine" syste°-s.
High temperature cera • ic • aterials are expected to receive r;ajor emphasis in devel-
oping both improved and advanced gas turbine and Stir.-ling engines in this program. The
use of ceramics provides the opportunity to achieve higher operating te7peratures rhich
contributes directly to i-prci's^g the thermodyna-.ic efficiency of these engires, and
thus their fuel economy. Also, the use of ceramics instead of superalloys usually
e7ployed in these applicatio-,s offers the potential of reduced material costs ark re-
duced demand for critical alloy -.etals such as chromium, nickel, and cobalt. Potential
high temperature structural cera ics such as silicon nitride and silicon carbide are
derived from relatively aburca-.t and low cost elements. 	 In addition to higher e:.erating
te-peratures, greater efficie-_ies are expected in Angine components through i -^rc:ed
designs and operating characte-istics.
This paper presents an overview of the program scope with emphasis on the a- ,nine
development projects and key ,;:ortunities for potential use of ceramics. A
ceramics materials technolc;i e^`ort is also described % .,hick arilI be cond,jcte^	 -eet
anticipated engine s /ste ­ 	 - ents. We conclude with con -ents relatin g !,^ ; - e unique
nature of Chi •, progra^• in !e of the automotive application, cone of the mo-e pressing
technology needs, and sof-e i^;'cations of how we p4an to conduitt this technolc:j ;rogram
with industry.
; SINE DEVELOPMENT PROJECTS
Engine development projects will focus on both qas turbine and Stirling e-sires.
Both of these engines are co n sidered to be promising fuel -efficient enqines teat could
be rrass -produced and sold as el!ernatives to the conventional internal co-bus!ion e-gine
for introduction in automot:'es in the 1985-1590 time fraTe. The engine dere'-r-ent
projects are to be conducte'. c-f • '.e industry thre;;;`) govern-ent- f u n ded cont-rtts.
STAR CAT. 27
90DUCIBILITY OF 'l'i'ly.
r :l err, PAW E IS P(x)R
4
Emphasis in these'prbjects will be to assist the automotive industry in achieving the
technology base needd for a production option of alternative automotive propulsion
systems. Efforts for both "improved engines" (for possible use in the mid-1980's) and
"advanced engines" (for potential use in the 1990'x) are planned as outlined in the
following sections.	 Improved engines are classed as existing development engines that
would be upgraded without significantly changing their principal design features. Ad-
vanced engines would evolve from new engine design concepts.
Improved engine development projects. This part of the program will emphasize im-
provements in currentdevelop.--ent engines or new engines to meet the near term, 1982-83
goal of a 20-30 percent Main in fuel economy. Existing and near-term technology ;could
be used to achieve this and other progra , goals. Ceramics are expected to receive ,,ajor
emphasis in improving the performance of these engines, but ceramic co ponents are likely
to be used on a selective basis. One approach %•could be to introduce ceramics into the
engine on a component-by-component basis and thereby provide for incremental iriprove-ments
in engine performance.
Specific opportunities for ceramics in this type of program will be illustrated
using as an example the Improved Heavy Duty Gas Turbine Engine Program. This program
is being conducted by Detroit Diesel Ailision (ODA) under NASA contra-c (NAS3-20064) and
is part of the ERDA/NASA Contin,;ous Comtustion Propulsion Systems Program. The goal of
the heavy duty engine progra^i is to advance automotive gas turbine systems technology
and to significantly improve the specific fuel consumption of DDA's 404/505 industrial
gas turbine development engine from its current level of 0.45. Thjs engine is contem-
plated for highr.ay truck and bus applications. A step-type program is planned which
consists of advancing the turbine inlet te:perature from the current level of 18350F to
19000 F, to 20700F, to 220'50 F, and possibly to 25000 F. Each step of increasing te•rpera-
ture involves introduction of addit; -al __ramie components in the hot -ction of the
engine. A ceramic regarierator disk, a ceramic gasifier nozzle, and a cera-.ic gasifier
tip shroud :.ould be rc:,uired to achie:_- the 1900 OF increment follo.:ed b/ a ceramic
co.,b..stor plenum and ceramic ;asifier rotor blades to achieve the 2070O F operating
temperature. At the highest temperature, -lost components in the hot section -.would be
cera-iic.
	 In the current study phase of this project, - the potential benefits of in-
creasing cycle temperature anJ adding sera^ic components are being evaluated in terms
of life-cycle-costs.
	 These res.:lts %. ill to used to help guide subsequent phases of the
pro^,ram which will involve ce-a-,ic co-;srent design, fabrication, and testing. 	 Both
engine and vehicle demonstrations are to he made at each r^ajor step of the improved
engine development project.
Other governr,ent
- supporte. projects are planned; to develop improved gas turbine
engines for automotive use. T--!se prc?-a~s will be conducted by the auto--*tive industry
	 i
through contracts with NASA. :era-ics are expected to be utilized for selected hot
section components. Like tie p revious er.a-,ple given, these improved engine projects
will contain significant ef f orts in ce-+, ic technology development covering ^ater•ial
i•:.-,ve-ents, charnct -iz.a*_;o 
	 fabrication, and engine testing.
e
	
	 For the Stirling engine, -troduct : on of ceramic co-^ponents is planned to develop
an i^proved engine by 1982. 4owever, t^e introduc;ion of ceramics in this engine is
expected to be limited to t-e z-e- s eater to minimize the hi g hef risk asscC ated with
this engine development pro;-a-. Sot"  rotary regenerator and fired recuperator concepts
,J 1 1 1^e cons idered.
Advanced engine develor--e-t projects.
	
In the advanced enqine develop-ent progra-),
e-phases Is ^xpecte to 5° o.t_e: c ^^t advanced 'engine deign concepts a^d cera^rie
mater i z's. While sore preii -ar, - :catual engine design work will be u^dertaken by
NASA, the rnajor effort wi : 	r- __ tra.t pd to industry. This latter effort is expected
to start in rY78. Se_ver:a' ,-.-?:. Qu irts are planned	 to de -`-s the
advanced propulsion ;ys*e- s	 technology r^., _c_e^ts, ? s ecs 'nitiai system
definition proj e cts will .P - 
-4^._.	 -?r;! a orogra r a:
	 !	 s on ^o'" •	 "13. At
2
	
	
RFI)RODUCIBILITY or THE
i,iMMNAL PAGE IS POOR
" that time, the governmer*, with inp-it from industry, would determine merits of continuing
the support of the advanced engine development program with a view toward achieving an
early 1990 production possibility. Key factors in this decision would inc ude fuel
economy projections, potential marketability of the advanced engines, and projected
national needs.
The "advanced engines" are expected to operate at higher temperatures and require
more ceramic components than envisioned in the "improved engines." For advanced gas
turbine engines, all hot section components are likely to be ceramic. A ceramic turbine
rotor, essential for an all-ceramic turbine, is judged to be the most difficult technol-
ogy development.
CERAMIC MATERIALS TECHNOLOGY PROJECT
The ceramics materials technology project is expected to provide technology for both
the improved and advanced engine p rograms with emphasis on the latter. A broad-based
effort is planned to include in-death characterization of various ceramic materials,
development of improved ceramic 7,aterials and processes as well as component design,
fabrication, and testing. A brief outline of the planned efforts covering these three
principal areas is provided in the following sections. Areas of technology emphasis
are also noted. The major portion of this activity will be accomplished by industry
through government-funded contract programs.
Characterization of ceramic materials. This technology area coverts the in-depth
characterization of mechanical ana physical properties of current and advanced structural
ceramics that have potential for engine applications. Maintaining a design data-base on
candidate ceramic materials is vie,red as a key area in this part of the program to
provide input to the engine design activities.
	
In addition, the durability of ceramics
in terms of the effects of long-ti-.e engine exposure on mechanical properties and
stability will be evaluated. 	 Ot`:er efforts will include non-destructive evaluation,
fracture mechanics, life-prediction methodology, and reliability analyses.
Improved ceramic materials. Efforts in this area will focus on developing improved
ceramic materials to better -eet future automotive requirements. For example, higher-
density reaction-sintered silicon nitride is desirable for both improved strength and
oxidation resistance. A projec t. to achieve this would include optimization of the
silicon powder particle size and distribution, refinement of the nolding process, and
improvement of the understanding and control of the nitradation step. Similar tech-
nology efforts can easily be identi=ied for other candidate materials such as silicon
carbide and the oxide ceramics. laii1e improved material properties will be emphasized,
the applicability and economic viability of the related fabrication technology for the
improved ceramic material will receive appropriate attention. 	 Fabrication processes
associated with improved materials -1st have potehtial for low cost and high volute
Production capability.	 %
Component design, f afr' cat'^-, a^d testing. Technology progra-s : n t h is category
reflect the need to obtain a str;-, tecnnology base in ceramic component performance.
Efforts in this area may not be related to s pecific engine designs, but they will
address key issues such as veri g 'ca!ion of ceramic design concepts and component reli-
ability' under operating conditic- , . Riq testing of components will be used as appropriate.
Cera-iic manufacturing technolog y ce, p !oo--ent will also be included to Letter Tatch new
co,rponent designs with fahrical:;-	 c esses.
	
Ceramic component -a nu`acttire at reason-
able cost and high reliability will w ave co be demonstrated in order for the industry
to have a viable engine optio-. '-ie development of low =cost manufacturing technology
as well as the component de-ionstrc_ " ,i technoiogy will be included in this part of
the program.
3
	
	 REPRODUCIBILITY OF THE
f-AR?MNAJ, VA01. IS POOR
1
-4CLUDING REMARKS
This paper Is intended to Le in overview of the ERDA/NASA Program which is in the
early phase of planning and i • ;ierentation. Obviously, there will oe changes in specific
details as the program progresies and as technology needs are better defined. The strong
technical reasons for using ce ,a-ics ; n the program are probably oblicus to this audience.
Also, current ceramic naterials t-at are likely candidates for the engine components
noted are well known to this Sr,,;, For these reasons, we have not attempted to relate
the merits of any one candidatt ceramic material nor to provide a review of the status
of ceramics for enqine applicat ­.-s.	 (A list of references is provided for those %-. ,ant-
R	 inq aJJitional background).
Several technology pro;ra
	 -a ye provided much of the impet.:s and a degree of
optimism that ceramics can nc.: ce considered as viable structural -aterials in high
Perforr-ance applications such a. alvanced automotive engines. The -ost notable include
the ARPA/Ford Brittle Material ;e;'; D roaram and the recently-initiated :ARPA/AiResearch
Cera-iic Engine De,-:onstration % --a-. 3oth of these programs f a,e :.el) defined objec-
tives. And they are Jistinctil + :;=ferent in scope when compared to the ERDA/NASA
Program. The ARPA programs .+iil culminate in 50 to 200 hour engine tests to de,,onstrate
the feasibility of using cera-ii: cz-;onents in turbine engines. Hc,.ever, the ERDA/NASA
Program will concentrate on tie tec'-,nology needed to ultimately use reliable, cost-
effective ceramic components in
	
engines for 3000 to 4300 sours of engine
operation that includes about ^:,:;; engine start-ups and shut-downs. These 6ften
conflicting require,ients of gc:d e-..urance, high reliability, and lo.o cost present a
very formidable challenge in deie;sping the technology for ceramic use in aut6r•.otive
applications.
One of the first steps 	 ., _-.DA/'.ASA ceramic technology prc;-am vill be to eval-
uate the effects of long-ter- :,c.'c e,:posure (3000-4000 hrs.) to si-.,,lated engine
elv : -on •-,ent on :mechanical arc;c-:'., a-J structural stability of candidate ceramic
-laterials.	 We want to identi , ; ,,.2--131 problems associated with the long-life, cyclic
requirements of an automobile e-;'-e early in the technology program. For example, the
loss in strength (about 30 perce-:	 --it pressed silicon-nitride, a candidate
structural ceramic, after ex p ;;_-	 c'r at 2000O F for about 400 ours :.as only
identified recently.
	
Identi = '::.	 ;otential problems of this t, , -a is needed early
to properly direct the acti:i:	 --e undertaken i.n the improved :era-iic materials
part of the technology progra-.
Design methodology for st-_c:_-a! ceramics is ang.ther key area of concern to be
addressed in both the engine __:e'_ -s-t and supporting technolcgy _ :^;-a-ns. The
pro5abili , tic design approaci e.: ,e., i^. the ARPA/Ford program. pro p r°s a :ell-founded
technical base. Our imnedia:e -ee: .-en is to assess these conce p ts :-rough extended
rig and enqine tests of co-p:-e-:a a-t Ceternine their applicability for the autoTotive-
type application.
^elia!)iIity of cera'-:ic'> 9':	 - - -.:;t-effectiveness in the auto motive application
will be the keys to their Success.	 current state-of-technolog y rakes it difficult
to realistically assess eit l-e^	 --eSe `actors.	 Ceramic engine ` ce-,-.onents, except
perhaps rotary heat exchan gers, -a:e -;t been manufactured or teste3 i n quantities
sufficient to assess either -e a	 or cost.	 Early in the nr . ^-a-, r;e expect to be
in 9 " ,;itiun to f ocus p ! r *.	 ' e.".'cep in initiating this )'..:_-^_nt. 	 This '-ay
be	 partly th ► u ., •,-	 e-; -e dc^elopment projects a^d partly through
the ceramics technology pro.e:-:	 - _._tinual update of the reJiat^ ; Iity and cost
factors will have to be ^ai^:a t'
	
-elp provide proper focus and program direction.
Finally, we have not atty : •e !	 -ike_ a clear distinction ir. • ~e b7' ! ^da r '95 ^-!^:-±en
the end ^`± dev° I n ,, °nt o r^'^:._ a', ,-. [Ir '-7ic materials t p c , Wo j/ 	 G
na ter ials evaluation wiII gt 
-^_3	 x s -a r t of both. T'-ere v :• ' ~- 	 10
dupl ication of e f "ort.	 ,	 - _ : 7 , ^al, but warra ^t4:, 	:er t7 C:-G! -7 •^-e
4
	
	
RF.PRODUCIRILI'1'Y OF T11F
. 'M !XI. PAGE IS P(X)!t
performance of candidate cera l iC r:aterials. our intent to assist the entire autorotive
industry further cinplicates this problem since there will be several companies partici-
,,sting in the automotive ccntirucus combustion engine technology program. Identical
ceramic materials are likely tc be selected by two or more companies for the sa-e co po-
nent but with differing desk ,-s. Also, manufacturing technology efforts and design data
are likely to be similar, 	 ',r, _onsidering a different aspect, the sa:i.e tour ca•,Jidate
-iaterials might be selected f or evaluation by several companies. Obviously, the solution
to minimizing duplication of effort in this type of program is certainly not straight-
forward. But one part of tme ;,otential duplication that can most easily be avoided is the
o-.taining of engineering des _^ data, one or tore independent laboratories could be
4!
.7:ed to generate these data 'rr the entire industry for all candidate cera ,g ic3. So
..e are evaluating this aa pr c.s: and others to provide a reasonably-balanced pr(,;ra-I
,.itIn industry. Thus, a major cart of our job in managing this program will be to
ini-,ize duplication while at tre same time truly assisting the industry in achieving
t~e technology required to haze an option of advanced engine production to enha~;e our
national energy posture.
REFERENCES
1, "Highway Vehicle Systems :cntractors Coordination Meeting" (Tenth Summary Ra,:;rt),
ERDA-76-136, May 1976.
2, "Ceramic Gas Turbine Engine De onstration Progra:i" (Interim Report No. 2), AiBesearch
Report No. 76-212188, Septe-:er 1976,
i
3. ~-.Lean, A. F., and Baker,	 ?,; "Brittle Materials Design High Te7perature Sas
,.rbine," AWiRC CTR 76-31, --:J^er 1976.
4,	 2irke, J. J,, et. al, =J	 ._ramics for High Perfor-^ance Applications,"
y -ookhill Publishing Co.,
5	 „'


Opportunities for ceramics in the ERDA/NASA continuous combustion propulsion systems program

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