A Comparison of Inlet Valve Operating Strategies in a Single-Cylinder Spark-Ignition Engine

This experimental work was concerned with comparison of inlet valve actuation strategies in a thermodynamic single cylinder spark ignition research engine equipped with a mechanical fully variable valvetrain on both the inlet and exhaust. The research involved study of the effects of the valvetrain on combustion, fuel economy and emissions when used to achieve variable valve timing alone and when applied together with early inlet valve closing for so-called unthrottled operation. The effects of such early inlet valve closure were examined using either fully variable events or by simulating two-stage cam profile switching. While fully variable operation enabled the maximum fuel savings over the widest operating map, it was apparent that two-stage switching mechanisms can provide an attractive compromise in terms of cost versus CO 2 benefit on engines of moderate to large capacity. However, from speed-load maps obtained in the current study it would appear that a wide range of inlet valve durations would be necessary to obtain fuel savings sufficient to warrant a system any more sophisticated than current variable valve timing mechanisms in future aggressively downsized gasoline engines. © IMechE, 2009

Combining Unthrottled Operation with Internal EGR under Port and Central Direct Fuel Injection Conditions in a Single Cylinder SI Engine

This experimental work was concerned with the combination of internal EGR with an early inlet valve closure strategy for improved part-load fuel economy. The experiments were performed in a new spark-ignited thermodynamic single cylinder research engine, equipped with a mechanical fully variable valvetrain on both the inlet and exhaust. During unthrottled operation at constant engine speed and load, increasing the mass of trapped residual allowed increased valve duration and lift to be used. In turn, this enabled further small improvements in gas exchange efficiency, thermal efficiency and hence indicated fuel consumption. Such effects were quantified under both port and homogeneous central direct fuel injection conditions. Shrouding of the inlet ports as a potential method to increase in-cylinder gas velocities has also been considered. Copyright © 2009 SAE International

Fuel consumption of gasoline and diesel tractors when used with selected implements in West Tennessee

The rate of fuel consumption was measured for both gasoline and diesel tractors in size classes for use with two-, four-, and six-row implements. Tractors were operated at four different speeds with various sizes of the following implements: moldboard plow, tandem disc, planter, and cultivator. Fuel meters were designed and constructed to measure the amount of fuel consumed for gasoline and diesel tractors during field opera-tions. The fuel consumption was measured volumetrically by using systems of electrically-actuated solenoid valves to control the flow of fuel into and out of graduated cylinders. The moldboard plows in almost every instance required the most energy both per hour and per unit area with each tractor type. As a rule, the moldboard plow was followed in fuel consumption by the tandem disc, the cultivator, and the planter. As implement size increased fuel consumption per hour increased as did field capacities. An increase in operating speed resulted in an increase in fuel consumption per hour. However, the fuel consumed per unit area decreased as speed increased from 3.2 to 8.1 kilometers per hour (2.0 to 5.0 miles per hour). This suggests that certain implements with high field capacities plus high operating speeds may result in substantial energy savings

Analysis of combustion phenomena and knock mitigation techniques for high efficient spark ignition engines through experimental and simulation investigations

Different technologies are being utilized nowadays aiming to boost the fuel efficiency of Spark-Ignition (SI) engines. Two promising technologies which are used to improve the part load efficiency of SI engines are the utilization of downsizing in combination with turbocharging and cylinder deactivation. Both technologies allow a shift of load points towards higher loads and therefore towards more efficient zones of the engine map, while performance is being preserved or even enhanced despite the smaller displacement thanks to high boost levels. However, utilization of both technologies will increase the risk of knock dramatically. Therefore, the abovementioned systems can be coupled with other technologies such as gasoline direct injection, Miller cycle and water injection to mitigate knock at higher load operating conditions. Therefore, the aim of the current work is to investigate, through experimental and numerical analysis, the potential benefits of different knock mitigation techniques and to develop reliable and predictive simulation models aiming to detect root cause of cyclic variations and knock phenomena in downsized turbocharged SI engines. After a brief introduction in Chapter 1, three different typical European downsized turbocharged SI engines have been introduced in Chapter 2, which were used for both experimental and simulation investigations, named as Engine A, which is downsized and turbocharged, Port Fuel Injection (PFI) with fixed valve lift and represents the baseline; Engine B, represents an upgraded version of Engine A, featuring Variable Valve Actuation (VVA), and Engine C which is a direct injection and further downsized engine. Engine B, equipped with MultiAir VVA system, was utilized to evaluate the possible benefits of cylinder deactivation in terms of fuel economy at part load condition, which is discussed in Chapter 3. Since the MultiAir VVA system does not allow exhaust valve deactivation, an innovative strategy was developed, exploiting internal Exhaust Gas Recirculation (iEGR) in the inactive cylinders in order to minimize their pumping losses. However, at higher load operating condition, risk of knock occurrence limits the performance of the engine. Therefore, the possible benefits of different knock mitigation techniques such as Miller Cycle and water injection in terms of fuel consumption were discussed in Chapter 4. Potential benefits of Miller cycle in terms of knock mitigation are evaluated experimentally using Engine B, as shown in Chapter 4.2. After a preliminary investigation, the superior knock mitigation effect of Late Intake Valve Closure (LIVC) with respect to Early Intake Valve Closure (EIVC) strategy was confirmed; therefore, the study was mainly focused on the latter system. It was found out that utilization of LIVC leads up to 20% improvement in the engine indicated fuel conversion efficiency. Afterwards, Engine C, a gasoline direct injection engine, has been utilized in order to understand the potential benefits of water injection for knock mitigation technology coupled with the Miller Cycle, which is discussed in Chapter 4.3. Thanks to water injection potential for knock mitigation, the compression ratio could be increased from 10 to 13, which leads to an impressive efficiency improvement of 4.5%. However, utilization of various advanced knock mitigation techniques in the development of SI engines make the system more complex, which invokes the necessity to develop reliable models to predict knock and to find the optimized configuration of modern high-performance, downsized and turbocharged SI engines. Considering that knock is strictly related to Cycle-to-Cycle Variations (CCV) of in-cylinder pressure, CCV prediction is an important step to predict the risk of abnormal combustion on a cycle by cycle basis. Consequently, in Chapter 5, a procedure has been introduced aiming to predict the mean in-cylinder pressure and to mimic CCV at different operating conditions. First, a 0D turbulent combustion model has been calibrated based on the experimental data including various technologies used for knock mitigation which can impact significantly on the combustion process, such as Long Route EGR and water injection. Afterwards, suitable perturbations are adapted to the mean cycle aiming to mimic CCV. Finally, the model has been coupled with a 0D knock model aiming to predict knock limited spark advance at different operating conditions. Finally, in order to provide a further contribution towards the prediction of CCV, 3D-CFD Large Eddy Simulation (LES) has been carried out in order to better understand the root cause of CCV, presented in Chapter 6. Such analysis could be used to extract the physical perturbation from the 3D-CFD and to use it as an input for the 0D combustion model to predict CCV. The operating condition studied in this work is at 2500 rpm, 16 bar brake mean effective pressure (bmep) and stoichiometric condition. Based on the analysis conducted using LES, it was found out that the variability in combustion can be mainly attributed to both the direction of the velocity flow-field and its magnitude in the region around the spark plug. Furthermore, the effect of velocity field and equivalence ratio on the combustion has been decoupled, confirming that the former has the dominant effect while the latter has minor impact on combustion variability. In conclusion, simulation models using 0D and 3D-CFD tools when calibrated properly based on experimental measurements can be used to support the design and the development of innovative downsized turbocharged SI engines considering the effects of CCV and knock on engine performance parameters

Thermal efficiency and emission analysis of advanced thermodynamic strategies in a multi-cylinder diesel engine utilizing valve-train flexibility

Stringent emission regulations and a growing demand for fossil fuel drive the development of new technologies for internal combustion engines. Diesel engines are thermally efficient but require complex aftertreatment systems to reduce tailpipe emissions of unburned hydrocarbons (UHC), particulate matter (PM), and nitrogen oxides (NOx). These challenges require research into advanced thermodynamic strategies to improve thermal efficiency, control emission formation and manage exhaust temperature for downstream aftertreatment. The optimal performance for different on-road conditions is analyzed using a fully flexible valve-train on a modern diesel engine. The experimental investigation focuses on thermal management during idling and high-way cruise conditions. In addition, simulation are used to explore the fuel efficiency of Miller cycling at elevated geometric compression ratios. ^ Thermal management of diesel engine aftertreatment is a significant challenge, particularly during cold start and extended idle operation. For instance, to be effective, NOx-mitigating selective catalytic reduction (SCR) systems require bed and gas inlet temperatures of at least 200°C, and diesel oxidation catalysts coupled with upstream fuel injection require inlet temperatures of at least 300°C in order to raise diesel particulate filter inlet temperatures to at least 500°C for active regeneration. However, during peak engine efficiency idle operation, the exhaust temperatures only reach 120 and 200°C for unloaded (800 rpm/ 0.26 bar BMEP) and loaded (800 rpm/ 2.5 bar BMEP) idle, respectively, for a typical modern-day diesel engine. For this and other engines like it, late injections or throttling (for instance via an over-closed variable geometry turbocharger) can be used to increase exhaust temperatures above 200°C (unloaded idle) and 300°C (loaded idle), but result in fuel consumption increases in excess of 100% and 67%, respectively. Fortunately, and as this thesis describes, cylinder deactivation can be used to increase exhaust temperatures above 300°C at the loaded idle condition without increasing fuel consumption. Further, at the unloaded idle condition, the combination of cylinder deactivation and flexible valve actuation on the activated cylinders allows 200°C exhaust temperatures without a fuel consumption penalty. At both operating conditions the primary benefits are realized by reducing the air flow through the engine, directly resulting in higher exhaust temperatures; and as good, or better, open cycle efficiencies compared with conventional 6 cylinder operation. In all cases, comparisons are made with strict limits on engine out NOx, unburned hydrocarbons, and particulate matter emissions. ^ Internal exhaust gas recirculation (iEGR), late intake valve closure (LIVC) and cylinder deactivation (CDA) were experimentally investigated as methods for fuel economy and thermal management at 1200 RPM and 7.58 bar brake mean effective pressure (BMEP), which corresponds to the highway cruise condition for over the road trucks. These strategies were compared with conventional operation on the basis of optimized fuel consumption, exhaust temperature, and exhaust power at three NOx targets. Physical constraints and emission limits were set to ensure realistic engine operation and emission regulations. The results show that conventional valve profiles lead to the best fuel economy, but iEGR, LIVC and CDA increase achievable exhaust temperature by 57-216 °C. iEGR increases exhaust temperatures by eliminating the heat rejection that occurs when using external EGR. Both LIVC and CDA increase combustion temperature by reducing the air to fuel ratio. ^ Advanced thermodynamic strategies such as the Miller cycle and Atkinson cycles have been realized on production spark ignition engine through variable valve timing. However, fewer efforts have been directed to compression ignition engines. Increases in geometric compression ratio typically lead to increased thermal efficiency, but the application is constrained by physical limits including peak cylinder pressure and turbine inlet temperature. An experimentally validated model was used to obtain the trade-off; between fuel economy and NOx emissions in order to thoroughly investigate Miller cycling at elevated geometric compression ratio. The results demonstrate the expected improvement in thermal efficiency, however, as expected, the maximum in-cylinder pressure and temperature violate the physical constraints at elevated power conditions. These challenges can be addressed through the use of Miller cycling via a reduced effective compression ratio through the modulation of intake valve closure. Miller cycling enables the engine operation with elevated geometric compression ratio at maximum power condition and further improves fuel economy by advancing combustion. The results present a 5% fuel economy improvement at operating conditions without EGR and equivalent fuel consumption when EGR is incorporated. Brake thermal efficiency (BTE) is improved by 0.1%-2% using Miller cycle at elevated GCR. Although EGR was able to achieve very low NOx emissions, fuel economy was sacrificed at medium load condition. Moreover peak cylinder pressure (PCP) and turbine inlet temperature (TIT) exceeded the upper limits at maximum power condition using EGR with elevated geometric compression ratio

Effects of Temperature on the Performance of a Small Internal Combustion Engine at Altitude

The effects of atmospheric pressure and temperature variations on the performance of small internal combustion (IC) engines operating at altitudes significantly above sea level are not widely documented. Using an altitude chamber and fuel-injected twostroke engine, data were collected while varying air temperature along with pressure. The peak engine power was 4.1 kW at roughly sea level standard conditions and dropped to 3.5 kW at the standard conditions for an altitude of 1.5 km. At a combination of pressure and temperature corresponding to an altitude of 3 km, peak power fell further to 2.5 kW. The combined effects of standard atmospheric conditions showed pressure dominated temperature and resulted in around a 3.5% loss of power and brake mean effective pressure (BMEP) along with a 3% increase in brake specific fuel consumption (BSFC) per 300 m increase in altitude

Utilization Of Variable Valve Actuation To Improve Fuel Efficiency And Aftertreatment Thermal Management In Diesel Engines

Fuel consumption in heavy-duty vehicles is expected to double by the year 2050 [1]. The majority of heavy duty vehicles incorporate diesel engines which emit air pollutants including particulate matter (PM), unburnt hydrocarbons (uHC) and oxides of nitrogen (NOx). Increasing demand for heavy duty transportation coupled with strict emission regulations by the Environmental Protection Agency (EPA) and California Air Regulations Board (CARB) to improve air quality drive innovation of advanced engines and auxiliary systems. Complex exhaust aftertreatment (AFT) systems are required to meet stringent tailpipe-out emission regulations. The effectiveness of AFT systems, affected by emission conversion efficiency, is limited when turbine outlet temperatures (TOTs) are low (usually used to reduce the fuel consumption by 5 to 30% depending on the engine load, increase the rate of warm-up of AFT, maintain higher AFT temperatures, and achieve active diesel particulate filter regeneration without requiring HC dosing of the diesel oxidation catalyst. At cruise operating condition (1200 rpm/300 ft-lbs), Late IVC (LIVC) strategy does not show any fuel economy penalty when compared to conventional operation of the valves, but shows a TOT increase of about 150-200◦C, thereby enabling warmer AFT temperatures. This dissertation also introduces several novel engine breathing modes, viz. fired/non-fired reverse breathing and intake/exhaust re-breathing. Reverse breathing is a novel method where exhaust gases are recirculated, as needed, from exhaust manifold to intake manifold via one or more cylinders. Re-breathing is an innovative method, where the gas exchange takes place only in either the intake or exhaust manifold for a certain number of cylinders. These strategies provide in-cylinder oxygen dilution and reduction in airflow leading to lower pumping work at low-load engine operation. Approximately 40% of typical heavy-duty vehicle operation occurs at loaded curb idle, during which the conventional diesel engines are unable to maintain sufficient AFT component temperatures while retaining fuel economy. Fuel economy and thermal management at loaded curb condition can be improved via reverse breathing due to reduced airflow. Several strategies for implementation of reverse breathing are described in detail and compared to CDA and internal EGR operation. Experimental data demonstrates 26% fuel consumption savings, when compared to conventional stay-warm operation; 60◦C improvement in TOT, and 28% reduction in exhaust flow compared to conventional best fuel consumption operation at the curb idle condition (800RPM, 1.3 bar BMEP). Similarly, intake rebreathing in three of the six cylinders yields 50◦C improvement in TOT and 20% reduction in exhaust flow while maintaining NOx levels without using EGR. The incorporation of non-fired reverse breathing, in order to efficiently maintain desired AFT temperatures during curb idle conditions, is experimentally demonstrated to result in fuel savings of 2% over the HDFTP drive-cycle relative to conventional operation

English. Навчальний посібник з англійської мови для студентів І-ІІ курсів спеціальності «Автомобілі і автомобільне господарство»

Part I… Lesson 1. Essential parts of an automobile… 5-- Unit 2. Types of Waves…8 -- Unit 3. Speed of Waves… 10-- Unit 4. Interactions of Waves…13-- Unit 5. Electromagnetic Waves…16-- Unit 6. Type of Waves…19-- Part II…22-- Unit 1. Infrared Rays… 22-- Unit 2. Visible Light…25-- Unit 3. Wave or Particle?... 29-- Unit 4. Reflection of Light…31-- Unit 5. Reflection and Mirrors…34-- Unit 6. Refraction of Light…37-- Unit 7. Optical Instruments…40-- Unit 8. Lasers…43-- Unit 9. Fiber Optics… 47-- Part III… 52-- Unit 1. A Halogen Lamp…52-- Unit 2. LED Lamp…54-- Unit 3. Electroluminescent Wire… 57-- Unit 4. Black Light… 59-- Unit 5. Compact Fluorescent Lamp (CFL)… 62-- Unit 6. Plasma Lamps. …65-- Unit 7. Architectural Lighting Design…68-- Part IV…70-- Additional reading… 70-

Interactions between charge conditioning, knock and spark-ignition engine architecture

There are currently many factors motivating car manufacturers to reduce the tailpipe CO2 emissions from their products. One of the major routes to achieving reduced CO2 emissions in spark-ignition 4-stroke engines is to ‘downsize’ the swept volume which, among other advantages, reduces the proportion of fuel energy expended on pumping losses. The full-load performance deficit caused by reducing the swept volume of the engine is normally recovered by pressure charging. One of the limits to pressure charging is combustion knock, which is the unintended autoignition of the last portion of gas to burn in the combustion chamber after combustion has been initiated. This thesis presents results from investigations into a number of methods for suppressing knock, including (1) tests where the density of the intake air is closely controlled and the effect of charge air temperature is isolated, (2) where the latent heat of vaporization of a fuel is used to reduce the outlet temperature of a supercharger, and (3) where the engine architecture is configured to minimize exhaust gas residual carryover to the benefit of stronger knock resistance. Extensive comparison of this resulting engine architecture is made with published data on other strategies to reduce the effect of the knock limit on engine performance and efficiency. Several such strategies, including cooled EGR, were then investigated to see how much further engine efficiency (in terms of brake specific fuel consumption) could be improved if they are adopted on an engine architecture which has already been configured with best knock limit performance in mind. Within the limits tested, it was found that if the charge air density is fixed then the relationship between knock-limited spark advance and air temperature is linear. This methodology has not been found in the literature and is believed to be unique, with important ramifications for the design of future spark-ignition engine charging systems. It was also found that through a combination of an optimized direct-injection combustion system, an exhaust manifold integrated into the cylinder head, and a 3-cylinder configuration, an engine with extremely high full-load thermal efficiency can be created. This is because these characteristics are all synergistic. Against the baseline of such an engine, other technologies such as excess air operation and the use of cooled EGR are shown to offer little improvement. When operating a pressure-charged engine on alcohol fuel, it was found that there exists a maximum proportion of fuel that can be introduced before the supercharger beyond which there is no benefit to charge temperature reduction by introducing more. Strategies for reducing the amount of time when such a system operates were developed in order to minimize difficulties in applying such a strategy to a practical road vehicle. Finally, a new strategy for beneficially employing the latent heat of vaporization of the fuel in engines employing cooled EGR by injecting a proportion of the fuel charge directly into the EGR gas is proposed. This novel approach arose from the findings of the research into pre-supercharger fuel introduction and cooled EGR

Performance and emissions of a medium-speed engine driven with sustainable options of liquid fuels

Energy production and transport are major global contributors of greenhouse gas emissions. Both sectors should reduce their use of fossil energy sources. Pollutant emissions must also be reduced without jeopardizing energy efficiency, reliability, and profitability. The internal combustion engine will dominate in marine and power plant applications for a long time because it offers high energy density, efficiency, durability, and the ability to respond rapidly to load changes. Ever-tightening emissions legislation encourages development of new solutions for engine-driven power. One example is exploring the use of alternative fuels in large engines. Low-carbon liquid fuels with high energy density are ideal for applications working far from any infrastructure. This study evaluated how three liquid fuel alternatives perform in a medium-speed engine. One new fuel was a circular economy-based marine gas oil (MGO). The second novelty was a blend of renewable naphtha and low-sulfur light fuel oil (LFO). Neat LFO served as the baseline fuel. The study started with thorough fuel analyses, including the fuels’ ignition properties. Then, a medium-speed engine was driven with each fuel by using similar engine settings and without exhaust aftertreatment. The results indicate that the thermal efficiencies were almost equal for all fuels at all studied loads. No notable differences were observed in the heat release curves. The naphtha/LFO blend produced slightly increased HC emissions at low loads but showed the lowest HC at full load. NOx emissions were very similar with all fuels. MGO and naphtha/LFO blend usually emitted fewer ultrafine exhaust particles than LFO. Methane and nitrous oxide emissions were always very low. Overall, both novel fuels could be adopted for medium-speed engines.fi=vertaisarvioitu|en=peerReviewed