Spark Ignition Gasoline Engine Research Articles

The performance of a spark ignition gasoline engine with hydrogen addition under low-load conditions

With continuously increasing populations and industrialization, more and more green consumers and stringent emission regulations promote low-carbon or zero-carbon alternative fuels in transportation sector. Hydrogen is considered carbon-free when produced using environmentally friendly methods, and could achieve zero carbon emission in the internal combustion engines. This study comprehensively explores the influences of the hydrogen addition on the performance of the gasoline spark ignition (SI) engine operated at low-load conditions. The experimental results showed that the abnormal combustion cycles of the test gasoline engine are greatly reduced with hydrogen enrichment. In addition, the coefficient of variation (COV) of the indicated mean effective pressure (IMEP) of the gasoline engine is 2.66 % under the 1500 rpm and 0.2 Mpa (brake mean effective pressure: BMEP) condition, while the COV of IMEP of the engine fuelled with gasoline and hydrogen is 2.34 % at the same condition. Furthermore, the knocking intensity of the gasoline engine is strengthened by adding hydrogen because the averaged maximum pressure rise rate (MPRR) of the gasoline SI engine is slightly increased. Besides, the indicated thermal efficiency (ITE) of the gasoline engine is increased 0.9 % and its maximum increase rate of the ITE is 4.27 % with hydrogen addition at the 1300 rpm and 0.2 MPa condition. Last, unburned HC, CO, and CO2 of the gasoline engine are reduced while NOx emissions increase with adding hydrogen due to high combustion temperature.

Impacts of fuelling methods on knock-limited combustion and emissions of a dedicated hybrid spark-ignition engine

This study investigates the impact of various fuelling methods on knock-limited combustion efficiency and emissions in a high compression ratio, turbocharged spark-ignition gasoline engine designed for hybrid applications. Different injection strategies, including port fuel injection (PFI), direct injection (DI), two-stage DI, PFI with late DI, and PFI with in-cylinder targeted fuel injection (TFI), were evaluated. TFI, a novel method where fuel is injected towards knock-prone regions based on knock spatial distribution, was seen capable of advancing the knock-limited spark advance (KLSA) by up to 3.75°, and hence reducing fuel consumption by 18.78 g/kWh, demonstrating significant knock suppression. Furthermore, trade-off characteristics between fuel consumption and particulate emissions resulting from injection strategies were exhibited from the measured data. DI produces the optimal fuel consumption and the worst particulate emissions, while PFI shows the opposite. Importantly, TFI improves the trade-off, reducing fuel consumption and emissions simultaneously. The refined TFI achieved a 96.6 % reduction in particulate emissions compared to DI, matching PFI levels while improving engine thermal efficiency. These different combustion characteristics are attributed to the localized fuel–air mixing and charge cooling affected by injection strategies.

Experimental investigation for enhancing the performance of hydrogen direct injection compared to gasoline in spark ignition engine through valve timings and overlap optimization

Recent advances in hydrogen internal combustion technologies highlight its potential for high efficiency and zero carbon emissions, offering a promising alternative to fossil fuels. This paper investigates the effects of valve timings and overlaps on engine performance, combustion characteristics, and emissions in a boosted direct-injection single-cylinder spark ignition engine using both gasoline and hydrogen. Optimized direct hydrogen injection effectively eliminates backfires and hydrogen slip during positive cam overlaps, significantly reducing the pumping mean effective pressure. The study’s primary finding demonstrates the potential of hydrogen to operate as a direct substitute for a gasoline engine without necessitating changes to the cam profiles at the high load operation. Furthermore, the study demonstrates that hydrogen leads to much higher thermal efficiencies across a wider range of engine loads when operated at a lean, air-to-fuel ratio of 2.75. The engine operating with such a lean-burn hydrogen mixture keeps the engine-out NOx emission at ultra-low levels. Compared to gasoline, hydrogen exhibits greater stability and a reduced reliance on camshaft timing during engine operation.

Theoretical thermal efficiencies of ideal, supercharged and gasoline engine cycles

This paper updated the perception of theoretical thermal efficiencies of reciprocating engine cycles by the analysis of six ideal cycles (Diesel, Joule-Brayton, Otto, Atkinson, Sabathe and Song). It was theoretically elucidated that more available energy remains in exhaust gas at higher load than at lower one, testifying that the exhaust waster energy recovery is more important at higher load than at lower one. A supercharged cycle was theoretically demonstrated to have lower thermal efficiency than its counterpart naturally-aspirated one, while supercharged engines had been always considered to have higher thermal efficiency. The thermal efficiencies of gasoline engines were first derived, testifying that a homogeneous spark-ignition gasoline engine at part-load has less thermal efficiency than its corresponding Otto cycle and can achieve a higher thermal efficiency by retarding (or advancing) inlet valve closing than by throttling intake flow.

Parameter optimization for two-stroke direct-injection spark-ignition aviation kerosene engine

The type of two-stroke spark-ignition(SI) engine is still the main power sources of small and medium unmanned aerial vehicles. A transition from gasoline to aviation kerosene or light diesel fuel and from carburetor or port-injection equipment to direct-injection(DI) equipment is prevailing. However, the performance of two-stroke DI-SI engine fueled with aviation kerosene is not very good under medium and high loads. Therefore, using the two-stroke DI-SI kerosene engine modified from port-injection SI gasoline engine as the research subject, the effects of different parameters on engine combustion and performance were studied and parameter optimization was also carried out at high loads. Based on the optimal fuel injection parameters, the influences of ignition time, compression ratio, scavenging/exhaust port area and scavenging/exhaust phase on the operating characteristics of two-stroke engine were analyzed. It was indicated that ignition timing, compression ratio and scavenging/exhaust phase have obvious impacts on engine performance, while the scavenging port area shows little impact on engine performance. An optimization calculation with genetic algorithm was made by determining the optimal values of six parameters such as compression ratio, ignition time, scavenging port area, exhaust port area, scavenging phase and exhaust phase. After optimization, the power(P) of the engine was increased by 7.6 % and the thermal efficiency(η) was enhanced by 3.2 % without knock. The results will lay a foundation for further design and research of two-stroke aviation RP-3 SI-DI engine.

Experimental Study of the Impact of Ethanol Content on Partially Premixed Combustion With Ethanol-Gasoline Blends

Abstract As ethanol production increases and the demand for gasoline in spark ignition engines decreases over the next few decades, the use of these fuels in compression ignition systems is expected to increase. This raises the question of how much ethanol-in-gasoline is the right blend for compression ignition. This work experimentally studied E10, E30, E50, E75, and E100 in a split injection partially premixed compression ignition strategy. It was found that, separately, the cool flame reactivity of E10 and the high cooling potential of E75 and E100 enable heat release rate control in partially premixed combustion. E30 and E50 did not show the same control authority. E30 performed the worst due to having a small amount of cool flame reactivity and a low cooling potential. It was found that NOx emissions were not significantly impacted by ethanol content, but the smoke emissions were. E100 produced near zero smoke, but all the ethanol-gasoline blends produced some smoke. When 20% of the fuel was injected during the mid-dle of the compression stroke, E10, E30, E50, and E75 all produced low, but nonzero smoke emissions. When the second injection was moved near top dead center, the smoke emissions of E75 stayed low but the smoke emissions of E10, E30, and E50 all rose to a filter smoke number greater than 0.3. These results indicate that low- and high-ethanol content gasolines are both viable paths forward for partially premixed combustion systems, but medium-ethanol content gasolines should be avoided.

Potential of Hydrogen Internal Combustion Engine for the Decarbonised Passenger Vehicle

CO2 regulations are becoming very stringent due to the goal of reducing greenhouse gases and achieving carbon neutrality. It has already become a common situation that electric vehicles are emerging as eco-friendly power systems rather than vehicles equipped with conventional internal combustion engines and their share in the market is increasing. However, even with an internal combustion engine, CO2 can be drastically reduced if a carbon-free fuel such as hydrogen is used. Raw nitrogen oxides (NOx) emissions can be overcome to a certain level through ultra-lean burn operation, but in order to balance the amount of hydrogen and air in the limited space of the combustion chamber, a drop in the engine’s maximum output should be accepted. Hyundai Motor Company (HMC) also previously developed an engine using hydrogen fuel (), but was unable to progress to mass production. Since then, hybrid technology has become popular, and with the development of hydrogen injection devices, an era has arrived where mass production becomes a possibility. For this reason, studies on internal combustion engines using hydrogen fuel based on existing spark ignition or compression ignition engines are rapidly increasing. In this study, a hydrogen fuel engine was designed and manufactured based on the mass produced gasoline spark ignition engine. CO2 level was confirmed from initial performance evaluation, and it was found that raw NOx levels and maximum power were in a trade-off relationship with each other under the same air-charging system application. In addition, the method to improve maximum engine torque was verified while maintaining the raw NOx level, and the maximum engine power improvement level was confirmed when raw NOx emissions were allowed to increase. Thereby the potential of the carbon-neutral internal combustion engine has been demonstrated.

Combustion and emission characteristics of a gasoline/ammonia fueled SI engine and chemical kinetic analysis of NOx emissions

Mitigating climate change involves the greater adoption of carbon–neutral and renewable energy sources within the transportation sector. Ammonia (NH3), as a carbon-free and sustainable fuel, has garnered growing interest in recent years. The present study aims to investigate the impact of NH3 blending on combustion and emission characteristics of a stoichiometric spark-ignition gasoline engine, with a particular emphasis on nitrogen-based emissions. The experimental investigation was complemented by chemical kinetic calculations. The results showed that NH3 blending could effectively suppress engine knock, optimize combustion phase and improve thermal efficiency. For pure gasoline, advancing the spark timing resulted in increased NOx emissions. However, when NH3 was blended, NOx emissions decreased with advancing spark timing, indicating a negative correlation with pressure. The NH3 emission was attributed to the ‘crevice mechanism’ as well as the absorption/desorption in the lubricant oil film on the cylinder wall. Chemical kinetic analysis revealed that the NOx emission from NH3 blended combustion is closely related to reactive radicals such as OH, H and O. The reduction in NOx emissions under high-pressure conditions was primarily attributed to the consumption of these reactive radicals via three-body reactions. Interestingly, NOx emissions initially increased with increasing NH3 blending ratio but eventually followed a decreasing trend. This can be attributed to the lower combustion temperature, lower concentration of reactive radicals, and enhanced de-NOx reactions.

Statistical analysis of flow field variations via independent component analysis

The link between in-cylinder flow and subsequent combustion in a single-cylinder gasoline spark-ignition engine is analyzed via independent component analysis (ICA). Experimentally, the two in-plane components of the velocity are measured in the central cylinder plane by high-speed particle image velocimetry (PIV) with the engine running slightly lean at 1500 rpm in skip-fired mode. In 213 cycles, measurements are made during the late compression stroke before ignition with approximately 1° crank-angle temporal resolution. ICA then decomposes the set of 213 flow fields at each time step, yielding a set of “source” flow patterns—the independent components (IC). The temporal coherence between the ICs is then examined in a persistence analysis, comparing each IC with the one from the previous time step starting at ignition timing and going backwards in time. The results show which ICs persist how long throughout the compression stroke. To investigate the link between the ICs and combustion, the crank angle at which 10% of the fuel are burned (CA10) in each cycle is correlated with the extent to which a given IC can be found in each flow field. The most persistent IC can be traced over more than half of the 70 degrees crank angle over which images were acquired. The IC that correlates best with CA10 visually more resembles some of the flow features found in conditional averaging of fast-burning versus slow-burning cycles.

Effect of gasoline-ethanol blends on the performance of a four stroke engine using Ricardo Wave software

Purpose The purpose of this study is to assess the performance of fuel blends containing ethanol and gasoline in spark ignition engines. The aim is to explore alternative fuels that can enhance performance while minimizing or eliminating adverse environmental impacts, particularly in the context of limited fossil fuel availability and the need for sustainable alternatives. Design/methodology/approach The authors used the Ricardo Wave software to evaluate the performance of fuel blends with varying ethanol content (represented as E0, E10, E25, E40, E55, E70, E85 and E100) in comparison to gasoline. The assessment involved different composition percentages and was conducted at various engine speeds (1,500, 3,000, 4,500 and 6,000 rpm). This methodology aims to provide a comprehensive understanding of how different ethanol-gasoline blends perform under different conditions. Findings The study found that, across all fuel blends, the highest brake power (BP) and the highest brake-specific fuel consumption (BSFC) were observed at 6,000 rpm. Additionally, it was noted that the presence of ethanol in gasoline fuel blends has the potential to increase both the BP and BSFC. These findings suggest that ethanol can positively impact the performance of spark-ignition engines, highlighting its potential as an alternative fuel. Originality/value This research contributes to the ongoing efforts in the automotive industry to find sustainable alternative fuels. The use of Ricardo Wave software for performance assessment and the comprehensive exploration of various ethanol-gasoline blends at different engine speeds add to the originality of the study. The emphasis on the potential of ethanol to enhance engine performance provides valuable insights for motor vehicle manufacturers and researchers working on alternative fuel solutions.

Efficient ELM Model With Parameter Optimization Using Pso Algorithms in the Prediction of Combustion Pressure Parameters of Dsi Engine Using Ethanol- Gasoline Blends

The present study focused mainly on developing PSO based ELM model to predict cylinder pressure associated parameters. Performance of PSO-ELM model then compared with ELM model to obtain its credential. For training and testing the models, data has been acquired through experiments on a Twin Spark Ignition (TSI) gasoline engine using EGB as fuel. The various operating variables are treated as input data whereas cylinder pressure associated parameters are treated as output data for the model. The result of the proposed modelling study indicated that PSO-ELM model has obtained the best performance with lowest value of MSE, MAPE (%) and hidden layer size as compared to ELM model. Hence PSO-ELM results in an efficient model structure with great generalization performance. Further, it is also observed that PSO-ELM takes more time as it calls for an iterative procedure for searching the optimal solution as compared to ELM, which takes only a single epoch.

Methanol (M85) Port Fuel-Injected Spark Ignition Motorcycle Engine Development—Part 1: Combustion Optimization for Efficiency Improvement and Emission Reduction

<div>Limited fossil fuel resources and carbonaceous greenhouse gas emissions are two major problems the world faces today. Alternative fuels can effectively power internal combustion engines to address these issues. Methanol can be an alternative to conventional fuels, particularly to displace gasoline in spark ignition engines. The physicochemical properties of methanol are significantly different than baseline gasoline and fuel mixture-aim lambda; hence methanol-fueled engines require modifications in the fuel injection parameters. This study optimized the fuel injection quantity, spark timing, and air–fuel ratio for M85 (85% v/v methanol + 15% v/v gasoline) fueling of a port fuel-injected single-cylinder 500 cc motorcycle test engine. Comparative engine performance, combustion, and emissions analyses were performed for M85 and baseline gasoline. M85-fueled engine exhibited improved combustion characteristics such as higher peak in-cylinder pressure, heat release rate, and cumulative heat release due to higher flame speed and the effect of fuel oxygen. The brake thermal efficiency increased by up to 23% at lower loads and 8% at higher loads for M85 fueling. Carbon monoxide was reduced by 11.4–94% and 46.1–94.4% for M85 w.r.t. baseline gasoline at 2500 and 3500 rpm, respectively, at varying engine loads. Hydrocarbon emissions showed mixed trends for M85 w.r.t. baseline gasoline. Nitric oxide emissions were 4–90.2% higher for M85 w.r.t. baseline gasoline at 2500 rpm, at varying engine loads; however, mixed trends were observed at 1500 and 3500 rpm. Carbon monoxide, hydrocarbons, and nitric oxide emissions were 4.6, 38.9, and 84.3% lower for M85 than baseline gasoline during idling. Overall the M85-fueled motorcycle engine emitted fewer harmful pollutants, indicating its superior environmental sustainability, except for slightly higher NO emission.</div>

Methanol as a fuel additive: effect on the performance and emissions of a gasoline engine

ABSTRACT The use of alternative fuels, such as alcohol-based fuels, has received a significant attention as a substitute for gasoline in spark-ignition engine. This study examines the influence of methanol-gasoline blends on both performance and emissions of a single-cylinder, spark-ignition engine. The engine is tested under full load conditions and at speeds range varying from 1000 to 3000 rpm. Four fuel blends labeled M0, M10, M20, and M40, were used, where the numbers represent the percentage by volume of methanol in the blend. It has been shown that the addition of methanol improves the power output and the torque of the engine. The highest improvement observed in engine power is 37% for M20 blend. Specific fuel consumption and thermal efficiency have also been improved with increasing methanol blending ratio. M40 showed a decrease in fuel consumption by 38% and an enhancement in thermal efficiency by 95%, at medium speed, compared to pure gasoline. Additionally, the results have shown significant reduction in CO and CO2 emissions, more particularly at low engine speeds (below 2000 rpm), where the addition of methanol (up to M40) has led to reducing CO emission with up to 70% compared to that of M0. However, NOx emissions increased with increasing methanol blending ratio. The highest increase in NOx levels was given by M40 by about 60% at low engine speed.

Extending ultra-lean burn performance of high compression ratio pre-chamber jet ignition engines based on injection strategy and optimized structure

The pre-chamber jet ignition technology significantly enhances the thermal efficiency and lean burn limit of the engine. In this study, a single-cylinder pre-chamber engine is subjected to a performance limit test. Through optimization of the pre-chamber fuel injection strategy, enhancement of the pre-chamber nozzle structure, and implementation of adiabatic piston technology, the gross indicated thermal efficiency of the spark ignition gasoline engine has successfully exceeded 51%, and the lean burn limit has been extended to lambda values greater than 3.1. For the selection of pre-chamber injection parameters, high injection pressure, minimal enrichment, and injection timing in the middle of the compression stroke are found to achieve both high fuel economy and lean burn performance. Moreover, the orientation of the pre-chamber nozzle has a significant impact on the lean burn performance of the engine, with the nozzle aiming at the top of the piston and avoiding pointing towards the cylinder wall. Under the conditions of high compression ratio and ultra-lean burn, the jet ignition followed by end-mixture gas auto-ignition results in a double-peak heat release process. Additionally, adiabatic piston technology shows potential in expanding the lean burn limit of engines while simultaneously mitigating HC emissions and engine heat transfer losses.

Effects of including a NOx storage component on a TWC when using a lean spark ignition gasoline engine combined with a passive SCR system✰

A three-way catalyst (TWC) and a TWC with a NOx storage component (NS-TWC) were evaluated on a lean spark ignition (SI) engine platform to reduce the fuel consumption and emissions of a passive selective catalytic reduction (pSCR) emission control system. The pSCR system is an approach for controlling NOx emissions from lean SI engines. It relies on onboard NH3 generation over a TWC during brief periods of fuel-rich operation. The NH3 is then stored on a downstream SCR catalyst and is available for NOx reduction during subsequent periods of lean engine operation. The NS-TWC addition enabled longer lean operation and more efficient NH3 use, which lowered fuel penalty of the pSCR system. Over a pseudo-transient drive cycle, the lean SI engine with pSCR that included NS-TWC demonstrated a 8.3% reduction in gasoline consumption over stoichiometric-only engine operation, and the NOx and non-CH4 organic gas emissions were consistent with Environmental Protection Agency (EPA) Tier 3 levels. The CO emissions, primarily from rich operation, exceeded the EPA Tier 3 levels. A cleanup catalyst (CUC) with high oxygen storage capacity was used to oxidize tailpipe CO during rich excursions by using the stored oxygen from the preceding lean operation. Although the CUC decreased CO emissions and reduced NH3 slip, some of the NH3 was converted back to NOx. Furthermore, rich CO control remains challenging. The results of this work demonstrate significant improvement in fuel consumption and emissions with a modified pSCR system architecture.

Numerical modeling of knocking combustion in spark ignition engines

At present, around 85% of the 1.1 billion passenger cars in the world are powered by gasoline spark ignition (SI) engines. Engine downsizing coupled with boosted operation and transition to sustainable fuels is considered an attractive strategy to enhance power density and reduce fuel consumption of SI engines. However, these operating conditions result in severe thermodynamic conditions, thereby promoting the likelihood of abnormal combustion phenomena such as knock. The severity of knock can vary significantly, and the efficiency of engines at high loads is limited in practice by heavy knocking phenomena. Since, a thorough analysis of such recurrent but non-cyclic phenomena via experiments alone becomes highly cumbersome, in the present work, a multi-cycle large-eddy simulation study was performed to quantitatively predict cyclic variability in the combustion process and cyclic knock intensity variability in a direct injection spark-ignition engine. For both the mild knock and heavy knock conditions, the numerical results were validated against experimental measurements. Based on the simulation results, a correlation analysis was performed considering combustion phasing, peak cylinder pressure and maximum amplitude of pressure oscillation. Furthermore, a detailed three-dimensional spatial analysis illustrated the evolution of auto-ignition kernel development and propagation of pressure waves during knocking combustion.

Reduction and thermodynamic treatment of NOx emissions in a spark ignition engine using isooctane and an oxygenated fuel (ethanol)

Abstract This research aims to study the effect of various blends of an alternative fuel environment (ethanol, isooctane) on the performance of a spark ignition gasoline engine. The blends were obtained from two additives: ethanol and isooctane. The tests were carried out on an engine test bench following DIN 70020. The results show that the petrol additives achieve excellent ecological results. On the other hand, the engine performance was slightly reduced compared with that obtained with pure fuel. We noted a variation in engine performance for the E10 (10% ethanol + 90% pure petrol) and I10 (10% isooctane + 90% pure petrol) blends, namely a reduction in nitrogen oxides (NOx) emissions of 7.5% for E10 and 5% for I10 compared with pure petrol. However, using E10 and I10 blends did not increase the specific fuel consumption. Thus, the increase in the octane rating resulted in a decrease in NOx emissions. The use of 96 octane fuels, which corresponds to I40 (40% isooctane + 60% petrol), is expected even though there is an 8% decrease in engine torque and a 5% decrease in power. We also noted that the blend (20% isooctane + 80% ethanol) led to a significant increase in NOx emissions, a significant increase in specific fuel consumption and a drop in performance (engine torque and power).

Response surface methodology application on lubricant oil degradation, performance, and emissions in SI engine: A novel optimization of alcoholic fuel blends.

For evaluating the significance of renewable alternative fuels for optimized engine performance and lower emissions, methanol has been extensively utilized as a blend with gasoline in spark-ignition engines. However, rare attempts have been rendered to examine the consequence of methanol-gasoline fuel blends (M6, M12, and M18) on lubricant oil operating for a longer period in engines. The highest and least decrease of 9.62% and 6.68% in kinematic viscosity (KV) was observed for M0 and M18, respectively. However, the flash point (FP) of degraded lubricant oil for M6, M12, and M18 was 3%, 5%, and 7% higher than that of M0, respectively. Total acid number (TAN) and ash content of degraded lubricant oil for M18 were the highest among M0, M6, and M12. An inclusive optimization of engine performance, emissions, and lubricant oil properties has been made for various methanol-gasoline fuel blends at distinct operating conditions by employing the response surface methodology (RSM) technique. RSM-based optimization portrayed the composite desirability value of 0.73 for 2137.13 watt brake power (BP), 6.08 N-m torque, 0.37 kg/kwh brake-specific fuel consumption, 22.10% brake thermal efficiency, 4.02% carbon monoxide emission, 7.15% carbon dioxide emission, 134.12 ppm hydrocarbon emission, 517.02 ppm nitrogen oxides emission, 12.44 cst KV, 203.77°C FP, 2.23 mg/g KOH TAN, and 2.65%wt ash content as responses for fuel blend M8 at 3400 rpm and higher loading condition. RSM predicted results demonstrated significant compliance with empirical findings, with absolute percentage error (APE) below 5% for each response. However, the highest APE of 4.68% was obtained for FP owing to inefficient desirability as a consequence of manual testing. The least APE of 1.57% was obtained for torque because of the highest desirability. Overall, the RSM predicted results of the designed models are effective and viable. RSM technique was found to be effective for the optimization of the broader engine characteristics spectrum.

Throttling Effect on the Performance and Emissions of a Multi-Cylinder Gasoline Fuelled Spark Ignition Engine

The throttle mechanism, a regulatory technique of engine output, is accompanied by a loss of some energy. The effect of intake air throttling on the performance and emissions of a multi-cylinder spark ignition gasoline engine was experimentally investigated. The engine was coupled to a hydraulic dynamometer equipped with a customized cooling system for both the engine and dynamometer. Experimental tests were performed for various engine speeds and air-fuel ratios at the WOT and POT conditions with optimized ignition timing. The acquired results recorded that a better engine operation could be achieved with WOT in terms of bmep, bsfc, ηb, CO, CO2 and UHC compared to POT. At the same time, the worst trend at WOT was noticed for the NOx concentration due to the higher conversion efficiency of fuel combustion. In terms of engine speed for both WOT and POT conditions, operating at 3000 rpm represents the minima of ϕ, bsfc, CO and UHC; and the maxima of ηb, CO2 and NOx with some fluctuation on both sides of this point. Maximum recorded values of ηb were about 30.55% and 28. 55%, while the minimum values of bsfc were about 274 and 293 g/kW.h for the WOT and POT conditions, respectively. The maximum bmep was obtained at 2500 rpm at WOT and POT conditions with values of about 940 kPa and 904 kPa, respectively. Maximum recorded values of NOx were about 1525 and 977 ppm for the WOT and POT conditions, respectively.

A numerical study on knock combustion suppression using targeted fuel injection in an SI engine

A novel concept to suppress knock combustion using the targeted fuel injection in a spark-ignition (SI) engine is proposed, which utilizes a customized injector to inject a small portion of the total fuel toward the end-gas region in the late compression stroke so that charge cooling effect by fuel vaporization is imposed on the local mixtures. CFD studies were carried out to evaluate the effects of various targeted fuel injection strategies on the processes of charge cooling, air-fuel mixing and combustion in a 1.2-L gasoline SI engine with a high compression ratio. A knock prediction model adopting a level set G-equation model coupled with a transported Livengood-Wu integral correlation was applied to predict the knock event by capturing the occurrence of end-gas auto-ignition. It was found that the local gas temperatures in the sprayed region decreased and knock combustion tendency was suppressed indeed, and the degree of the reduction in local gas temperature and knock tendency was affected by the selected targeted injection strategy. However, the results also indicated that excessive fuels injected could result in worsen air-fuel mixing that led to incomplete combustion. Hence, the injection strategy needs to be optimized by balancing the knock tendency and combustion efficiency. The study further shown that the spark timing could be advanced by 3.3° crank angle in a particular injection strategy case by comparing with the non-targeted-injection case, which demonstrated the effectiveness of the proposed concept.