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This study investigates the effect of hydrogen enrichment in a direct-injected methanol-fuelled SI engine, with combustion and emission performance analysed by varying the methanol injection timing from 150° to 60° CA bTDC. A three-dimensional computational fluid dynamic model of the hydrogen-enriched methanol engine was developed to predict the engine performance, in-cylinder, and emission characteristics. The numerical model was solved using three-dimensional Reynolds-Averaged Navier Stokes, the RNG k-epsilon model for turbulence, the O'Rourke and Amsden sub-model for heat transfer, the extended Zeldovich mechanism for nitric oxide emissions, and the Hiroyasu-NSC model for soot emissions. The results indicated that retarding the injection timing resulted in a decrease in the indicated specific CO and soot emissions along with a rise in the indicated specific NOx emissions. Furthermore, hydrogen enrichment with methanol enhanced the hydroxyl radical concentration, reduced the combustion duration, reduced also the indicated specific CO and soot emissions while increasing the indicated specific NOx emissions. The study indicates that hydrogen enrichment could extend the late injection timing limit of methanol by enhancing fuel-air mixing, which improves and controls the combustion process more effectively. • Hydrogen enrichment extended the late injection limit of methanol. • Injection timing improved fuel-air mixing and controlled combustion process. • Methanol performance was limited for high hydrogen additions. • Hydrogen addition to methanol enhanced mixing and combustion. [ABSTRACT FROM AUTHOR]

In the endeavor to accomplish a fully de-carbonized globe, sparkling interest is growing towards using natural gas (NG) having as vastly major component methane (CH4). This has the lowest carbon/hydrogen atom ratio compared to other conventional fossil fuels used in engines and power-plants hence mitigating carbon dioxide (CO2) emissions. Given that using neat hydrogen (H2) containing nil carbon still possesses several issues, blending CH4 with H2 constitutes a stepping-stone towards the ultimate goal of zero producing CO2. In this context, the current work investigates the exergy terms development in high-speed spark-ignition engine (SI) fueled with various hydrogen/methane blends from neat CH4 to 50% vol. fraction H2, at equivalence ratios (EQR) from stoichiometric into the lean region. Experimental data available for that engine were used for validation from the first-law (energy) perspective plus emissions and cycle-by-cycle variations (CCV), using in-house, comprehensive, two-zone (unburned and burned), quasi-dimensional turbulent combustion model tracking tightly the flame-front pathway, developed and reported recently by authors. The latter is expanded to comprise exergy terms accompanying the energy outcomes, affording extra valuable information on judicious energy usage. The development in each zone, over the engine cycle, of various exergy terms accounting too for the reactive and diffusion components making up the chemical exergy is calculated and assessed. The correct calculation of species and temperature histories inside the burned zone subsequent to entrainment of fresh mixture from the unburned zone contributes to more exact computation, especially considering the H2 percentage in the fuel blend modifying temperature-levels, which is key factor when the irreversibility is calculated from a balance comprising all rest exergy terms. Illustrative diagrams of the exergy terms in every zone and whole charge reveal the influence of H2 and EQR values on exergy terms, furnishing thorough information. Concerning the joint content of both zones normalized exergy values over the engine cycle, the heat loss transfer exergy curves acquire higher values the higher the H2 or EQR, the work transfer exergy curves acquire slightly higher values the higher the H2 and slightly higher values the lower the EQR, and the irreversibility curves acquire lower values the higher the H2 or EQR. This exergy approach can offer new reflection for the prospective research to advancing engines performance along judicious use of fully friendly ecological fuel as H2. This extended and in-depth exergy analysis on the use of hydrogen in engines has not appeared in the literature. It can lead to undertaking corrective actions for the irreversibility, exergy losses, and chemical exergy, eventually increasing the knowledge of the SI engines science and technology for building smarter control devices when fueling the IC engines with H2 fuel, which can prove to be game changer to attaining a clean energy environment transition. [ABSTRACT FROM AUTHOR]

This study investigated the performance, emission reactions, and combustion of liquefied petroleum gas (LPG) at various volumetric ratios with gasoline. The experiments were carried out on a single cylinder spark ignition (SI) engine at different engine loads (500 to 3000 W). In general, the use of LPG has a negative effect on performance and combustion, while making a positive contribution to emissions. The brake thermal efficiency (BTE) and brake specific fuel consumption (BSFC) values closest to 100% gasoline were obtained with 25% LPG and were lower by 0.36% and 4.55%, respectively. Conversely, using LPG resulted in lower emissions of carbon dioxide (CO2), hydrocarbons (HC), and carbon monoxide (CO). The lowest emissions were obtained with the use of 100% LPG as 0.5%, 65 ppm and 9.5%, respectively. Compared to 100% gasoline, 20.63%, 27.78% and 5.19% improvements were achieved. Finally, the cylinder gas pressure value was negatively affected using LPG. Compared to 100% gasoline, the gas pressure value obtained with 75% LPG content fuel was 7.81% lower. It has been concluded that LPG is an environmentally friendly alternative fuel in terms of emissions, and considering the decrease in performance values, 25% LPG can be used successfully in SI engines instead of 100% LPG. [ABSTRACT FROM AUTHOR]

An experimental investigation on the spatial distribution of knock events in a turbocharged spark-ignition engine for hybrid vehicle applications was conducted by using a multichannel fiber optic method. The knock positions were detected under different conditions to investigate the influence of crucial engine design and operating parameters on the knock characteristics including the spatial distribution in the combustion chamber and its relationship to knock intensity. The measured data reveal that the spatial distribution in the engine with a port fuel injection (PFI) system is mainly located on the exhaust side with insignificant influence of engine speed and load, which is attributed to the elevated thermal load around the exhaust valves. However, the knock events under gasoline direct-injection (DI) conditions were found to occur in more scattered locations with more occurring on the engine front-end and rear-end sides. These results indicate that the in-cylinder fuel-air mixing process may have a significant impact on the knock occurrence spots under DI conditions. The knock positions of the engine with different excessive air ratios, injection timings, and intake-valve timings were also detected, indicating that engine operating parameters have complex influences on the knock-region distribution in a DI engine. In addition, experiments were also carried out in two different cylinders to verify the cylinder-to-cylinder variations in knock regions which may be caused by the engine cooling design. Furthermore, no apparent correlations were observed between the knock position and the knock intensity by analysis of the experimental data. [ABSTRACT FROM AUTHOR]

In this study, the performance and exhaust emissions of a spark-ignition (SI) engine were simulated using AVL program, and the outcomes were compared with the results coming from experiments. The simulated engine was operated at a constant speed (1600 rpm) and various engine powers with gasoline (G100), and it blends with different higher-order alcohols such as 1-hexanol (HEX) and 1-heptanol (HP) as new fuel combinations. The proportions of tests fuel combinations were G100, G100 + HEX (5, 10, 15, and 20%) and G100 + HP (5, 10, 15, and 20%). The experimental study showed that the highest brake-specific fuel consumption was calculated to be 0.625 kg/kWh using HP20 fuel at 1 kW of engine power, while it was found to be 0.598 kg/kWh in the numerical study. The experimental research indicated that the lowest CO emission was emitted to be 0.28% in HEX20 fuel at 5 kW of engine power. Under the same condition, it was found 0.26% in the simulation study. The highest NOx emission was measured to be 1349.8 ppm in HEX20 fuel at 5 kW of the engine power. Meanwhile, 1318.3 ppm was found in the simulation. When the simulation outcomes were compared with the experimental study results, the simulation results were in valid. The difference in brake-specific fuel consumption results between experimental and numerical research ascended as the engine power jumped up. Furthermore, reductions were observed in the amount of difference in the results related to emissions between experimental and simulation studies at higher engine powers. [ABSTRACT FROM AUTHOR]

New generations of spark-ignition engines include exhaust gas recirculation (EGR) to improve the engine efficiency. Depending on the design of the EGR routing, some differences in the total amount of recirculated gases that reach each cylinder can be induced. This affects the air-to-fuel ratio on each cylinder due to the combination of the different temperature and composition of the gases at the intake valve closure. As a consequence, significant deviations in the combustion process and the subsequent composition upstream the three-way catalyst can be reached. This paper explores these effects on catalyst performance and tailpipe emissions, individualizing the behavior for each regulated species. The study was performed in a four-cylinder naturally aspirated engine with Atkinson cycle and a close-coupled three-way catalyst. The most significant deterioration in conversion efficiency appeared for the nitrogen oxides, directly linked to the EGR dispersion level. In the case of carbon monoxide (CO) emissions, no significant impact was observed except at high average EGR rates, where one or more of the cylinders exceeded the EGR tolerance for that speed and load. Based on these results, a strategy where the fuel injector command is adapted to correct the air-to-fuel ratio deviations induced by the EGR was developed and implemented. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

An optically accessible single-cylinder spark-ignition engine operated under homogeneous, part-load conditions is experimentally investigated using optical and spark diagnostics to evaluate the relationship between the spark, flow, and flame with increasing dilution using several levels of exhaust gas recirculation (EGR). Voltage and current measurements of the secondary spark circuit are compared with simultaneous high-speed spark plasma imaging, particle image velocimetry measurements of the flow field, and burned gas images. Specifically, characteristic restrike cycles and normal cycles are examined under the 0 % EGR and 12.9 % EGR conditions to reveal a relationship between the magnitude and direction of the velocity near the spark plug and the spark's behavior coupled with that of the subsequent flame propagation. Through the use of conditional statistics and correlation analysis of data sets of all non-restrike and all restrike cycles, the horizontal velocity across the spark gap was identified as a critical quantity in facilitating more stable and faster combustion under diluted mixture conditions. [ABSTRACT FROM AUTHOR]

In the endeavor to accomplish a fully de-carbonized globe, sparkling interest is growing towards using natural gas (NG) having as vastly major component methane (CH4). This has the lowest carbon/hydrogen atom ratio compared to other conventional fossil fuels used in engines and power-plants hence mitigating carbon dioxide (CO2) emissions. Given that using neat hydrogen (H2) containing nil carbon still possesses several issues, blending CH4 with H2 constitutes a stepping-stone towards the ultimate goal of zero producing CO2. In this context, the current work investigates the exergy terms development in high-speed spark-ignition engine (SI) fueled with various hydrogen/methane blends from neat CH4 to 50% vol. fraction H2, at equivalence ratios (EQR) from stoichiometric into the lean region. Experimental data available for that engine were used for validation from the first-law (energy) perspective plus emissions and cycle-by-cycle variations (CCV), using in-house, comprehensive, two-zone (unburned and burned), quasi-dimensional turbulent combustion model tracking tightly the flame-front pathway, developed and reported recently by authors. The latter is expanded to comprise exergy terms accompanying the energy outcomes, affording extra valuable information on judicious energy usage. The development in each zone, over the engine cycle, of various exergy terms accounting too for the reactive and diffusion components making up the chemical exergy is calculated and assessed. The correct calculation of species and temperature histories inside the burned zone subsequent to entrainment of fresh mixture from the unburned zone contributes to more exact computation, especially considering the H2 percentage in the fuel blend modifying temperature-levels, which is key factor when the irreversibility is calculated from a balance comprising all rest exergy terms. Illustrative diagrams of the exergy terms in every zone and whole charge reveal the influence of H2 and EQR values on exergy terms, furnishing thorough information. Concerning the joint content of both zones normalized exergy values over the engine cycle, the heat loss transfer exergy curves acquire higher values the higher the H2 or EQR, the work transfer exergy curves acquire slightly higher values the higher the H2 and slightly higher values the lower the EQR, and the irreversibility curves acquire lower values the higher the H2 or EQR. This exergy approach can offer new reflection for the prospective research to advancing engines performance along judicious use of fully friendly ecological fuel as H2. This extended and in-depth exergy analysis on the use of hydrogen in engines has not appeared in the literature. It can lead to undertaking corrective actions for the irreversibility, exergy losses, and chemical exergy, eventually increasing the knowledge of the SI engines science and technology for building smarter control devices when fueling the IC engines with H2 fuel, which can prove to be game changer to attaining a clean energy environment transition.

Notwithstanding the continuous technological development of spark-ignition engines, the physics of in-cylinder phenomena has not been explicitly clarified to date. Furthermore, the advent of diverse engine technologies and in-cylinder compositions has increased the difficulty of understanding these phenomena using existing analysis methods. Under those circumstances, the modeling based on the fundamental combustion behaviors is becoming critical for analyzing combustion. Built upon the zero-dimensional flame surface density model, therefore, the models proposed herein attempt to reproduce a vast majority of combustion behaviors revealed to date, such as differential diffusion, thermo-diffusive instability, cutoff scales, distributed reaction, and flame quenching. As a result, we successfully predicted the combustion of numerous operating points of four different SI engines, including the extremely lean operating points of gasoline/air mixture up to ϕ = 0. 53. Furthermore, the extensive thermodynamic ranges are explored for the validation of the models with the aid of continuously variable valve timing modules; the pressure and the calculated temperature of the unburned mixture at ignition timing are varied from 4.5 to 28.6 bar and 559–794 K, respectively. In this study, we suggest an expression for a fully-developed turbulent flame speed well-fitted with the explored ranges of chemical and thermodynamic states by inspecting the influencing factors for flame wrinkling. Additionally, we analyze combustion using the developed models and identify several distinctive features of both stoichiometric and lean-burn points. Lastly, this study reveals the importance of flame thickness (or inner cutoff), which has a comparable or more severe effect on early flame propagation compared to planar laminar flame speed. [ABSTRACT FROM AUTHOR]

This study developed a grid-connected biogas power generation system for a rural community using a 3-phase 2.2 kW squirrel-cage induction machine as the self-excited induction generator. The generator was driven by a 196 cc single-cylinder spark-ignition engine fueled by biogas. We developed a back-to-back converter that consists of a 3-phase PWM rectifier as the generator-side converter and a single-phase LCL-filtered grid-connected inverter. The generator-side converter transferred the active power to the grid-side converter and supplied the reactive power control back to the generator. The notch filter-based bus voltage control on the generator side mitigated the inter-harmonics in the generator current. The injected grid current complied with the IEEE 1547 standard because of the multi-frequency unbalanced synchronous reference frame control. The proposed system was validated with biogas produced from pig manure at a pig farm in central Thailand, which found a maximum output of 1.2 kW with a thermal system efficiency of 10.7%. The proposed system was scheduled to operate at 1.2 kW for 8 h per day with a levelized cost of 0.07 US$/kWh, 42% cheaper than the retail electricity price, and a payback period of 2.76 years. The proposed system is suitable for a farm with a minimum of 34 pigs. [ABSTRACT FROM AUTHOR]

Wiebe functions, analytical equations that estimate the fuel mass fraction burned (MFB) during combustion, have been effective at describing spark-ignition (SI) engine combustion using gasoline fuels. This study explores if the same methodology can be extended for SI combustion with syngas, a gaseous fuel mixture composed of H2, CO, and CO2, and anode-off gas; the latter is an exhaust gas mixture emitted from the anode of a Solid Oxide Fuel Cell, containing H2, CO, H2O, and CO2. For this study, anode off-gas is treated as a syngas fuel diluted with CO2 and vaporized water. Combustion experiments were run on a single-cylinder, research engine using syngas and anode-off gas as fuels. One single Wiebe function and three double Wiebe functions were fitted and compared with the MFB profile calculated from the experimental data. It was determined that the SI combustion process of both the syngas and the anode-off gas could be estimated using a governing Wiebe function. While the detailed double Wiebe function had the highest accuracy, a reduced double Wiebe function is capable of achieving comparable accuracy. On the other hand, a single Wiebe function is not able to fully capture the combustion process of a SI engine using syngas and anode off-gas. [ABSTRACT FROM AUTHOR]

In direct injection hydrogen engines, the Plume Ignition and Combustion Concept (PCC) developed by the authors has been applied to improve thermal efficiency and reduce NOx emissions under high-load operation. The PCC combustion method burns an optimized hydrogen jet plume that is ignited immediately upon completion of injection in the latter half of the compression stroke. In addition to optimizing the hydrogen jet configuration, this basic combustion concept was applied to burn a lean mixture and supercharging was used to recover the decline in power output due to combustion of a diluted mixture. As a result, a near-zero emission engine has been achieved that simultaneously provides high thermal efficiency, high power output and low NOx emissions at a single-digit ppm level. Various techniques have been applied to improve thermal efficiency further and achieve much lower NOx emissions close to a zero-emission target. These included the adoption of a re-entrant combustion chamber to reduce unburned hydrogen emissions, enhanced squish flow to promote better mixing of air and the hydrogen jet injected into the combustion chamber, and a narrower nozzle hole diameter to promote entrainment of air into the hydrogen jet. In this study, the effect of each of these measures was made clear experimentally and by analysis. This paper presents the results obtained. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental and a theoretical investigation made by simulations on a Renault HR09DET spark ignition engine, four-stroke, 3-cylinders, multipoint fuel injection fuelled successively by gasoline and compressed natural gas and hydrogen. The simulation model, developed with the AVL Boost program was calibrated using the experimental data obtained for a spark ignition engine fuelled with gasoline. The experimental data obtained on an engine test bench were compared with simulation results for gasoline and compressed natural gas fuelling. The simulation model allowed the addition of hydrogen in parallel with the fuelling by natural gas. The results highlight the advantages and disadvantages of operating a spark ignition engine with hydrogen enrichment of natural gas, in terms of regulated emissions as unburned hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxide emissions (NOx). As the amount of hydrogen in the mixture increases, up to 20%–30% volumetric fractions an extend in the combustion limits occurs associated to consistent reductions up to 65% for HC and 55% for CO. A slight decrease by an average of 15% occurs in NOx emissions for stoichiometric mixtures compared with gasoline. Considering the higher-octane number for Compressed Natural Gas (CNG) and hydrogen, the engine efficiency can be significantly improved by increasing the compression ratio up to the knock limit.

In this study, the response surface methodology was applied to verify the optimum compression ratio, methanol percentage, and engine load in order to obtain the best levels of engine response that will occur when using methanol (0, 10, and 20% by vol.) in a spark-ignition engine under different compression ratio (6.0:1, 8.0:1, and 10.0:1) and engine load (8, 10, and 12 kg) conditions. A response surface methodology aided by analysis of variance was created using the three-factor and three-level central composite full design with the results of the experiment. With the created model, optimum methanol percentage, compression ratio, and engine load levels corresponding to the finest brake thermal efficiency, brake-specific fuel consumption, carbon monoxide, carbon dioxide, hydrocarbon, and nitrogen oxide emission levels were determined. According to the optimization results, the optimum methanol percentage, compression ratio, and engine load were found to be 10.5%, 6.0:1, and 12 kg, respectively. Hydrocarbon, nitrogen oxide, carbon monoxide, carbon dioxide, brake thermal efficiency, and brake-specific fuel consumption corresponding to optimum operating conditions were determined as 63.568 ppm, 840.643 ppm, 0.365%, 14.059%, 28.199%, and 0.286 kg/kWh, respectively. To test the reliability of the response surface methodology results, experiments with optimal methanol, compression ratio, and engine load were carried out and compared with the response surface methodology findings. As a result, it can be said that the response surface methodology is a successful application for the optimization of a spark-ignition engine using methanol as an alternative fuel with different engine parameters. [ABSTRACT FROM AUTHOR]

Predicting turbulence in a zero-dimensional (0D) simulation is an undeniably challenging task due to the complexity of in-cylinder charge motion. In that respect, a physics-based understanding of in-cylinder flow phenomena is of vital importance for establishing high-fidelity 0D turbulence models under diverse engine conditions. The proposed 0D model is hence built upon the kinetic energy analyses of tumble, evidenced by three-dimensional computational fluid dynamics. Specifically, the overall 0D turbulence model consists of an intake model, a spinning up model, and a turbulence production model. The major difference between this model and the existing 0D turbulence models is that this model is grounded on a kinetic energy perspective of tumble, as opposed to an angular momentum perspective of tumble. That is, the behaviors of tumble, such as spinning up and vortex breakdown, are interpreted and modeled based on the changes in the kinetic energy of tumble. This enables the proposed model to secure wider applicability at various engine conditions, which were otherwise difficult to achieve. Therefore, the 0D simulation in this study was able to predict turbulent intensities at the conditions, differing in valve strategy, engine geometry, and engine operation, without changing any validation constants. Furthermore, along with the validation points used in this study, better predictions of turbulent intensity were achieved using the proposed model compared to the existing state-of-the-art model. [ABSTRACT FROM AUTHOR]

This work focuses on the numerical and experimental analysis of turbocharger selection and boost pressure effects on a CNG-fueled spark-ignition engine. Because of this, investigations are carried out on the influence of downsized compression ratio of 10.5:1 at different boost pressures and compared with a naturally aspirated compression ratio of 12.5:1. In order to perform the experimentation, a twin-cylinder, port fuel-injected, CNG engine with 15.5 kW at 3400 rpm is modified to utilize compressed bio-methane as fuel under 100% throttle condition. A simulation is performed to study the compressor impeller for T1 and T2 turbochargers using the ANSYS turbomachinery tool. Results indicate that the circumferential velocity of T1 is higher than of T2 at all boost pressures. Subsequently, experimentation is performed using T1 and T2 at three different boost pressure levels in a compression ratio of 10.5:1 at 1.1, 1.3, and 1.5 bar. T2 developed a maximum boost pressure of 1.1 bar compared to T1. T1 is chosen for further experimentations. At 1.3 bar of boost pressure, a rise in brake power was recorded by 19.3% compared to 12.5:1 under the naturally aspirated mode. Consequently, there is a reduction in fuel consumption by 10.1%, and hydrocarbon, carbon monoxide, and carbon dioxide emission levels reduce by 25%, 8.2%, and 4.9%, respectively. Therefore, turbocharging at a lower compression ratio exhibits better performance and reduces emissions compared to a higher compression ratio under naturally aspirated mode. [ABSTRACT FROM AUTHOR]

Biogas is a renewable gaseous fuel and has the potential to replace fossil fuels for spark-ignition engines; however, a higher volumetric proportion of CO2 in biogas degrades the engine characteristics significantly. Biogas upgradation techniques are limited by higher fuel costs, and strenuous modifications would be required for improving engine physical parameters. In this study, experimental investigations were performed with hydrogen-enriched biogas to enhance low operating load limit and engine characteristics, and to the best of authors' knowledge, studies related to operating range and low load enhancement by hydrogen addition in biogas fueled engines are not reported in literature. Gaseous-fuels blending setup was developed to fabricate the gaseous fuel mixtures in desired proportions and moderate amounts of hydrogen (5, 10, 20, and 30% by vol.) were blended with biogas. The experiments were conducted on a single-cylinder SI engine operated at the compression ratio of 10:1 and 1500 rpm for stationary applications. It was found that the coefficient of variation (COV) of indicated mean effective pressure decreased from 10% in case of biogas to 8.69, 6, 3.05, and 1.66%, respectively, for 5, 10, 20, and 30% hydrogen cases at 6 N·m loading condition. Low operating load limit enhanced from 6 N·m in case of biogas to 5.3, 2.2, 1.5, and 0.8 N·m, respectively, for 5, 10, 20, and 30% of hydrogen share in the fuel mixture and brake thermal efficiency also improved with hydrogen enrichment. Carbon-based emissions decreased with hydrogen addition, whereas oxides of nitrogen increased but it was well below the baseline case with pure methane. Overall results indicated that hydrogen enrichment enhances the low load limit and engine characteristics of biogas-fueled SI engines for stationary power generation applications in rural areas. [ABSTRACT FROM AUTHOR]

Both the shift from fossil to alternative fuels and the implementation of a pre-chamber combustion system allow for an increase in the efficiency of an internal combustion engine through optimizing its combustion process, while simultaneously reducing the engine-out emissions. The combination of alcohol-based fuels and pre-chamber combustion concepts has not been investigated on spark-ignition engines with high compression ratios in a passenger car size. This study presents investigations to show the potential in maximum achievable lean limit and net indicated efficiency. In particular, we present investigations of two alternative alcohol fuels on a direct-injection spark-ignition single-cylinder research engine for passenger car applications with a compression ratio of 16.4. The engine was operated with both an active and a passive pre-chamber, and the experimental results were compared to those of conventional spark-ignition operation. Direct injection was used for both the main combustion chamber and the pre-chamber. Methanol and ethanol were used as fuels for the main combustion chamber, whereas exclusively ethanol was used for the pre-chamber fueling. The performance of the alcohol fuels in all combustion configurations was evaluated in both part-load and high-load conditions. In particular, investigations of the combustion behavior over a variation of the excess air ratio at indicated mean effective pressures of 6 and 15 bar were performed. It can be concluded that with the use of methanol as fuel for the main combustion chamber, both higher excess air ratios and higher indicated efficiencies were achieved compared to the use of ethanol as the main combustion chamber fuel. In particular, a maximum net indicated efficiency of 48% at an excess air ratio of 2.0 was achieved with methanol. Moreover, active pre-chamber operation extended the lean limit to an excess air ratio of 2.3 compared to the maximum lean limit of 1.7 in passive pre-chamber operation. [ABSTRACT FROM AUTHOR]

With its unique qualities, such as infinite supply, high octane number, and capacity to cut greenhouse gas emissions, alcohol is a viable alternative fuel for SI engines. This review article aims to reveal to readers the effects of alcohol on the performance, combustion behavior, and emission characteristics of SI engines by collecting the outcomes from previous research. This article looks at methanol, ethanol, and butanol fuel qualities. The performance of SI engines with butanol, ethanol, and methanol combined with gasoline is investigated in terms of brake torque, brake power, fuel consumption, thermal efficiency, volumetric efficiency, mean effective pressure, and coefficient of variation under various conditions. Second, in-cylinder pressure, mass fraction burnt, ignition delay, pressure increases, and heat release rates are also used to evaluate the combustion characteristic. Finally, the article discusses pollutant emissions such as CO, CO2, NOx, UHC, and exhaust gas temperature. Methanol, ethanol, and butanol mixed with gasoline increased fuel consumption and lowered spark-ignition engines' thermal efficiency. When alcohol was combined with gasoline, most research found that CO, NOx, and UHC emissions were reduced due to improved combustion. [ABSTRACT FROM AUTHOR]

Non-carbon nature and higher hydrogen energy density of ammonia have gained a lot of interest as an energy asset and green fuel. In this work, the effects of ammonia fuel share and engine operating load on the combustion stability and engine characteristics (combustion and performance) of gaseous (NH 3 /CH 4) fuelled SI engine have been reported. The lower heating value and flame propagation speed of fuel mixture reduce with the increase in ammonia share (0–60% at 8 Nm engine load) and thus results in detrimental engine performance and higher cycle-to-cycle combustion variations (1.36%–14.9% COV of IMEP). A rise in operating load from 8 Nm to 16 Nm increases the flame propagation speed of the fuel mixture (60% ammonia share) and improves engine performance and combustion stability (14.9%–4.3% COV of IMEP). The results of this study indicate that the substitution of methane with ammonia could be maximized at higher engine operating loads to get the benefit of clean fuel utilization. [Display omitted] • Green ammonia as a hydrogen energy carrier and potential fuel for IC engines. • Study on the effect of ammonia addition in methane fuelled Spark Ignition engine. • Increasing share of NH 3 in fuel mixture at lower loads reduced combustion stability. • Enhancement of operating limits at higher engine loads in methane fuelled engines by NH 3 addition. [ABSTRACT FROM AUTHOR]

Hydrogen combustion engines are considered one of the leading solutions for decarbonizing road transport, mainly due to the possibility of adapting current engines for hydrogen operation with minor changes. This research extensively analyzes the effect of combined EGR (exhaust gas recirculation) and VVT (variable valve timing) strategies on the performance and emissions of a commercial turbocharged SI engine fueled with hydrogen. To this end, a 1D model of the said engine, widely validated for gasoline operation, was adapted to simulate the engine's behavior with hydrogen. This adaptation involved hardware changes and the implementation of a predictive hydrogen combustion submodel, previously calibrated using experimental data from a single-cylinder engine of similar geometry. Firstly, 400 hydrogen engine simulations without EGR were conducted to optimize the VVT system for fuel efficiency over a wide operating range. A detailed explanation of the causality of varying valve overlap on pumping losses, in-cylinder gas composition, and combustion is provided from these simulations. Then, a series of EGR sweeps were simulated to study its impact on performance and NOx at various degrees of load; concluding that diluting with EGR, rather than air, leads to reduced NOx emissions in exchange for slightly increased fuel consumption. • Adaptation of a Euro 6 turbocharged DI SI engine for hydrogen operation • Deep analysis of the VVT and EGR impact on thermal efficiency and emissions • EGR dilution is more effective in reducing NO X but penalizes fuel consumption • EGR leads to a low-end torque increase of 5–16% at iso-NO X conditions [ABSTRACT FROM AUTHOR]

Reynolds-Averaged Navier–Stokes (RANS) simulations of a spark-ignition engine are performed to examine different modes of hydrogen combustion under a large range of conditions. Twelve cases featuring different spark timings, equivalence ratios, and compression ratios are simulated. A consistent methodology is used across all cases without any adjustment to the turbulent flame speed model constant. A rigorous validation against the experimental data is also undertaken. The simulations capture four distinct combustion modes: normal, knocking, superknock or detonation and fast flame propagation. Specifically, for the fast flame propagation mode, a relatively fast spark-ignited flame is observed at lower compression ratios under stoichiometric conditions, resulting in large pressure fluctuations within the engine. It is also shown that the competition between flame timescale and ignition delay plays a crucial role in characterising the combustion mode under various conditions. • Hydrogen combustion in a CFR engine is simulated using RANS under a large range of operating conditions. • The simulation results are validated using the in-cylinder experimental pressure trace for all cases with consistent numerical settings. • Normal and knocking combustion, fast flame propagation, and detonation are all well captured in the simulations. • Fast propagation of hydrogen flame can cause large pressure oscillations without featuring end-gas auto-ignition. • Different combustion modes can be effectively characterised using both the premixed flame timescale and the ignition delay time of the end-gas. [ABSTRACT FROM AUTHOR]

This present study showed a comprehensive analysis of energy, exergy, performance, and emission characteristics of a spark-ignition engine powered by blends of gasoline-isoamyl alcohol-ethanol at volume proportions (100_0_0)% (P0E0), (90_5_5)% (P5E5), (80_5_15)% (P5E15), and (70_5_25)% (P5E25) at various engine speeds and compression ratios (CR). The outcomes of thermodynamic analyses revealed that the highest exergy and energy efficiency were 28.92 % (P0E0, 2600 rpm, CR of 9:1) and 31.01 % (P0E0, 2600 rpm, CR of 9:1), respectively. In addition, the average brake power and brake thermal efficiency for P0E0, P5E5, P5E15, and P5E25 increased by (30.36 %, 27 %, 26.74 %, 27.84 %) and (0.34 %, 0.07 %, 0.35 %, 0.33 %) respectively, while brake specific fuel consumption decreased by (2.5 %, 0.64 %, 3.62 %, 6.33 %) in the engine speed range of 2600–3200 rpm. Compared to gasoline, the maximum reduction of carbon monoxide emissions was 6.13 %, 8.81 %, and 9.96 %, while unburnt hydrocarbon emissions exhibited the maximum decrement by 5.8 %, 10.75 %, 12.58 % for P5E5, P5E15, and P5E25, respectively. However, nitrogen oxide (NOx) emissions for P5E25 tended to increase significantly compared to P0E0, while the difference in NOx emissions for P5E15 and P0E0 was marginal. Overall, P5E15 could be considered as the potential alternative fuel for spark-ignition engines towards the goal of sustainable energy conversion. [Display omitted] • Gasoline and ethanol blends with 5 % of isoamyl alcohol were used for all tests. • Energy, exergy, performance, and emission analysis were conducted in an SI engine. • The highest exergy and energy efficiency for blends exhibited at 3000 rpm. • Addition of ethanol and isoamyl alcohol to gasoline lowered pollutant emissions. [ABSTRACT FROM AUTHOR]

The Plume Ignition and Combustion Concept (PCC) developed by the authors significantly reduced nitrogen oxide (NOx) emissions in a direct-injection hydrogen engine under high-load operation. With PCC, a rich fuel plume is ignited immediately after completion of injection in the latter half of the compression stroke to reduce NOx formation. Simultaneously, high thermal efficiency was also achieved by mitigating cooling losses through optimization of the jet configuration in the combustion chamber. This basic combustion concept was applied to burn lean mixture in combination with the optimized hydrogen jet configuration and the application of supercharging to recover the power output decline due to the use of a diluted mixture. As a result, a near-zero-emission-level engine has been achieved that simultaneously provides high thermal efficiency, high power output and low NOx emissions at a single-digit ppm level [1]. In this study, a high compression ratio was applied to improve thermal efficiency further by taking advantage of the characteristics of hydrogen fuel, especially its diluted mixture with a high anti-knock property. As a result, NOx emissions at a single-digit ppm level and gross indicated thermal efficiency of 52.5% were achieved while suppressing knocking at a compression ratio of 20:1 by optimizing the excess air ratio and injection timing, and increasing power output by supercharging. Fig. 11 Relationships between η i and NOx Emissions, p i, and CPO Intensity for Higher Compression Ratios and the Same Relationships to Show the Effect of Supercharging (p i + and η i + are used for SC, p i and η i for NA, respectively). [Display omitted] • Maximum ITE of 53% was obtained by raising the CR to 20:1 in a jet-plume-controlled DI lean burn hydrogen engine. • Supercharging achieved gross ITE of 52.5% while keeping NOx emissions to a single-digit-ppm level. • Knocking noise and damages on surrounding component were not observed in the output range evaluated in this research. [ABSTRACT FROM AUTHOR]

Limitations on the upgradation of biogas to biomethane in terms of cost effectiveness and technology maturity levels for stationary power generation purpose in rural applications have redirected the research focus towards possibilities for enhancement of biogas fuel quality by blending with superior quality fuels. In this work, the effect of hydrogen enrichment on performance, combustion and emission characteristics of a single-cylinder, four-stroke, water-cooled, biogas fuelled spark-ignition engine operated at the compression ratio of 10:1 and 1500 rpm has been evaluated using experimental and computational (CFD) studies. The percentage share of hydrogen in the inducted biogas fuel mixture was increased from 0 to 30%, and engine characteristics with pure methane fuel was considered as a baseline for comparative analysis. The CFD model is developed in Converge CFD software for a better understanding on combustion phenomenon and is validated with experimental data. In addition, the percentage share of hydrogen enrichment which would serve as a compromise between biogas upgradation cost and engine characteristics is also identified. The results of study indicated an enhancement in combustion characteristics (peak in-cylinder pressure increased; COV IMEP reduced from 9.87% to 1.66%; flame initiation and combustion durations reduced) and emission characteristics (hydrocarbon emissions reduced, and NOx emissions increased but still lower than pure methane) with increase in hydrogen share from 0 to 30% in biogas fuelled SI engine. Flame propagation speed increased and combustion duration reduced with hydrogen supplementation and the same was evident from the results of the CFD model. Performance of the engine increased with increase in hydrogen share up to 20% and further increment in hydrogen share degraded the performance, owing to heat losses and the enhancement in combustion characteristics were relatively small. Overall, it was found that 20% blending of hydrogen in the inducted biogas fuel mixture will be effective in enhancing the engine characteristics of biogas fuelled engines for stationary power generation applications and it holds a good compromise between biogas upgradation cost and engine performance. • Comparative study on characteristics of SI engine fuelled with methane, biogas and hydrogen enriched biogas. • Effect of hydrogen enrichment on characteristics of biogas fuelled engine. • Detailed analysis of in-cylinder combustion by computational approach (CONVERGE CFD). • 20% blending of hydrogen in biogas was observed to be effective. [ABSTRACT FROM AUTHOR]

This study developed a grid-connected biogas power generation system for a rural community using a 3-phase 2.2 kW squirrel-cage induction machine as the self-excited induction generator. The generator was driven by a 196 cc single-cylinder spark-ignition engine fueled by biogas. We developed a back-to-back converter that consists of a 3-phase PWM rectifier as the generator-side converter and a single-phase LCL-filtered grid-connected inverter. The generator-side converter transferred the active power to the grid-side converter and supplied the reactive power control back to the generator. The notch filter-based bus voltage control on the generator side mitigated the inter-harmonics in the generator current. The injected grid current complied with the IEEE 1547 standard because of the multi-frequency unbalanced synchronous reference frame control. The proposed system was validated with biogas produced from pig manure at a pig farm in central Thailand, which found a maximum output of 1.2 kW with a thermal system efficiency of 10.7%. The proposed system was scheduled to operate at 1.2 kW for 8 h per day with a levelized cost of 0.07 US$/kWh, 42% cheaper than the retail electricity price, and a payback period of 2.76 years. The proposed system is suitable for a farm with a minimum of 34 pigs.

Hydrogen and ammonia are primary carbon-free fuels that have massive production potential. In regard to their flame properties, these two fuels largely represent the two extremes among all fuels. The extremely fast flame speed of hydrogen can lead to an easy deflagration-to-detonation transition and cause detonation-type engine knock that limits the global equivalence ratio, and consequently the engine power. The very low flame speed and reactivity of ammonia can lead to a low heat release rate and cause difficulty in ignition and ammonia slip. Adding ammonia into hydrogen can effectively modulate flame speed and hence the heat release rate, which in turn mitigates engine knock and retains the zero-carbon nature of the system. However, a key issue that remains unclear is the blending ratio of NH3 that provides the desired heat release rate, emission level, and engine power. In the present work, a 3D computational combustion study is conducted to search for the optimal hydrogen/ammonia mixture that is knock-free and meanwhile allows sufficient power in a typical spark-ignition engine configuration. Parametric studies with varying global equivalence ratios and hydrogen/ammonia blends are conducted. The results show that with added ammonia, engine knock can be avoided, even under stoichiometric operating conditions. Due to the increased global equivalence ratio and added ammonia, the energy content of trapped charge as well as work output per cycle is increased. About 90% of the work output of a pure gasoline engine under the same conditions can be reached by hydrogen/ammonia blends. The work shows great potential of blended fuel or hydrogen/ammonia dual fuel in high-speed SI engines.

The indicated mean effective pressure (IMEP) is a key parameter for measuring the power output of an internal combustion engine (ICE). This indicator can be used to locate the high efficiency regions of engines. Therefore, it makes sense to predict the IMEP based on the machine learning (ML) approaches. However, different ML models are applicable to different scenarios, so it is important to choose the right model for prediction. The objective of this paper was to compare three ML models' (ANN, SVR, RF) predictive performance in forecasting IMEP indicator with the input parameters spark timing (ST), speed and load. A validated one-dimensional (1D) computational fluid dynamics (CFD) model was employed to provide 756 sets of data for the training, validation, and testing of the model. The results indicated that the random forest (RF) model had the worst prediction performance, and support vector regression (SVR) had a slightly better prediction performance than the artificial neural network (ANN), at least for the investigations in this study. Overall, the ANN and SVR models showed good predictive performance for IMEP, as the coefficient of determination (R2) was close to unity, and the root mean squared error (RMSE) was close to zero. Whereas the overall prediction results of the RF model are acceptable, the RF model does not learn well for some internal engine laws. [ABSTRACT FROM AUTHOR]

The contribution of this article is to propose a knock controller based on the estimation of the distribution quantile of the knock intensity measurements. Despite the quantile estimation randomness, the corrections undertaken by the controller are moderated by the level of confidence in the quantile estimation. This strategy offers a fast control ensuring a better compromise between the engine efficiency and the prevention of knock phenomenon. The design of the controller reduces the engine torque fluctuations and is suited for engine transient operations. [ABSTRACT FROM AUTHOR]

A shift toward a circular and C O 2 -neutral world is required, in which rapid defossilization and lower emissions are realized. A promising alternative fuel that has gained traction is methanol, thanks to its favorable and clean-burning fuel properties as well as its ability to be produced in a carbon-neutral process. Especially methanol's high knock resistance and its combustion stability offer the opportunity to operate an engine at both a high compression ratio and a high excess air dilution. Although methanol has been investigated in series-production engines for passenger car applications, there is a lack of investigations on a dedicated engine that can operate at methanol's knock limit. In this paper, methanol's knock limitation is experimentally assessed by applying high compression ratios to a direct injection spark-ignition single-cylinder research engine. To that end, four compression ratios were investigated: 10.8, 15.0, 17.7, and 20.6. With compression ratios of 15.0 and 17.7, the lean-limit was increased to excess air ratios of 2.0 and 2.1, respectively, compared to 1.7 at a compression ratio of 10.8. For the highest compression ratio of 20.6, the maximum lean burn limit was increased to an excess air ratio of 1.9 due to achieving the maximum cylinder pressure limit. Despite the minor increase in lean-limit, a maximum indicated efficiency of 48.7% was achieved with the highest compression ratio of 20.6. However, even at this high compression ratio, methanol did not show a knock limitation. The investigations in this work provide profound knowledge for future engine investigations with methanol. [ABSTRACT FROM AUTHOR]

Besides electrification of the powertrain, new synthetic alternative fuels with the potential to be produced from renewable sources come into focus. Methanol is the most elementary liquid synthetic fuel and no novelty for use in internal combustion engines. This article presents pathways to achieve high efficiency spark-ignition methanol combustion on a direct injection spark-ignition single-cylinder research engine with two different stroke-to-bore ratios (1.2 and 1.5) and a constant bore. In addition, two compression ratios (CRs) were investigated on each setup: CR = 10.8 using RON95 E10 gasoline fuel and a higher CR = 15 using neat methanol. In contrast to previous studies of stroke-to-bore ratio influences on SI combustion, this article aims at demonstrating how the advantages of a high stroke-to-bore ratio can be exploited by combining a long-stroke engine with increased compression ratios and methanol. The increased stroke enhances the tumble motion due to a higher piston speed and a larger compression volume which improves the mixture homogenization and combustion velocity. Moreover, the lower surface/volume ratio results in a reduced heat transfer. When using RON95E10 gasoline fuel and CR = 10.8, an efficiency gain of up to 1.6% could be achieved with the long-stroke compared to the short-stroke especially at lower engine loads. With methanol and CR = 15, an efficiency gain of up to 1.6% could be achieved with the long-stroke setup compared to the short-stroke engine. Subsequently, lean burn conditions were experimentally investigated with methanol and CR = 15. The longer stroke allowed the lean burn limit to be extended from λ = 1.9 to λ = 2.0 with an efficiency gain of up to 2.2%. A maximum indicated efficiency of 47.4% could be achieved at λ = 1.9 with methanol on the long-stroke engine with CR = 15. [ABSTRACT FROM AUTHOR]

In-cylinder expansion of internal combustion engines based on Diesel or Otto cycles cannot be completely brought down to ambient pressure, causing a 20% theoretical energy loss. Several systems have been implemented to recover and use this energy such as turbocharging, turbomechanical and turbo-electrical compounding, or the implementation of Miller cycles. In all these cases however, the amount of energy recovered is limited allowing the engine to reach an overall efficiency incremental improvement between 4% and 9%. Implementing an adequately designed expander-generator unit could efficiently recover the unexpanded exhaust gas energy and improve efficiency. In this work, the application of the expander-generator unit to a hybrid propulsion vehicle is considered, where the onboard energy storage receives power produced by an expander-generator, which could hence be employed for vehicle propulsion through an electric drivetrain. Starting from these considerations, a simple but effective modeling approach is used to evaluate the energetic potential of a spark-ignition (SI) engine electrically supercharged and equipped with an exhaust gas expander connected to an electric generator. The overall efficiency was compared to a reference turbocharged engine within a hybrid vehicle architecture. It was found that, if adequately recovered, the unexpanded gas energy could reduce engine fuel consumption and related pollutant emissions by 4-12%, depending on overall power output. [ABSTRACT FROM AUTHOR]

Increasing the compression ratio is one of the methods to increase the thermal efficiency of a gasoline spark-ignition (SI) engine. However, this exposes the end-gas to thermodynamic conditions that are prone to cause spontaneous ignition. The resulting knock acts as a barrier to the thermal efficiency improvement, and thus, may offset the thermal efficiency benefit of the high compression ratio. In this study, performance and knock characteristics with different coolant flow directions and coolant temperatures were evaluated in a port fuel injection SI gasoline engine with a compression ratio of 14. The coolant temperature was reduced to suppress the knock. Although the knock was accordingly suppressed, the fuel consumption increased because of the increase in the heat loss. From a knock sensor analysis, the knock was mainly found in the exhaust side. Therefore, the coolant flow direction from the intake to the exhaust in the baseline engine head was changed to the opposite direction in a modified engine head for suppressing the knock in the exhaust side. The change in the coolant flow direction resulted in knock suppression as well as fuel consumption reduction. [ABSTRACT FROM AUTHOR]

Ethanol, produced from biomass, is a renewable fuel that can be an attractive alternative fuel to gasoline for the increasing concerns of energy security and the environment. In the present work, combustion characteristic of ethanol (E100) fueled spark-ignition engine is compared with base gasoline fuel, and consecutively evaluated the cycle-to-cycle variations (CCV) of the engine parameters. These investigations were performed on a 250cc air-cooled four-stroke single-cylinder port-fuel injection spark-ignition engine. The engine was operated at 3500 rpm and 4000 rpm of engine speed while maintaining the same loads for ethanol and gasoline. It was found from the results that the peak in-cylinder pressure (Ppeak) is lower with ethanol than gasoline at a given load. The Ppeak decreased from 27.5 to 25.5 bar when ethanol was used in the engine at 3500 rpm and 5 Nm load instead of gasoline. Moreover, the mass fraction burned of the air-fuel mixture was faster for ethanol as compared to gasoline. The CCV analysis showed that CCV of Ppeak and location of Ppeak (IMEP) were lowered for ethanol compared to gasoline. A decrement in the coefficient of variation (COV) of Ppeak and IMEP from 11.6% to 8.3% and 12.6% to 11.7%, respectively, were observed when ethanol was utilized in the engine instead of gasoline at 3500 rpm and 5 Nm load. This resulted in a decrease in the COV of IMEP and engine speed by 2.8% and 0.25%, respectively, for ethanol as compared to gasoline. This study indicates that the combustion stability is better for ethanol-fueled spark ignition engine as compared with gasoline fuel. [ABSTRACT FROM AUTHOR]

In this study, the response surface methodology (RSM) was used to optimize the addition of different amounts of manganese to a spark-ignition (SI) engine operating with alcohol–gasoline fuel blend. The content of the fuel blend used was set to 7.5% fusel oil, 7.5% ethanol and 85% gasoline. By adding 4, 8, 12 and 16 ppm manganese to this fuel mixture, tests were carried out at different engine speeds (2500, 2750, 3000 and 3250 rpm). An analysis of variance (ANOVA)-supported RSM model was created to determine the optimum engine speed/manganese amount and responses according to optimum engine conditions. According to the optimization results obtained from RSM, the optimum manganese amount and engine speed were found as 3 ppm and 2650 rpm, respectively. In addition, the responses according to optimum engine conditions are 26.237 Nm, 8.262 kW, 385.749 g/kWh, 666.924 °C, 7.079%, 34.3115 ppm, 7.921% and 140.428 ppm for torque, power, brake specific fuel consumption (BSFC), exhaust gas temperature (EGT), carbon monoxide (CO), hydrocarbon (HC), carbon dioxide (CO2) and nitrogen oxide(NOx), respectively. Moreover, according to the validation tests for the reliability of the optimization results, the error rates were below 10%. Based on these results, it can be said that RSM can successfully determine the amount of manganese to be added to the SI engine operating with dual alcohol/gasoline blends. [ABSTRACT FROM AUTHOR]

The authors have proposed a new combustion process called the Plume Ignition Combustion Concept (PCC), in which with an optimal combination of hydrogen injection timing and controlled jet geometry, the plume of the hydrogen jet is spark-ignited to accomplish combustion of a rich mixture. This combustion process markedly improves thermal efficiency by reducing cooling loss, which is essential for increasing thermal efficiency in a hydrogen engine while maintaining high power. In order to improve thermal efficiency and reduce NOx formation further, PCC was applied to a lean-burn regime to burn a leaner mixture globally. In this study, the effect of supercharging which was applied to recover the reduced output power due to the leaner mixture on improving thermal efficiency was confirmed along with clarifying the cause. [Display omitted] • Supercharging improves the thermal efficiency, high output, and NOx emissions of a direct-injection hydrogen engine. • Major factors that improve thermal efficiency by supercharge are reduction of cooling loss and unburned hydrogen. • Optimization of SOI timing and λ is important for achieving high efficiency and near-zero NOx emissions. [ABSTRACT FROM AUTHOR]

The work is devoted to an experimental and design-theoretical analysis of combustion regimes of depleted compositions of gas mixtures based on hydrogen and syngas in the combustion chamber of a spark-ignition internal combustion engine. The analysis made points to the energy advantages of use of syngas compared to hydrogen. Here, on the one hand, it has been shown that the indicated efficiency is weakly dependent on the excess-hydrogen coefficient, which allows the conclusion on the expediency of utilization of depleted compositions as more environmentally safe ones. On the other, the existence of a certain concentration limit has been demonstrated below which a significant underburning of a fuel–air mixture, including that determined by the dynamics of the combustion front in the combustion chamber of the internal combustion engine, is observed. [ABSTRACT FROM AUTHOR]

With its unique qualities, such as infinite supply, high octane number, and capacity to cut greenhouse gas emissions, alcohol is a viable alternative fuel for SI engines. This review article aims to reveal to readers the effects of alcohol on the performance, combustion behavior, and emission characteristics of SI engines by collecting the outcomes from previous research. This article looks at methanol, ethanol, and butanol fuel qualities. The performance of SI engines with butanol, ethanol, and methanol combined with gasoline is investigated in terms of brake torque, brake power, fuel consumption, thermal efficiency, volumetric efficiency, mean effective pressure, and coefficient of variation under various conditions. Second, in-cylinder pressure, mass fraction burnt, ignition delay, pressure increases, and heat release rates are also used to evaluate the combustion characteristic. Finally, the article discusses pollutant emissions such as CO, CO2, NOx, UHC, and exhaust gas temperature. Methanol, ethanol, and butanol mixed with gasoline increased fuel consumption and lowered spark-ignition engines’ thermal efficiency. When alcohol was combined with gasoline, most research found that CO, NOx, and UHC emissions were reduced due to improved combustion.

Studies on the usage of gasoline–alcohol blends as an alternative fuel in spark-ignition engines have recently gained momentum. In the present research, energy, exergy, environmental, enviroeconomic, exergoenvironmental, and exergoenviroeconomic analyses were conducted with the performance and emission values acquired by utilizing gasoline, gasoline–heptanol, and gasoline–hexanol fuels (G100, HEX5-20, and HP5-20) as a fuel under different powers at a constant speed of 1600 rpm in a single-cylinder four-stroke spark-ignition engine. As the ratio of alcohol in fuel blends increases, fuel consumption also increases. NOX emission is higher, and CO and HC emissions are lower in alcohol-based fuel blends than G100 fuel. The highest thermal efficiency is 41.09% in G100 fuel at a power of 5 kW. As the ratio of alcohol in fuel blends increases, thermal efficiency decreases. The highest exergy destruction and entropy generation were determined to be 6.25 kW and 0.02134 kW/K, respectively, in HP20 fuel at a power of 5 kW. Entropy generation increases with an increase in the ratio of alcohol in alcohol-based fuels. HEX20 and HP20 fuels produce 25% and 30% more entropy, respectively, compared to G100 fuel. The mass and financial costs of the damage caused by the CO2 emission of fuels to the environment were determined by conducting four different analyses using energy and exergy analysis data. According to the exergoenvironmental and exergoenviroeconomic analyses, HP20 fuel reached the highest environmental pollution values of 4538.19 kg CO2/month and 65.804 $/month, respectively. The environmental cost of the CO2 emission released from the exhaust to the atmosphere is higher in alcohol-based fuels than G100 fuel. As a result of all analyses, it was concluded that hexanol and heptanol could be alternative fuels in spark-ignition engines under particular conditions. [ABSTRACT FROM AUTHOR]

A large portion of urban emissions in developing countries come from old gasoline vehicles driven in metropolitan areas. The present study aimed to develop models to estimate the environmental impact of different contents of gasoline and ethanol mixtures (pure gasoline; 25, 50, 75% ethanol blended to gasoline; and 100% ethanol) in a flex-fuel engine. We tested the blended fuel using three different speeds and recorded the GHG emissions and engine output data. The data mining approach was used to develop environmental impact predictive models. The ethanol content in gasoline; the engine rotational speed 900, 2000, and 3000 rpm; and λ were used as attributes. The classification target was the environmental impact concerning the CO2 emission ("low," "average," and "high"). We employed the Random forest algorithm to develop predictive models. The mean values of CO2 concentrations for all studied fuel content were above 2.47% of the volume. The trees' models (accuracy 73%, κ =0.61) showed three alternatives for predicting the environmental impact based on the ethanol blend, the engine rotation, λ, and the air-fuel ratio. Such models might help policymakers develop educational campaigns to reduce short- and medium-term urban commuter traffic pollution in countries that lack suitable urban transportation. [ABSTRACT FROM AUTHOR]

To further understand the processes and phenomena taking place in the pre-chamber (PC) ignition concept, many studies under simplified conditions have been carried out in different experimental facilities (e.g. constant volume chambers and rapid compression machines). However limited information is provided about how the volume, orifice diameter and number of orifices were defined, raising the question whether the results are representative of engine-like conditions or not. This novel study arises from the necessity to determine a methodology to reproduce a reference pre-chamber, preserving as much as possible its jet characteristics. A theoretical development based on the first law of thermodynamics has been performed, and a relationship between the effective flow area, pre-chamber volume and engine speed is proposed as the governing parameter of the mass exchange between chambers. Besides, relaying on the know-how of gas jets, a relationship between the orifice diameter, jet tip penetration and engine speed is suggested as the criterion to preserve the relative jet penetration (respect to the distance from the PC hole to the combustion chamber walls). A numerical validation of these assumptions was carried out using a one-dimensional flow calculator to estimate the thermodynamic properties and mass transfer between chambers, and a one-dimensional spray model to estimate the penetration of the PC combustion products jets. Finally, preserving the ratio between the total area of the PC holes and the product of the PC volume and the engine speed for two pre-chamber geometries, an identical pressure rise rate, in an angular basis, is achieved in both pre-chambers. Furthermore, the same relative jet penetration rate, in an angular basis, can be also achieved, even under different engine speeds, when the ratio between the orifice diameter and the product of the square of the jet free length and the engine speed is preserved. [ABSTRACT FROM AUTHOR]

Along with industrialization and transportation, the higher living standard is also the main reason for the increase in energy demand. This increasing energy demand motivates researchers to find new alternative fuels that are eco-friendly and sustainable. In this concern, to analyze the performance, emissions, and combustion characteristics of an SI engine fueled by petrol-acetylene under DF mode is the main purpose of this study. For this purpose, a VCR spark ignition engine was used and operated at the engine maximum speed (1800 rpm). The experimental study was carried out at different acetylene gas flow rates and spark timing.In this study, the acetylene gas flow rate was first optimized on a performance basis. Furthermore, the engine was run at an optimized acetylene gas flow rate (100 LPH) to find out the optimum value of spark timing. In further experimentation, it is also found that the BThE to be maximum and emissions were significantly low or comparable at spark timing 20º CA bTDC (at 100 LPH) as compared to other spark timing and baseline case at all loads. The effects of NOx and smoke are not considerable. Hence, it is not covered in this study. The heat release rate and peak cylinder pressure are found to increase with the advancement of spark timing. But knocking was observed at higher spark advance. [ABSTRACT FROM AUTHOR]