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The favorable physicochemical properties of kerosene have contributed to its widely application in aviation. However, knocking is more prone to take place in kerosene than in gasoline under the same conditions. This paper presents a study on the knock characteristics of a ROTAX914 engine that is fueled by kerosene. The knocking combustion process was simulated under various engine operating conditions. The effect of engine ignition timing, exhaust gas recirculation (EGR), and mixture concentration on the engine knocking combustion were studied based on a three-dimensional simulation. The results showed that engine knock could be effectively suppressed by delayed ignition timing. With increased EGR rates, knocking intensity was greatly suppressed.

The experimental study was carried out on a constant speed multi-cylinder spark ignition engine fueled with hydrogen. Exhaust gas recirculation (EGR) and water injection techniques were adopted to control combustion anomalies (backfire and knocking) and reduce NOx emission at source level. The experimental tests were conducted on the engine with varied EGR rate (0%–28% by volume) and water to hydrogen ratio (WHR) (0–9.25) at 15 kW load. It was observed from the experiments that both the strategies can control backfire effectively, but water injection can effectively control backfire compared to EGR. The water injection and EGR reduce the probability of backfire occurrence and its propagation due to the increase in the requirement of minimum ignition energy (MIE) of the charge, caused mainly due to charge dilution effect, and reduction in flame speed respectively. The NOx emission was continuously reduced with increase in EGR rate and WHR, but at higher rates (of EGR and WHR), there was an issue of stability of engine operation. It was found from the experimental results that at 25% EGR, there was 57% reduction in NOx emission without drop in brake thermal efficiency whereas, with WHR of 7.5, the NOx emission was reduced by 97% without affecting the efficiency. The salient point emerging from the study is that water injection technique can control backfire with ultra-low (near zero) NOx emission without compromising the performance of the hydrogen fueled spark ignition engine.

Turbulent jet ignition is a pre-chamber ignition system for an otherwise standard gasoline spark ignition engine. Turbulent jet ignition works by injecting chemical active turbulent jets to initiate combustion in a premixed fuel/air mixture. The main advantage of turbulent jet ignition is its ability to ignite and burn completely very lean fuel/air mixtures in the main chamber charge. This occurs with a very fast burn rate due to the widely distributed ignition sites that consume the main charge rapidly. Rapid combustion of lean mixtures leads to lower exhaust emissions due to more complete combustion at lower combustion temperature. The purpose of the paper is to study the combustion characteristics of gasoline, ethanol, and wet ethanol when operated with the pre-chamber combustion system and the ability of the pre-chamber ignition to extend the lean-burn limits of such fuels. The combustion and heat release process was analyzed and exhaust emissions measured. Results show that the effect of turbulent jet ignition system on the lean-burn limit and exhaust emissions varied with fuels. The lean limit was extended by using fueled pre-chamber furthest, to λ = 1.71 with gasoline, followed by λ = 1.77 with wet ethanol and λ = 1.9 with ethanol. NOx emissions were significantly reduced with increased lambda for each fuel under stable combustion conditions. For ethanol, at maximum lean limit lambda 1.9, the NOx emissions were almost negligible due to lower combustion temperature.

Using kerosene for an aero piston internal combustion engine can improve system safety. Constrained by the knock limit of kerosene, the indicated mean effective pressure (IMEP) of spark ignition (SI) aero piston engine using kerosene is lower than that of gasoline. In this study, an experimental study based on a four-stroke SI aero engine was carried out. The influences of water injection on the combustion process and the improvement of IMEP were evaluated. The results indicate that the knock phenomenon can be suppressed in a certain extent with an appropriate amount of water injection.

In the paper, the effect of water injection and different air/fuel ratio (AFR) on the gasoline engine performance and emissions was investigated theoretically. A four cylinder SI engine model was built using GT-Power professional software. The gasoline fuel was injected directly to the cylinder and the water was injected into the intake manifold with different mass flow rate. The calculated engine outputs were: cylinder pressure and temperature, brake torque, brake power, mean effective pressure, thermal efficiency, carbon monoxide, hydrocarbon, and nitrogen oxide emissions. The results of simulations shows that the increased water mass flow rate resulted in improved engine performance and decreased emissions compared to neat gasoline fuel. However, we found that the excessive increase of the water amount inside the cylinder resulted in deteriorated engine performance and, consequently, poorly combustion efficiency.

This paper presents an experimental study of the performance and emission characteristics of a port fuel injection spark ignition engine modified to fuel by compressed natural gas (CNG). Consequently, the original fuel supply system of the test engine was modified to flexibly run on either gasoline or CNG. The experiment was conducted to compare operating parameters of the test engine fueled by gasoline and CNG with the same air excess ratio (λ). The study results showed that when fueled by CNG, the brake power of the test engine decreases up to 19% and the brake specific energy consumption (BSEC) increases 14%. However, the exhaust emissions of the test engine fueled by CNG are enhanced dramatically. Indeed, CO2 emissions decrease up to 50%, NOx emissions decrease 20%, especially, CO and HC emissions reduce up to 90% and 96%, respectively. For the application of CNG in real-world conditions for in used vehicles, it is recommended that we have to concentrate to solve the problem related to the low power and high fuel consumption of the original engines fueled by CNG.

Experimental and numerical studies on the effect of spark ignition engine fueled with different fractions of CNG CO2 H2 blend were conducted. The results show that with the increase of CO2 fraction, the effect of vortex on the flame wrinkle is weakened, and the flame development period increases. With the increase of the volume fraction of hydrogen in the mixture, the flame development period shortens and the flame instability trend increases. With the increase of engine speed, the turbulence intensity in the cylinder increases. The different ignition positions have great influence on the development form and combustion efficiency of the flame surface. The reasonable selection of ignition position will be beneficial to optimize and improve the performance of the whole machine.

In this research, intake runner length, and valve timing are varied individually and simultaneously over a range of values to capitalize the induction pressure waves to boost volumetric efficiency. 1-D model of the stock engine built in Ricardo Wave software is validated with 90% accuracy against experimental test results. The volumetric efficiency of the engine is boosted by an average of 3.2% over the speed range of the engine when infinitely variable runner lengths are used. When only two variations in runner length are used, the volumetric efficiency has boosted by around 1.4% on average. On the other hand, when infinitely variable valve timings along with two variations in runner lengths are used, the volumetric efficiency has boosted by an average of 7.78 %. Due to the existence of two different runner lengths, the span of variations required in valve timing is reduced further optimizing the volumetric efficiency. However, to ensure feasibility of the design, manufacturing, assembly and operation, it is better to use only two valve timings. The co-presence of only two different runner lengths and two different valve-opening timings, the average boost of 5.40 % in volumetric efficiency throughout the operating speed range of the engine is encountered Refereed/Peer-reviewed

Low-carbon fuels such as bio-methane, obtained from biomass gasification consisting 96–98% of methane by volume, is a promising alternative fuel for internal-combustion engines. In the present work, methane is used as a surrogate of bio-methane for studying the engine characteristics. First, a comparative study was performed on a single-cylinder, water-cooled, variable compression ratio, spark-ignition engine operating under methane and gasoline fuels with compression ratio (CR) of 8.5:1. Subsequently, the effect of compression ratio was investigated on the performance, combustion including cycle-to-cycle combustion variations through statistical analysis, and emissions, when engine was operated over a wide load range at 8.5:1, 10:1 and 12:1 CRs under methane. It was found that the brake specific energy consumption and emissions were reduced for methane compared to gasoline at all operating loads. Results showed that when the CR was increased from 8.5:1 to 12:1 at low operating load of 5 N-m, brake specific fuel consumption was reduced by 7.2% and the average location of peak in-cylinder pressure ( θ p max ) was shifted towards the TDC, i.e. 17.4 to 13.5 CAD ATDC, with a decrease in cycle-to-cycle combustion variations. In addition, θ p max showed linear and quadratic relationships with peak in-cylinder pressure and IMEP, respectively.

The effects of hydrogen enrichment in a naturally aspirated spark ignition engine fuelled with compressed natural gas were investigated. A mixer that can control the enrichment fraction and assure homogeneity of hydrogen in CNG was used in the experiments. Hydrogen enrichment mitigates some of the inherent problem with natural gas engine by improving combustion due to its higher heating value, wider flammability limits, lower ignition energy and faster flame speed. The work aimed at analyzing effect of hydrogen enrichment between 10% and 30% by volume the on performance and emission at full load conditions across various engine speeds. Results show that hydrogen enrichment leads to gain in volumetric efficiency resulting in more power. High enrichment fraction is more favorable at low speed with respect to output power, while exhaust emissions of CO, CO2 and unburned hydrocarbons decrease with increasing fraction. The optimal engine speed to benefit from this system is 3000 rpm which showed good balance between output power and emissions. The optimal enrichment fraction will depend largely on the engine speed, loads and the intended balance between power and emissions.

To investigate effects of various compression ratios (CRs) and spark timing on characteristics of performance and emissions, a high CR six-cylinder heavy-duty compression ignition diesel engine was modified into the port fuel injection hydrogen and liquefied methane gas lean-burn heavy-duty SI engine and tested by using 13.6 and 14.0 CRs. Combination of alternative fuels, high CRs and control strategies was implemented in this study. Results indicated that the equivalent fuel consumption (EFC) dramatically decreased with increase of the hydrogen energy share. Additionally, the EFC reduced as higher CR was adopted. The brake thermal efficiency (BTE) firstly increased and then declined with increase of the hydrogen energy share. Besides, the BTE increased with CR. The maximum additional 1.8% of BTE was obtained by employing higher CR (14.0) for a specific operating condition. Furthermore, the NOX emissions remarkably ascended while the HC emissions significantly declined with increase of the hydrogen energy share. The CO emission formation did not show a strong relationship with the hydrogen energy share and the CR. However, the CO2 emission gradually declined with increase of the percentage of hydrogen and CR.

The direct-injection concept in gasoline engines induces emission problems due to wall impingement of fuel and lack of mixing time, compared to port-fuel-injection engines. One of the solutions for these problems is optimization of the spray pattern. In this study, injector nozzle arrangement and injection timing were optimized under the wide-open-throttle condition using computational fluid dynamics. An injection pressure of 33 MPa was utilized. Mixture homogeneity, turbulent kinetic energy, and fuel film mass were monitored to evaluate the intermediate optimal design. These variables comprise the objective function. The nozzle arrangement was restricted to consider the processability and reduce computational costs. The KIVA-3V release 2 code was combined with the optimization tool. Depending on the design, the amount of leaking along the outflow to the intake port at the end of the intake process varies, however the injection quantity was maintained for simplification of optimization process. After optimization, the vapor fuel mass fraction in the intake port was considered to form a stoichiometric mixture, and mixture formation and combustion processes were analyzed. The optimal design had a narrower pattern than the reference design and targeted the downward direction when mounted on the engine because it is easy to increase in-cylinder turbulence intensity. The optimal design showed that the mixture homogeneity increased by 0.86% based on homogeneity index and the fuel film mass decreased by 51%, while the turbulent kinetic energy showed no significant change. The exhaust emissions (carbon monoxide, hydrocarbon, soot, nitrogen oxide) were reduced, while the indicated mean effective pressure remained constant.

This study systematically investigated the application of a turbocharger system to a hydrogen spark ignition engine to extend operating limitations under high loads. The exhaust system of a commercial 2.4-L natural aspiration spark ignition engine was modified by adopting a turbocharger system. Engine test speeds were 2000–6000 rpm at intervals of 1000 rpm. The intake pressure was fixed for each experimental case, however, the quantity of hydrogen and spark advance timings were varied before the back-fire occurred. High load conditions under natural aspiration and turbocharging conditions were compared. The results indicated that distinctly higher boosts with the turbocharging system helped extend high load conditions, however, the high exhaust pressure obstructed the increasingly high load conditions under high speeds.

Evaporation of sprays and mixture formation as injection of pre-blended gasoline–ethanol mixture and as separate injection of the fuels are investigated by means of numerical simulation. Effects of operating conditions and different configurations of injection systems have been examined. Under the same operating conditions, pure gasoline mostly evaporated during the injection period, while pure ethanol evaporated mainly during the compression process. Charge temperature in the cylinder for pure ethanol is ∼60°C lower than that for pure gasoline at the end of the compression process. Independently from injection system, the dual injection results in a higher evaporation rate compared to pre-blended injection. Whether pre-blended injection or dual injection is employed, the evaporation rate is improved for port injection (PI) compared to direct injection (DI). Besides, vapour concentration at the end of the compression process of PI increases with a shift from a single-inlet manifold to double-inlet manifolds. Mixture homogeneity is enhanced with increasing ambience temperature or/and an increasing engine speed with pre-blended injection, while a strong stratified charge mixture is achieved with dual injection using double-inlet manifolds or with DI of ethanol combined with PI of gasoline.

Heavy-duty diesel engines can convert to lean-burn natural-gas spark-ignition operation through the addition of a gas injector in the intake manifold and of a spark plug in place of the diesel injector to initiate and control combustion. However, the combustion phenomena in such converted engines usually consist of two distinct stages: a fast-burning stage inside the piston bowl followed by a slow-burning stage inside the squish area. This study used flame luminosity data and in-cylinder pressure measurements to analyze flame propagation inside a bowl-in-piston geometry. The experimental results showed a low coefficient of variation and standard deviation of peak cylinder pressure, moderate rate of pressure rise, and no knocking for the lean-burn (equivalence ratio 0.66), low-speed (900 r/min), and medium-load (6.6 bar IMEP) operating condition. Flame inception had a strong effect on the flame expansion velocity, which increased fast once the flame kernel established, but it reduced near the bowl edge and the entrance of the narrow squish region. However, the burn inside the bowl was very fast. In addition, the long duration of burn inside the squish indicated a much lower flame propagation speed for the outside-the-bowl combustion, which contributed to a long decreasing tail in the apparent heat release rate. Furthermore, cycles with fast flame inception and fast burn inside the bowl had a similar end of combustion with cycles with delayed flame inception and then a retarded burn inside the bowl, which indicated that the combustion inside the squish region determined the combustion duration. Overall, the results suggested that the spark event, the flame development inside the piston bowl, and the start of the second combustion stage affected the phasing and duration of the two combustion stages, which (subsequently) can affect engine efficiency and emissions of diesel engines converted to a lean-burn natural-gas spark-ignition operation.

An experimental study was performed to investigate lubricant oil induced pre-ignition and knocking combustion process in a single cylinder spark ignition (SI) engine with full bore overhead optical access. Lubricant oil was deliberately injected to the exhaust area through a specially modified direct injector to trigger the stochastic pre-ignition in a premixed air and fuel mixture. Simultaneous heat release analysis and high speed combustion imaging were used to study the pre-ignition and combustion processes. Outlier detection based on robust statistical methods was validated as an effective and efficient approach to identify sporadic pre-ignition. When pre-ignition occurred, the pre-ignited flame-front exhibited much faster propagating speed than that of the normal spark-ignited flame-front in the first stage of flame development. In several cycles, pre-ignition was followed by the pre-ignited propagating flame-front and then a separate spark-ignited flame-front before they subsequently merged together. In a few other cycles, pre-ignition led to heavy knocking combustion caused either by the auto-ignition close to the flame-front or near the cylinder wall, or both. The ultimate knock intensity of such cycles was determined by the timing, size, and location of end-gas auto-ignition of the unburned gas. Furthermore, optical detection of the oil droplet entrained combustion in the cycle subsequent to the knocking combustion cycle implied that high frequency oscillation pressure waves ejected lubricant from the piston-ring crevice.

PREMIER (PREmixed Mixture Ignition in the End-gas Region) combustion occurs with auto-ignition in the end-gas region when the main combustion flame propagation is nearly finished. Auto-ignition is triggered by the increases in pressure and temperature induced by the main combustion flame. Similarly to engine knocking, heat is released in two stages when engines undergo this type of combustion. This pattern of heat release does not occur during normal combustion. However, engine knocking induces pressure oscillations that cause fatal damage to engines, whereas PREMIER combustion does not. The purpose of this study was to elucidate PREMIER combustion in natural gas spark-ignition engines, and differentiate the causes of knocking and PREMIER combustion. We applied combustion visualization and in-cylinder pressure analysis using a compression–expansion machine (CEM) to investigate the auto-ignition characteristics in the end-gas region of a natural gas spark-ignition engine. We occasionally observed knocking accompanied by pressure oscillations under the spark timings and initial gas conditions used to generate PREMIER combustion. No pressure oscillations were observed during normal and PREMIER combustion. Auto-ignition in the end-gas region was found to induce a secondary increase in pressure before the combustion flame reached the cylinder wall, during both knocking and PREMIER combustion. The auto-ignited flame area spread faster during knocking than during PREMIER combustion. This caused a sudden pressure difference and imbalance between the flame propagation region and the end-gas region, followed by a pressure oscillation.

China is the world largest natural gas engine market, and the natural gas price has a large fluctuation range, Natural gas-diesel dual-fuel engine may be one of the options to cope with gas price fluctuations. Effect of equivalence ratio on combustion and emissions with a low compression ratio of 14.2 in a dual-fuel 6 cylinder engine was experimentally studied. Comparison between dual-fuel and spark ignition engine at stoichiometric combustion and same IMEP was conducted. Results show that the gas consumption rate decreases with the increase of equivalence ratio regardless of the strategy in nozzle parameter, exhaust gas recirculation (EGR) rate, injection parameter. Peak heat release rate and exhaust gas temperature increased, and decrease of combustion duration is obtained due to the high equivalence ratio in dual-fuel ignition mode. The gas consumption rate trend of spark ignition mode is similar to that of dual-fuel engine with the increase of equivalence ratio. Dual-fuel engine with low compression ratio of 14.2 run as spark ignition (SI) gas engine at stoichiometric ratio, but the difference lies in the combustion process. The peak heat release rate of dual-fuel engine presents higher value, while the combsution duration of dual-fuel engine is shorter, and the gas consumption rate of dual fuel engine is lower than that of SI engine.

Objectives: Performance and emissions of internal combustion (spark ignition) engine generator is investigated using the representative biogas composition from an anaerobic co-digestion mixture of various agricultural biomass wastes present in Mindanao, Philippines such as rice hull, coconut shell, cow manure as feedstock. Methods: The gases from the representative biogas composition are then fed to the 30kW engine generator and investigated the power generated, and its exhaust emissions. Findings: Results indicated that the variation of energy generated can be related to the electrical power produced from the engine unit to power the electrical appliances used at the same flow rate and pressure. At 1.4 kW electrical load and heating value of the purified biogas as 50 MJ kg-1, the consumption of biogas was observed to be the same. The engine also showed comparable efficiency ranging from 6.26% to 7.00% at 1.4 kW load. Further, the CO2 emission is observed to be 5.40% and amount of other emission pollutants are extremely few (nearly zero) using the representative biogas fuel in the engine. Thus, biogas fuel can be used directly as fuel in the spark ignition engine. Application: The biogas fuel can be used to other engines, but it requires some minor engine modifications in order to correct the compression ratio, spark ignition timing due to the slower flame speed of biogas fuel. Keywords: Biofuels, Biogas, Biomass, Engine Emissions, Engine Performance

This paper presents performance of gasoline engine under locally produced ethanol blended with gasoline. A naturally aspirated four stroke single cylinder spark ignition engine test bed was used at various engine speeds. Different proportion of ethanol-gasoline blends were tested; E0 (0% ethanol and 100% gasoline), E1 (1% ethanol and 99% gasoline), E3 (3% ethanol and 97% gasoline) and E5 (5% ethanol and 95% gasoline). Using a sample size of 100, data were collected and analysed for all the fuel samples tested at different test conditions. The result showed improved engine performance with locally produced ethanol – gasoline blends. The maximum engine performance was attained by E3 at full load throttle condition. The local ethanol-gasoline blends gave a better engine performance over pure gasoline at different test condition. In conclusion, the study proved that locally produced ethanol can be used as a substitute to highly purified ethanol as additive in gasoline.

Combustion stability, engine efficiency and emissions in a multi-cylinder spark-ignition internal combustion engines can be improved through the advanced control and optimization of individual cylinder operation. In this work, experimental and numerical analyses were carried out on a twin-cylinder turbocharged port fuel injection (PFI) spark-ignition engine to evaluate the influence of cylinder-by-cylinder variation on performance and pollutant emissions. In a first stage, experimental tests are performed on the engine at different speed/load points and exhaust gas recirculation (EGR) rates, covering operating conditions typical of Worldwide harmonized Light-duty vehicles Test Cycle (WLTC). Measurements highlighted relevant differences in combustion evolution between cylinders, mainly due to non-uniform effective in-cylinder air/fuel ratio. Experimental data are utilized to validate a one-dimensional (1D) engine model, enhanced with user-defined sub-models of turbulence, combustion, heat transfer and noxious emissions. The model shows a satisfactory accuracy in reproducing the combustion evolution in each cylinder and the temperature of exhaust gases at turbine inlet. The pollutant species (HC, CO and NOx) predicted by the model show a good agreement with the ones measured at engine exhaust. Furthermore, the impact of cylinder-by-cylinder variation on gaseous emissions is also satisfactorily reproduced. The novel contribution of present work mainly consists in the extended numerical/experimental analysis on the effects of cylinder-by-cylinder variation on performance and emissions of spark-ignition engines. The proposed numerical methodology represents a valuable tool to support the engine design and calibration, with the aim to improve both performance and emissions.

The purpose of this work was to show and elucidate the combustion characteristics of gasoline EN91 in a spark ignition engine under different ignition timing. The combustion characteristics of gasoline under different ignition timing were obtained using the kiva4 code. The numerical results obtained in kiva4 were compared with the numerical results from other researchers who used kiva3vr2 as the simulation code. For achieving this, two cases were investigated; a complete engine cycle was successfully simulated using a four valve pent - roof engine and a comparison was made with experimental results by other researchers. At a constant speed of 600 rpm, a BASF (BadischeAnilin- und Soda Fabrik) octane rating engine - single cylinder was used where ignition timing was changed in the range of 40 BTDC to 180 BTDC. The temperature and pressure combustion characteristics in kiva4 and kiva3vr2 show a percentage error of 10%. The peak and average temperature and pressure under different ignition timing from the Kiva4 code and measured experimental results shows a qualitative closeness with a percentage error of 4%. The average temperature and pressure in kiva4 were 640K and 16.48 bar while in kiva3vr2 were 600K and 14.83 bar, the peak temperature and pressure in kiva4 were 2316.3K and 21.5 bar while in kiva3vr2 were 2171.5K and 19.4 bar. The peak temperature and pressure in kiva4 at 40 BTDC was 2075.7K and 20.37 bar while at 180 BTDC was 2166.0K and 23.47bar. The peak temperature and pressure increase with increasing spark advance until the most favorable instant time is determined. Best performance was achieved when the ignition time was set to10 degrees before top dead center.

The effect of changing in air intake temperature plays an important role to the performance of spark ignition engine. Therefore, increasing or decreasing of surrounding temperature in the world nowadays will affect the performance and the quality of air especially related to spark ignition engine. Thus, this study will be conducted to determine the heated value of air intake temperature that influence engine performance and emission. Spark ignition engine also known as heat engine depends so much to the changes in temperature. This study will present the experimental result on the performance of spark ignition engine at various cooled air intake temperatures on four-stroke four-cylinder spark ignition engine. This study also investigated the level of emission released to the environment due to decrease in air intake temperature. In this study, the exhaust emissions percentage values of CO2 and HC are recorded by using Chassis Dynamometer (MD-2WD-500). The data was taken under three different gears (gear 2, 3 and 4) at varying speed (1000, 1500, 2000, 2500 and 3000 rpm) and intake temperature range (15℃~25℃). Based on the data and result recorded, decrease in temperature do increase the engine performance and also decrease the emission percentage as well.

A simulation for the analysis of the working process of two-stroke crankcase scavenged SI (spark ignition) engine is introduced. For this work, the entire work process is divided into the intake process in the carburetor, combustion process and the scavenging process. The consideration of fluid flow in the carburetor is divided into several zones according to the change in the cross-sectional area of the fluid flow. This is useful for rationally selecting the geometrical design parameters of the intake process leading to the crankcase through the air filter, carburetor, and inlet. The calculation model in the carburetor is solved numerically using a gas dynamics model. There are several methods for simulating thermodynamic processes occurring in the cylinder, but a zero-dimensional model is provided in this paper. The scavenging process in the analysis of the working process of two-stroke crankcase scavenged SI engine is a very complex thermodynamic process. In the scavenging model analysis, there are zero-dimensional scavenging model, two-zone scavenging model, and multi-zone scavenging model, but a multi-zone scavenging model is applied in this paper. In case of the multi-zone scavenging model, it is very important to determine the ratio of each zone for the accuracy of the simulation, and there is an example on it in this paper. In the two-stroke crankcase scavenged SI engine, the engine performance change according to the change of the transfer ports opening angle is explained with an example.

In this research article, the rheological behavior of ZnO-TiO2/5W30 hybrid nanolubricant is evaluated experimentally to study the suitability of using it as an effective engine lubricant. According to the results, the hybrid nanolubricant (0.1 wt%) produced shows less viscosity than the base engine oil at the selected range’s lower temperature. It will also assist in reducing the cold-start phase issues of an automotive engine. An artificial neural network (ANN) approach is used to find the best model for predicting nanolubricant samples’ viscosities of various concentrations at different temperatures (range of 25–65 °C) and shear rates. A combination of 27 ANN models was selected and trained using the Levenberg–Marquardt backpropagation algorithm. As an optimum configuration, the ANN model designed for the hybrid nanolubricant consisted of two hidden layers with 3 and 2 neurons in the first and second layers, respectively. The tan-sigmoid function activated both the layers. The best neural network model’s regression coefficient value was 0.9987 and had a mean squared error lower than 0.0002. The resulting model could predict the rheological behavior of the hybrid nanolubricant presented in this study with high accuracy.

Carbon mono oxide (CO) and un-burnt hydrocarbons (UBHC) are the exhaust emissions from petrol engine and inhaling of these emissions cause health. They also cause impact on environment. If the engine is run with alcohol, aldehydes have to be checked also. Hence control of these pollutants is an immediate effect. These emissions can be controlled by making changes in design of combustion chamber, the fuel composition and with the provision of the catalytic converter. Copper of thickness 300 microns was coated over piston crown, inside portion of cylinder liner and cylinder head of the two- stroke 2.2 kW petrol engine at the rated speed of 3000 rpm fuelled with gasohol (blend of 20% ethanol and 80% gasoline by volume) with the provision of catalytic converter with different catalysts such as sponge iron and manganese ore with air injection. The influence of parameters of mass of the catalyst, air flow rate and brake mean effective pressure of the engine on the emissions were studied. A microprocessor-based analyzer was used for the measurement of CO/UBHC in the exhaust of the engine. Aldehydes were measured by wet method. Catalytic parameters were found to show strong influence on reduction of the pollutants in the exhaust. Copper coated spark ignition engine (CCE) with gasohol operation reduced the exhaust emissions considerably when compared to conventional engine (CE) with neat gasoline operation.

Low-carbon alcohols have been universally acknowledged as an alternative to fossil fuel in the world, which is environmentally friendly and clean. In this paper, the detailed exergy and energy analysis was carried out on a turbocharged, spark-ignition (SI) engine fueled with methanol−ethanol−gasoline (GEM) under non-knock conditions. The results indicated that increasing the alcohols proportion in blends could slightly improve the exergy efficiency and thermal efficiency and increase the percentage of total irreversibility in the total exergy. The thermal efficiency and exergy efficiency increased to a maximum value and then decreased, while the proportion of total irreversibility in the total exergy increased significantly with the spark timing retarded from the earliest timing. The exergy efficiency and thermal efficiency increased as the engine load increased. Additionally, the total irreversibility increased but the proportion of total irreversibility in the total exergy presented a trend of decreasing as the engine load increased.

Engine knock determination has been conducted in various ways for spark timing calibration. In the present study, a knock classification model was developed using a machine learning algorithm. Wavelet packet decomposition (WPD) and ensemble empirical mode decomposition (EEMD) were employed for the characterization of the in-cylinder pressure signals from the experimental engine. The WPD was used to calculate 255 features from seven decomposition levels. EEMD provided total 70 features from their intrinsic mode functions (IMF). The experimental engine was operated at advanced spark timings to induce knocking under various engine speeds and load conditions. Three knock intensity metrics were employed to determine that the dataset included 4158 knock cycles out of a total of 66,000 cycles. The classification model trained with 66,000 cycles achieved an accuracy of 99.26% accuracy in the knock cycle detection. The neighborhood component analysis revealed that seven features contributed significantly to the classification. The classification model retrained with the seven significant features achieved an accuracy of 99.02%. Although the misclassification rate increased in the normal cycle detection, the feature selection decreased the model size from 253 to 8.25 MB. Finally, the compact classification model achieved an accuracy of 99.95% with the second dataset obtained at the knock borderline (KBL) timings, which validates that the model is sufficient for the KBL timing determination.

The protection of the environment and pollution control are issues of paramount importance. Researchers today are engrossed in mitigating the harmful impacts of petroleum waste on the environment. Lubricating oils, which are essential for the smooth operation of engines, are often disposed of improperly after completing their life. In the experimental work presented in this paper, deteriorated engine oil was regenerated using the acid treatment method and was reused in the engine. The comparison of the properties of reused oil, the engine’s performance, and the emissions from the engine are presented. The reuse of regenerated oil, the evaluation of performance, and emissions establish the usefulness of the regeneration of waste lubricating oil. For the used oil, total acid number (TAN), specific gravity, flash point, ash content, and kinematic viscosity changed by 60.7%, 6.7%, 4.4%, 96%, and 15.5%, respectively, compared with fresh oil. The regeneration partially restored all the lost lubricating oil properties. The performance parameters, brake power (BP), brake specific fuel consumption (BSFC), and exhaust gas temperature (EGT) improved with regenerated oil in use compared with used oil. The emissions CO and NOX contents for acid-treated oil were 9.7% and 17.3% less in comparison with used oil, respectively. Thus, regenerated oil showed improved performance and oil properties along with significantly reduced emissions when employed in an SI engine.

Research on alternative fuel development gains importance day by day with respect to environmental concerns and issues. Alternative fuel research can yield a revolution for spark ignition (SI) engines due to their being one of the widely used energy systems worldwide. However, most studies miss the environmental impact and economy of alternative fuels, while focusing on performance and emissions characteristics of different alternative fuels. The present paper aims to introduce a novel perspective to evaluate fuels environmentally and economically. For this purpose, exhaust emissions from an SI engine fueled with gasoline, liquefied petroleum gas (LPG), and hydrogen are evaluated at a constant engine speed of 1500 rpm and the same equivalence ratio of 1.0, using the emissions index, power emissions index, energy emissions index, environmental impact, environmental cost, and environmental and social impact cost. At the end of the study, hydrogen is found to be less harmful than other fuels based on its environmental and social impact cost. On the other hand, hydrogen has the highest environmental cost at each ignition timing compared to both LPG and gasoline, whereas gasoline has the best performance from the viewpoint of environmental costs. The current paper is expected to be beneficial in evaluating or comparing different fuels in different engine types to those interested in energy, thermal studies, and environmental sciences.

Lean operation is beneficial to spark-ignition engines due to the high thermal efficiency compared with conventional stoichiometric operation. Lean combustion can be significantly stabilized by the partial fuel stratification (PFS) strategy, in which a small amount of pilot injection is applied near the spark energizing timing in addition to main injections during intake. Furthermore, mixed-mode combustion, which makes use of end-gas autoignition following conventional deflagration-based combustion, can be further utilized to speed up the overall combustion. In this study, PFS-assisted mixed-mode combustion in a lean-burn direct injection spark-ignition (DISI) engine is numerically investigated using multi-cycle large eddy simulation (LES). To accurately represent the pilot injection characteristics, experimentally-derived spray morphology parameters are employed for spray modeling. A previously developed hybrid G-equation/well-stirred reactor model is extended to PFS conditions, to capture interactions of pilot injection, turbulent flame propagation and end-gas autoignition. The LES-based engine model is compared with Reynolds-averaged Navier-Stokes (RANS) based model, allowing an investigation of both mean and cycle-to-cycle variation (CCV) of combustion characteristics. Instantaneous spray and flame structures from simulations are compared with experiments. The LES-based model is finally leveraged to investigate impacts of fuel properties including heat of vaporization (HoV) and laminar flame speed (SL). It is shown that overall, the predicted mean pressure and heat release rate traces from both RANS and LES agree well with the experiment, while LES captures the CCV and the combustion phasing in the mass burned space much better than RANS. Predicted liquid fuel penetrations agree reasonably well with the experiment, both for RANS and LES. Detailed flame structures in the simulations also reveal the transition from a sooting flame to a lean premixed flame, which is consistent with experimental findings. LES is shown to capture more wrinkled and stretched flame fronts than RANS. Local sensitivity analysis further identifies the stronger combustion phasing sensitivity to SL compared with that to HoV, and the stronger sensitivity of autoignition heat release rate than deflagration. The results from this study demonstrate the high fidelity of the developed computational model based on LES, enabling future investigation of PFS-assisted mixed-mode combustion for different fuels and a wider range of operating conditions.

Methanol is a promising fuel for future spark-ignition engines. Its properties enable increased engine efficiency. Moreover, the ease with which methanol can be reformed, using waste exhaust heat, potentially offers a pathway to even higher efficiencies. The primary objective of this study was to build and validate a model for a methanol fueled direct-injection spark-ignition engine with on-board fuel reforming for future investigation and optimization. The second objective was to understand the combustion characteristics, energy losses and engine efficiency. The base engine model was developed and calibrated before adding a reformed-exhaust gas recirculation system (R-EGR). A newly developed laminar burning velocity correlation with universal dilution term was implemented into the model to predict the laminar burning velocity with the presence of hydrogen in the reforming products. At the same EGR ratio, there is a small increase in the engine efficiency with fuel reforming compared to conventional EGR. This is mainly due to the reduction of pumping work. For the R-EGR cases, around 60% of the increase in the brake efficiency is due to the reduction of pumping work. Although the increase in brake efficiency is very small, the maximum brake thermal efficiency for the R-EGR cases is higher than for the conventional EGR cases due to a significant increase in the dilution limit. With R-EGR dilution, the maximum brake thermal efficiency was found to increase by 6.9% relative to the baseline case.