Automotive Science and Engineering

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Increase of environmental pollution and restricted emission legislations have forced companies to produce automobiles with lower air pollutants. In this respect, discharge of blowby gases into the environment has been prohibited and their recirculation into the combustion chamber is proposed as an alternative solution. In addition, using EGR technique to control and reduce nitrogen oxides in internal combustion engines has been quite effective. An important common feature of these two methods is the fact that improper EGR/blowby distribution leads to the increase in other pollutants and the significant engine power reduction. Therefore, the study of important factors in maldistribution of the injected gases is of great practical importance. Besides the injection position that has significant role on distribution of injected gases, it seems that other parameters such as engine speed, injection velocity and angle may affect the distribution of injected gases. In this numerical study, a new technique is used to determine the effect of these parameters on distribution of injected EGR or blowby gases into the EF7 intake manifold. Numerical calculations are performed for three injection velocities, five injection angles and three different engine speeds. It was found that recirculated gases distribution is slightly influenced by the injection angle and injection velocity, while the engine speed is the most influential factor.

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Alcohols have been used as a fuel for engines since 19th century. Among the various alcohols, ethanol and methanol are known as the most suited renewable, bio-based and ecofriendly fuel for spark-ignition (SI) engines. The most attractive properties of ethanol and methanol as an SI engine fuel are that it can be produced from renewable energy sources such as sugar, cane, cassava, many types of waste biomass materials, corn and barley. In addition, ethanol has higher evaporation heat, octane number and flammability temperature therefore it has positive influence on engine performance and reduces exhaust emissions. In this study, the effects of unleaded iso-octane, unleaded iso-octane–ethanol blend (E10) and isooctane-methanol blend (M10) on engine performance were investigated experimentally in a single cylinder four-stroke spark-ignition engine. The tests were performed by varying the throttle position, engine speed and loads. Three sets of observations were recorded at (1301 rpm, 16.8 Kg load), (1468 rpm, 15.8 Kg load) and (1544 rpm, 10 Kg load) for all tested fuels. The results of the engine test showed that IP, IMEP, Volumetric efficiency and thermal efficiency was higher for the E10 fuel and BSFC was lower. In general, most suited blend for SI engines has been specified as a blend of 10% ethanol. It was also observed that better performance was recorded during second set of observation for all the tested fuels. It was also found that ethanol–gasoline blends allow increasing compression ratio (CR) without knock occurrence.

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This study investigates the performance of Reactivity-Controlled Compression Ignition (RCCI) engines under varying engine speeds using a 4E approach (Evaporation, Energy, Emissions, Exergy) and introduces innovative multidimensional efficiency indices. A 1.9-liter TDI Volkswagen engine was modeled in CONVERGE CFD software to analyze spray dynamics, combustion processes, and emissions across different engine speeds. New indices, including Evaporation-Energy Performance Index (EvEPI), Emission-Energy Synergy Index (EmESI), and Exergy-Emission Balance Index (ExEmBI), were developed to evaluate engine performance comprehensively. Results reveal that optimal performance occurs within 1600–2200 RPM, where fuel evaporation, combustion efficiency, and exergy utilization are maximized while emissions are minimized. For instance, at 3100 RPM, EvEPI increases sharply to 9857.17 mg/ms, reflecting enhanced evaporation but also highlighting risks of non-uniform fuel-air mixing at high speeds. Conversely, EmESI for HC rises from 33.04 gr/kW.h at 1000 RPM to 284.90 gr/kW.h at 3100 RPM, indicating increased unburned hydrocarbons due to incomplete combustion. NOx emissions decrease from 11.51 gr/kW.h at 1600 RPM to 2.28 gr/kW.h at 3100 RPM, aligning with reduced combustion temperatures. Higher speeds lead to elevated HC and CO emissions due to shorter mixing times, while lower speeds increase NOx due to prolonged combustion durations. Exergy analysis shows total and second-law efficiencies peak at lower speeds, emphasizing the importance of optimizing operational parameters. These findings provide valuable insights for designing efficient, low-emission RCCI engines.