进气压力和进气温度对低负荷火花辅助汽油压燃的影响

Effects of Intake Pressure and Intake Temperature on Spark Assisted Gasoline Compression Ignition at Low Load

在一台由6缸重型柴油机改造而成的单缸试验机上,研究了进气压力及进气温度对低负荷火花辅助汽油压燃的影响。研究结果表明,各进气压力下喷油与点火正时都需保持合理间隔才能实现稳定燃烧,提高进气压力后稳定燃烧的喷油正时范围变窄而点火正时范围略有扩大;随进气压力提高,火焰传播放热速率降低,自燃放热比例增加,最大压升率减小;提高进气压力后指示热效率提高,在35 mg循环油量下,最大指示热效率从自然吸气下的41.8%提高至140 kPa进气压力的44.4%。适当提高进气温度可以提高缸内热氛围和燃烧稳定性,在保持最大指示热效率基本不变的同时拓宽稳定燃烧的喷油正时区域,但高的进气温度加快了火焰传播速度,在点火正时较早时会导致压升率过高。

The effects of intake pressure and intake temperature on spark assisted gasoline compression ignition under low load were studied on a single-cylinder testing machine transformed from a six-cylinder heavyduty diesel engine.The results illustrate that reasonable intervals between fuel injection and ignition timing must be maintained at each intake pressure to achieve stable combustion.While the intake pressure is increased,the fuel injection timing area becomes narrower and the ignition timing area expands.The increase of intake pressure reduces the flame propagation speed and mitigates maximum pressure rise rate,and the proportion of auto-ignition heat release has increased significantly.The indicated thermal efficiency increases with the increase of intake pressure.The maximum indicated thermal efficiency has been increased from 41.8% under natural aspiration condition to 44.4% with the cyclic fuel mass of 35 mg at 140 kPa intake pressure.Properly increasing intake temperature can enhance the thermal atmosphere in the cylinder,significantly improve the combustion stability while the maximum indicated thermal efficiency is the same,and expand the fuel injection timing area for stable combustion.Also,higher intake temperature accelerates the flame propagation speed,but the earlier ignition timing may cause too high pressure rise rate.