柴油微引燃喷射策略对双燃料柴油机RCCI燃烧性能的影响

Impact of strategy of micro pilot diesel injecting on combustion of RCCI dual fuel engine

双燃料柴油机采用柴油微引燃天然气的RCCI(reactivity controlled compression ignition,RCCI)燃烧方式能够优化排放和经济性能。本文研究微引燃柴油采用3次喷射的方式,即预喷、主喷和尾喷分别控制预喷、主喷和尾喷的喷射始点时刻,通过仿真实验的方法研究其对柴油机缸内压力、温度、放热率和NO;生成率的影响。在预喷、主喷、尾喷喷射始点时刻保持不变、引燃柴油总量不变时,改变预喷、主喷、尾喷引燃的喷油量组合,分析其对柴油机排放和燃烧性能的影响。结果表明主喷的喷油始点时刻对其性能影响最大,主喷喷油始点越早,燃烧越晚,NO;生成率越低;当引燃油量不变前提下预喷的油量越多,燃烧中心前移,NO;排放量显著增大。

The dual fuel diesel engine,which adopts the RCCI(reactivity controlled compression ignition)combustion mode of diesel micro pilot combustion of natural gas,can optimize both the emission and the economic performance.In this study,micro pilot diesel was injected at three times,that is pre-injection,main-injection and tail injection.In this study,the three-injection method is introduced as the variables of following experiments.Controlling the start time of pre-injection,main injection and tail injection respectively,the simulating experiments are designed to observe their effects on the cylinder pressure,temperature,heat release rate and NO;generating rate of diesel engine.When the starting points of pre injection,main injection and tail injection as well as the total amount of pilot diesel remain constant,the quantity of pre injection,main injection and tail injection are changed respectively,the influence on emission and combustion performance of dual fuel diesel engine is analyzed.The results show that the starting point of the main injection has the greatest influence on its performance and the earlier the starting point of the main injection,the later the combustion,the lower the NO;generation rate.When the amount of pilot fuel remains unchanged,the more the amount of pre-injecting fuel is,the combustion center moves forward,and the NO;emission increases significantly.