【摘要】 针对重载柴油机实现高效清洁燃烧进行了燃烧控制策略的研究.实验在一台拥有高压共轨系统、废气再循环系统、可变增压系统以及推迟进气门关闭定时系统的单缸实验发动机上进行.实验结果表明,当平均指示压力低于1.1,MPa时可以采用高EGR率的低温燃烧策略.其中,基于不同负荷工况高效清洁燃烧,需要配合进气增压、推迟进气门关闭定时技术以及不同的喷油模式.在低负荷工况下,单次早喷模式及高EGR率可以实现高的热效率以及低的NOx与碳烟排放.在中负荷工况下,采用多脉冲喷射模式及高EGR率协同作用,在降低化学反应速率的同时增强了混合,避免了因为局部不均匀而导致的碳烟排放过高.高的增压度提高了缸内充量密度,有效降低了NOx、碳烟、CO及HC排放,提高了热效率.研究结果还显示,在推迟进气门关闭定时系统的帮助下,采用多脉冲喷射以及高的增压压力,可以在保持高的热效率的同时进一步降低NOx以及碳烟排放.更多还原

【Abstract】 Combustion control strategy for high efficiency and low emissions in a heavy duty diesel engine was investigated experimentally in a single cylinder test engine with a common rail fuel system,EGR(exhaust gas recirculation)system,boost system and retarded intake valve closing timing actuator.For the operation loads of indicated mean effective pressure less than 1.1,MPal,ow temperature combustion with high EGR ratio was applied.The fuel injection modes of either single injection or multi-pulse injection,boost pressure and retarded intake valve closing timing were also coupled with the engine operation condition loads for high efficiency and low emissions.At low load,single early injection mode with high EGR ratio could achieve high indicated thermal efficiency and low NOx and soot emissions.At middle load,multi-injection mode coupled with high EGR ratio lowered the chemical reaction rate and enhanced fuel/air mixability,thus avoiding non-homogeneous locality which would cause high soot emissions.High boost pressure increased the charge density in cylinder,which improved NOx,soot,CO and HC emissions and thermal efficiency effectively.The results also showed that using multi-pulse injections with the help of retarded intake valve closing timing and high boost pressure could further reduce NOx and soot emissions and meanwhile maintain high thermal efficiency.更多还原