EGR对柴油机低温燃烧影响的试验及仿真研究

摘要

Study on the influence law and action mechanism of EGR on the diesel low temperature combustion of four cylinder based on the engine bench test numerical simulation technology was carried out. The results of the selected three representative working conditions on NEDC cycle test show: with the increase of engine speed and load ,the achieving EGR rate is reduced, and the sensitivity of EGR on the emissions influence is increasing;when the EGR rate exceeds approximately 43%at 1 800 r/min-25.4 Nm, which can realize the low temperature of both NOx and Soot emissions reduced; under the condition of limited EGR rate, NOx and Soot emissions present the trade-off relations at 2 000 r/min-82.7 Nm and 2 400 r/min-127.2 Nm. With the increase of EGR rate, HC and CO emissions basically present first decreasing then rising trends. Comprehensively analyzing the influence of EGR on combustion, performance and emission, and considering the highest EGR rate of the four-cylinder engine achieved on the study, the sequencing optimal values of EGR rate of three working condition points are 43%, 26%, and 22%.%结合发动机台架试验及数值仿真技术研究了EGR对四缸柴油机低温燃烧的影响规律及作用机理。选定NEDC循环测试中的三个代表工况进行研究的结果表明：随着发动机转速、负荷的增加，所能达到的EGR率降低，且EGR对排放影响的敏感性增大；1800 r/min-25.4 N·m工况点，EGR率高于43%时，可实现NOx和Soot排放同时降低的低温燃烧；而2000 r/min-82.7 N·m和2400 r/min-127.2 N·m工况点，在受限的EGR率条件下，NOx与Soot排放呈现trade-off关系。 HC和CO排放随EGR率的增加基本呈现先降低后升高的趋势。综合分析EGR对燃烧、性能、排放的影响，并考虑到研究所用四缸发动机所能达到的最高EGR率，三个工况点的试验EGR率优化值依次为：43%、26%、22%。