变海拔下米勒循环对柴油机及DPF性能的影响

基于某高压共轨柴油机建立了一维热力学仿真模型,对DPF选型进行了优化,并分析了不同海拔下米勒循环对柴油机及DPF性能的影响。结果表明,选择非对称结构以及适当增加载体目数都有利于降低DPF压降,同时可降低DPF对柴油机动力性、经济性及原始排放的影响。进气门早关可以降低柴油机有效燃油消耗率,提高热效率,降低NOx排放,但会导致颗粒物排放增加;同时可降低DPF压降,提高DPF捕集效率,且随海拔升高,进气门早关的时刻越小,作用越明显。在低海拔条件下,进气门晚关策略对柴油机动力性、经济性及排放特性均影响不大;在高海拔条件下,适当增加进气门晚关时刻可以改善柴油机性能。

Effects of Miller Cycle on Diesel Engines and DPF Performance at Different Altitudes

A one-dimensional thermodynamic simulation model was established for a high pressure common-rail diesel engine, and the DPF selection was optimized. The results show that the selection of asymmetric structure and the increase of carrier number are beneficial to the reduction of DPF pressure drop, and the effect of DPF on the power performance, fuel economy and emissions of the diesel engine can be minimized.Early intake valve closing (EIVC) can reduce effective fuel consumption, improve thermal efficiency and reduce NOx emission; however, it will lead to increased particulate emission. Meanwhile, the DPF pressure drop can be reduced and DPF capture efficiency can be improved as well. With the increase of altitude, the earlier closing of the intake valve leads to more obvious results. At a low altitude, the late intake valve closure strategy has little effect on power performance, fuel economy and emissions. At a high altitude, the diesel engine performance can be improved by closing the intake valve even later.