The use of exhaust gas recirculation(EGR)is an effective way of achieving low temperature combustion(LTC)in diesel engines thereby enabling lower levels of the in-cylinder oxides of nitrogen(NOx)to be produced.In addition the fuel injection strategy used and the control of boost pressure are key aspects in attaining low NOx and soot emissions simultaneously.In the work reported in this paper,experiments were performed on an advanced testing engine platform which allows EGR,fuel injection timing and boost pressure to be precisely controlled and the influence of each parameter on the emissions to be studied independently.The results indicate that within the investigated LTC ranges,the ratio of EGR plays the most effective role in NOx reduction; the injection pressure and boost have a more modest effect on NOx emissions in general.Nevertheless,the increased injection pressure lowers the soot emission across the EGR sweep and the augmented boost reduces the soot significantly from a high soot level.It was also observed that with the high levels of the EGR,both the carbon monoxide and unburned hydrocarbon emissions increase.The effect is attributed to the reduced oxygen concentration and the lowered flame temperature.%应用废气再循环(EGR)能够降低缸内氮氧化物(NOx)生成,是实现柴油低温燃烧的一种有效方法.以同时降低NOx和碳烟为目的,恰当的喷油策略和进气增压控制则是除EGR之外的两个关键因素.该文的实验是在先进的发动机实验平台上完成的,该实验平台可以精确并单独控制这三项参数,以单独研究每一个参数对发动机排放的影响.实验结果表明:在本研究的低温燃烧范围内,应用EGR是降低NOx排放的最有效手段;然而,喷油压力和进气压力对NOx仅有轻微影响.另一方面,在不同EGR条件下,可以通过提升喷油压力来减少碳烟排放;针对高碳烟情况,提升进气压力可以有效降低碳烟峰值.但是,随EGR率的增加,由于氧气含量减少和火焰温度降低,导致较高的碳氢和一氧化碳排放.
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