喷油策略对汽油压燃颗粒物排放特性的影响

在一台单缸柴油机上研究了喷油参数(预主喷间隔角、预喷比例、主喷时刻和喷油压力等)对汽油压燃(gasoline compression ignition,GCI)颗粒物排放特性的影响。研究结果表明:喷油策略对缸内油气混合及进一步对燃烧过程的影响是其影响颗粒物排放特性的主要因素。在设定的研究工况下,随预主喷间隔角增大,积聚态颗粒数量浓度下降,但核态颗粒数量浓度基本不变,颗粒物中的核态和超细颗粒比例明显升高;增大预喷比例,核态颗粒和积聚态颗粒数量浓度均大幅降低,颗粒物中的核态和超细颗粒比例变化较小;主喷时刻提前,颗粒物数量浓度下降,平均粒径减小,数量浓度峰值向小粒径方向偏移;提高喷油压力可有效降低积聚态颗粒数量浓度,缩小缸内生成颗粒物的粒径范围,但对核态颗粒的数量浓度影响较小。

Effects of Injection Strategy on Particulate Matter Emission Characteristic in Gasoline Compression Ignition

The effects of injection parameters(pilot-main injection interval, pilot injection ratio, main injection timing and injection pressure) on the particulate matter emission characteristics of gasoline compression ignition(gasoline compression ignition, GCI) were investigated on a single cylinder diesel engine. The results show that the difference of air-fuel mixture quality and combustion process caused by the various injection parameters are the key factors that affect the particulate matter emission characteristics. Under the setting research conditions, the number concentration of accumulation mode particulate is decreased when the pilot-main injection interval is increased. However, the number concentration of nucleation mode particulate are almost the same, and the rations of nucleation mode particulate and ultra-fine particulate are obviously increased. The number concentrations of nucleation mode particulate and accumulation mode particulate are significantly reduced by increasing the pilot injection ratio, while the nucleation mode particulate and the ultra-fine particulate have almost no change. When the main injection timing is advanced, the particulate number concentration and the mean particulate number are decreased, and the peak number concentration shifts towards to smaller particulate diameter region. The number concentration of accumulation mode particulate and the average particle size can be effective reduced by elevating the injection pressure, but it has smaller impacts on the number concentration of nucleation mode particulate.