背景气密度对GDI喷雾特性的影响

Influence of Background Gas Density on GDI Spray Characteristics

在一定容燃烧弹中,采用3种不同的背景气体(He、N2、CO2),通过高速摄影技术,研究了非闪沸条件下背景气密度和燃油温度对某5孔GDI喷油器喷雾特性的影响。结果表明:背景气密度是影响喷雾坍塌的关键因素。随着背景气密度的增加,坍塌程度呈现先增强后稳定的趋势,转折点位于4 kg·m^-3左右。当背景气密度低于4 kg·m^-3时,增大背景气密度,单个油束宽度的增加使得喷雾各个油束之间的间隙减小,阻碍外部气体进入内部平衡低压区,喷雾内外压差增大,导致坍塌程度增强;当背景气密度高于4 kg·m^-3时,喷雾各油束之间的间隙消失,喷雾内外的气体交换被阻断,喷雾内外压差趋于稳定,导致坍塌程度趋于稳定。燃油温度的改变对喷雾宽度的影响较小。

In a constant volume combustion bomb,three different background gases(He,N 2,CO 2)are used to study the influence of background gas density and fuel temperature on the spray characteristics of a five-hole gasoline direct injection(GDI)injector under non-flash-boiling conditions by high-speed photography.The results show that background gas density is the key factor affecting spray collapse.With the increase of background gas density,the spray collapse shows a trend of strengthening first and then stabilizing,with the turning point around 4 kg·m-3.When the background gas density is lower than 4 kg·m^-3,the spray plumes would become wider and resultantly the gap between jets becomes narrower with the increase of background gas density,further preventing the external gas from entering the enclosed low-pressure zone.The internal and external pressure difference of spray increases,resulting in the increase of spray collapse degree.When the background gas density is higher than 4 kg·m^-3,the gap between jets disappears,and the spray external and internal gas exchange is blocked.The internal and external pressure difference of spray tends to be stable,which leads to the stability of spray collapse.The change of fuel temperature has little effect on spray width.