Effect of split injection on stratified charge formation of direct injection spark ignition engines
Effect of split injection on stratified charge formation of direct injection spark ignition engines
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DOI：
10.1243/14680874jer02106
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发表时间：
2007-04
影响因子：
2.5
通讯作者：
T. Li;K. Nishida;Y. Zhang;H. Hiroyasu
中科院分区：
文献类型：
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作者：
T. Li;K. Nishida;Y. Zhang;H. Hiroyasu
采用激光吸收散射（LAS）技术，研究了在类似于直喷式火花点火（DISI）发动机压缩冲程后期的环境中，不同孔洞和质量比的劈裂喷射对喷雾和混合特性的影响。通过适当的空穴和质量比对燃油喷射过程进行分离，可以为DISI发动机分层装药形成带来一定的好处。首先，可以避免高密度液相燃料在喷雾前缘堆积的现象，并且可以看到随后液相和气相的喷雾穿透长度都缩短了。二是“可燃混合物”的径向宽度（蒸汽等效比φv在0.7≤φv≤1.3范围内）显著扩大。最后，喷雾中“过稀”（φv < 0.7）混合物的数量显著减少。这些结果被认为有助于分层精益操作，减少DISI发动机的烟雾和未燃烧碳氢化合物（UBHC）排放。此外，通过使用LIF-PIV技术分析两个脉冲喷雾和喷雾诱导的环境空气运动之间的相互作用，阐明了分裂喷射效应背后的机制。
Abstract The effects of split injection with various dwells and mass ratios on the spray and mixture characteristics in an ambient environment similar to the late stage of compression stroke in direct injection spark ignition (DISI) engines were investigated by using the laser absorption scattering (LAS) technique. Through splitting the fuel injection process with appropriate dwells and mass ratios, some benefits for the stratified charge formation of DISI engines can be achieved. First, the phenomenon of high-density liquid phase fuel piling up at the leading edge of the spray can be circumvented and the subsequent reduction in the spray penetration length for both liquid and vapour phases is seen. Second, the radial width of the ‘combustible mixture’ (equivalence ratio of vapour φv in a range of 0.7 ≤ φv ≤ 1.3) is significantly extended. Finally, the quantity of ‘over lean’ (φv < 0.7) mixture in the spray is significantly reduced. These results are believed to contribute to the stratified lean operation and the reduction in smoke and unburned hydrocarbons (UBHC) emissions of DISI engines. Further, the mechanism behind these effects of the split injection was clarified by analysing the interactions between the two pulsed sprays and the spray-induced ambient air motion using the LIF-PIV technique.