燃用直喷汽油-预混醇混合气的汽油机燃烧特性

摘要

通过进气道喷射乙醇/正丁醇方式形成预混醇混合气,通过缸内直喷汽油方式形成分层汽油混合气,研究了相同循环供油总能量下汽油机的燃烧与排放特性.结果表明,在进气过程直喷汽油时,汽油机的平均指示有效压力和指示热效率均高于在压缩过程中直喷汽油时的值,并且前者的碳氢化合物和一氧化碳排放更低.在进气过程中直喷汽油时,进气道喷醇-直喷汽油方式与仅采用进气道喷醇方式下汽油机的指示热效率相近.进气道喷乙醇-直喷汽油(E-GDI)和进气道喷正丁醇-直喷汽油(B-GDI)混合气形成方式下汽油机的效率与排放优于仅采用汽油直喷(GDI)形成混合气方式下的值,而且E-GDI方式下汽油机的指示热效率最高.直喷汽油压力对汽油机燃烧的影响与汽油直喷时刻有关.汽油直喷时刻越早,它对汽油机平均指示有效压力的影响越小.%Premixed ethanol-butanol-air mixture and stratified gasoline-air mixture were formed by ethanol -butanol port injection and gasoline direct injection,respectively,and the combustion and emission characteristics of a gasoline engine were investigated under the same fueling energy in a cycle.The results show that gasoline injection timing during the intake stroke results in higher indicated mean effective pressure(IMEP),higher ther-mal efficiency and lower carbon monoxide and hydro-carbon emissions than those during the compression stroke.When gasoline injection timing is during the intake stroke,the indicated thermal efficiency of the engine in the case of alcohol port injection-gasoline direct injection is similar to that when only alcohol is used by port fuel injection.In the case of ethanol port injection-gasoline direct injection(E-GDI)and n-butanol port injection-gasoline direct injection(B-GDI),the thermal efficiency and emissions of the gasoline engine are better than those in the case when only gasoline direct injection(GDI)is employed,and the maximum indicated thermal efficiency occurs in the case of E-GDI.The effect of gasoline injection pressure on the combustion of gasoline engine is re-lated to gasoline direct injection timing.Earlier gasoline direct injection timing has a slight influence on the IMEP of the gasoline engine.