基于两阶段燃油喷射的直喷汽油机离子电流特性的试验

基于两阶段燃油直喷的汽油机研究了首次喷油时刻、第2次喷油时刻、两阶段喷油比例以及点火时刻对起动首循环缸内燃烧离子电流特性的影响.分析了不同燃烧边界条件下直喷汽油机缸内燃烧反相离子电流峰值及其相位的变化,进而探讨了缸内压力及放热率之间的关系.此外,分析了分层燃烧直喷汽油机典型燃烧情况下的离子电流波形特征,并且对比了分层混合气和均质混合气燃烧模式下离子电流波形特征.结果表明,调整首次喷油时刻、第2次喷油时刻以及两阶段喷油比例主要是改变缸内混合气形成特性,尤其是火花塞附近的局部混合气浓度,影响了火焰传播速度,进而也影响了形成的离子电流的强弱.提前和推迟点火时刻均导致反相离子电流峰值减小.另外,4种典型的燃烧(失火、部分燃烧、伴有后燃以及正常燃烧)情况下,离子电流波形特征有着显著的差异,且反相离子电流峰值和积分信号在4种情况下依次增大,伴有后燃的情况下在做功冲程后期再次出现离子电流峰值波形.

Experimental on Ion Current Characteristics of Two-Stage Direct Injection Gasoline Engine

The effect of 1stand 2nd fuel injection timings,1st and 2nd fuel injection proportion and ignition timing on first cycle ion current characteristics at start-up in a direct injection gasoline engine with twostage injection mode was studied.The peak value and phase of anti-phase ion current were analyzed under different boundary conditions,and the correlations between ion current and in-cylinder pressure,heat release rate were made.The characteristics of ion current wave form were compared between stratified combustion and homogeneous combustion modes.Results show that adjusting the 1stand 2ndfuel injection timings,1st and 2nd fuel injection proportion affects the in-cylinder mixture formation.Especially,it affects significantly the mixture concentrations at the vicinity of spark plug and flame propagation velocity,resulting in the influence on the ion current quality.For four representative combustion modes(misfire,partial combustion,combustion with post-combustion and normal combustion)there exist obvious differences in the wave profile of ion current,and the peak value and integral signal of the anti-phase ion current increase.In addition,the wave crest appeares once again during the expansion stroke,when the post-combustion takes place.