排气门二次开启影响汽油CAI燃烧的数值模拟

基于装置了电控液压无凸轮轴气门机构的单缸发动机,使用一维发动机循环模拟软件GT-Power与CHEMKIN软件,建立了汽油CAI发动机内部EGR的循环模拟模型。通过模拟计算,分析了排气门二次开启对内部EGR率的影响规律。模拟结果表明：当排气门二次开启角度单独变化时,随着排气门二次开启角度增大,EGR率先增加后减小。当进气门关闭角单独变化时,EGR率随着进气门关闭角的提前,呈先减小后增加的趋势。联合使用以上两种策略,可以将实现CAI燃烧的EGR范围扩大。研究结果也表明,适量的EGR有利于CAI燃烧的实现,过低或过高都将导致失火,在不同的转速下EGR率的分布也不相同。

Simulation of the Effects of Dual Exhaust Valve Opening Strategy on Gasoline CAI Combustion

Based on the gasoline engine equipped with valve powered by electronic hydraulic system,dual exhaust valve opening strategy was simulated and studied with a cycle simulation mode.The mode was built up by GT-POWER coupled with CHEMKIN.The results show that,as exhaust valve secondly closed later,the EGR ratio and the cylinder temperature at intake valve closing（IVC） increased and decreased after the peak point.With the intake valve closing delay,the EGR ratio increased firstly then decreased.The combined strategy can extend the EGR ratio.The simulation results also show that suitable EGR has advantage on achieving CAI combustion,when the EGR ration was higher or lower,the misfire happened.And,at different engine speeds,the distributions of EGR were different.