排气门开启角度对内燃机换气过程的影响规律研究

Influence of Exhaust Valve Opening Timing on Gas Exchange Process in Internal Combustion Engine

应用模拟仿真方法和发动机试验方法,研究了某发动机在高转速外特性工况下,排气门早开角对发动机性能的作用机制和影响规律。计算和试验结果表明:排气门早开角太大虽能减小泵气损失,但同时导致有效膨胀功减小;排气门早开角太小将导致泵气损失大幅增加,对平均有效压力等动力性指标的提升不利。最佳排气门早开角的选取原则为超临界排气结束时刻在排气下止点前10°CA达到。针对原型机进行了排气门早开角的仿真优化。优化后平均有效压力提高1.3%;平均泵气有效压力和排气总损失分别降低35.4%和37%。

The effect of exhaust valve opening advance angle （EVOAA） on high speed condition points on engine full load speed characteristics was analyzed by using 1D simulation and experiments. Results show that too large EVOAA causes pumping loss and effective expand work decreasing, while too small EVOAA makes pumping loss increasing much more. The best EVOAA should be determined to make supercritical exhaust process ending at 10℃A before exhaust BDC. The objective diesel engine EVOAA is optimized, realizing BMEP increase by 1.3%, mean effective pumping pressure decrease by 35.4% and total exhaust loss decrease by 37%.