汽油机连续可变进气凸轮轴相位策略的数值模拟

Numerical simulation on phasing strategy for a gasoline engine with continuously variable intake camshaft

针对486Q汽油机连续可变进气凸轮轴配气相位系统的研制,采用发动机循环模拟数值方法研究连续可变进气凸轮轴配气相位系统的相位策略。数值模拟表明486Q汽油机在高负荷中低转速工况通过进气相位提前抑制进气在气门关闭时刻向进气道的倒流可有效提高循环进气量,使中低转速工况动力输出性能提高6%～8%,其结果与随后试验测试获得进气相位变化量一致。综合考虑燃油消耗率和有害排放物生成,数值模拟中等负荷工况进气相位参数的调节优化,通过进气相位提前,示例工况缸内残余废气系数可从9%增加到20%,NO排放量低减约80%,燃油消耗率降低2%左右;通过试验测试确定中等负荷各工况进气相位最佳范围。探讨怠速低负荷工况改善燃烧稳定性、低减HC排放和改善低温起动性能的相位策略,数值模拟低负荷工况通过进气相位延迟抑制排气向进气道倒流以低减缸内残余废气量的效果;通过试验测试获取486Q汽油机怠速低负荷工况最佳相位器变化量。

Intake gasoline engine. camshaft equipped with continuously adjustable cam phasing units is applied to a 486Q Phasing strategies are researched through engine cycle simulation to achieve superior engine performance. The simulation results show that at high load and low and moderate speed of the engine,phasing adjustment can lead to 6% to 8% increase in power performance because phasing advance contributes to suppressing intake backflow at IVC （intake valve closed）. Cam phases obtained from numerical optimization have good agreement with engine test. At moderate load, cycle simulations show that phasing advance can increase residual gas coefficient from 9 % to 20%, and reduce NO emission by80%,BSFC（brake specific fuel consumption） by 2O//oo at a demonstration operation. With regard to fuel economy and emissions,adjustment and optimization of intake phasing at moderate load are further verified by engine test. At low load,technical approaches to enhance combustion stability,reduce HC emission and improve cold start are investigated. The effectiveness of suppressing exhaust backflow into intake duct by phasing retard is testified by simulation. Phasing changes at the operating condition are optimally obtained by engine test for improvement of combustion stability.