分层稀燃LPG直喷发动机燃烧过程数值解析

The Simulation of the Gas Mixture and Combustion of a Liquid Phase LPG Injection Engine Coupled with Simplified Chemical Reaction Mechanism Model

简化LPG燃烧反应机理模型,将反应机理简化为包含30种组分50个化学反应的机理。将简化的反应机理导入AVL FIRE软件模拟混合气的形成,并通过外设点火文件的方法实现点火,模拟计算混合气的燃烧过程。计算了燃烧过程中混合气形成以及在不同点火时刻下燃烧放热率、缸内温度、压力随曲轴转角的变化。当设定喷油定时为60°CA BTDC时,在点火时刻,火花塞处可以形成较浓混合气,空燃比约为14.625:1;点火提前角对CO与NO的排放有一定影响,随着点火提前角的减小,CO与NO的排放量减小;于701°CA时点火,放热率峰值最大,可获得较好的燃耗特性。

The reaction mechanism model is simplified to one that contains 22 species and 42 Chemical reaction equations, with which the combustion process will be simulated by importing the simplified model into AVL FIRE and achieving ignition by connecting a ignition file outside. It shows in the pictures that, the gas mixture and the heat release rate ,the cylinder temperature and pressure under different ignition timing. It turned out that it will form a rich mixture around spark plug when setting the injection timing at 60°CA BTDC ; with the decrease of the ignition advance an- gle, the emission of CO and NO will be decreased; and it will get better burnout characteristics by setting the ignition timing at 701°CA