不同喷油压力对汽油压燃中高负荷性能试验研究

Experimental Investigation of Effect of Injection Pressure on Medium-and High-Load Performance of Gasoline Compression Ignition

基于一台改装后的压缩比为17的压燃式单缸发动机,展开不同喷油压力对汽油压燃燃烧模式发动机燃烧特性、爆震特性、效率特性和排放特性的研究,结果表明随着喷油压力的增加,缸内混合气形成速度加快,混合气着火时刻提前,燃烧持续期缩短,热效率呈现出先增大后略微降低的趋势。喷油压力的增加使得发动机爆震趋势增强,为降低最大压力升高率和爆震强度,采用推迟喷油策略,但高喷油压力下缸内燃烧对喷油时刻变得敏感,易产生较大的平均指示压力循环波动或爆震,燃烧控制难度增加。对不同喷油压力下爆震循环的缸压信号进行分析得出喷油压力对爆震频率无明显影响。喷油压力升高会使得未燃碳氢和CO排放降低,但同时也会使得NO x排放增加。

An experiment of how fuel injection pressure affects the performances of gasoline compression ignition(GCI)was conducted,including the characteristics of combustion,engine knock,thermal efficiency and emissions.It was conducted on a modified single-cylinder engine with the compression ratio of 17.The results show that with the increase in the injection pressure,the air-fuel mixture forms much more quickly,the auto-ignition timing advances towards the top dead center,and the combustion duration becomes shorter.All of those lead to a higher thermal efficiency at first and a slightly lower one later.However,high injection pressure will lead to multipoint auto-ignition,causing higher maximum pressure rise rate and severe engine knock,which requires a delayed injection timing.The combustion becomes more sensitive to injection timing as the injection pressure rises,and the higher variation in coefficient of cyclic indicates mean effective pressure or knock is more likely to appear,resulting in more difficulty in combustion control.Through data analysis,no significant effects of the injection pressure on knocking frequency is found.Besides,increased injection pressure will reduce HC and CO emissions,but result in a certain increase in NO x emissions.