过氧化物添加剂改善HCCI发动机低负荷失火的研究

为了改善汽油HCCI发动机在低负荷的失火,通过在90号汽油中添加不同种类和不同质量的过氧化物,在一台改造过的4缸柴油机的第4缸进行HCCI燃烧试验,研究了添加剂对HCCI燃烧过程的影响。试验结果表明,在发动机转速为1 400 r/min时,使用90号汽油的HCCI发动机只能在高负荷下运行;加入过氧化物添加剂后,着火时刻提前、缸压和放热率峰值升高,燃烧向低负荷区域大幅度拓展;添加相同质量分数的不同种类过氧化物,二叔丁基过氧化物(DTBP)作用最明显。相同当量比的稳态工况下,随二叔丁基过氧化物质量分数增加,着火和燃烧放热提前、燃烧持续期缩短,失火得到有效改善,负荷范围得到拓宽。但过高的添加剂质量分数会使发动机高负荷爆震可能性增加,发动机转速为1 400 r/min下,二叔丁基过氧化物的质量分数2%左右为最佳值。

Experimental Study on the Misfire Control of HCCI Engine by Peroxide Additives at Low Loads

In order to control HCCI engine misfire at low loads,in this paper,different species and quantities of peroxide were added to 90 gasoline,and HCCI combustion tests were carried on the fourth cylinder of a modified 4-cylinder diesel engine,investigating the effects of these additives on HCCI combustion process.The experimental results showed that at engine speed of 1 400 r/min the HCCI engine could only run at high loads.With a small amount of peroxide additives in 90 gasoline,the peak values of HCCI combustion cylinder pressures and heat release rates gradually decreased,ignition timing advanced and load range is remarkably extended to lower load.For all different species of peroxide,the effect of the Di-tert-Butyl peroxide(DTBP)was the most obvious at the fixed mass fraction.At the fixed equivalence ratio,with the increase of concentration of DTBP added,the ignition and heat release brought forward,causing combustion duration decreased,misfire effectively controlled,and load range enlarged.At the large concentration,however,it resulted in more likely engine knock.The mass fraction of DTBP needs to be about 2% at engine speed of 1 400 r/min.