直喷式柴油机起动过程排放历程分析

柴油机冷机起动排放高于热机起动,为了分析其排放的变化历程及形成原因,利用瞬时转速及燃烧测试系统,在直喷式柴油机上进行了冷机与热机起动对比试验。试验结果表明,冷机起动整个过程中供油量较高,导致冷机起动总体排放量比热机高。冷机起动初始期失火循环和燃烧不完全循环以及过渡期滞后燃烧循环较多,导致这两个阶段的HC和CO排放明显升高。降低起动供油量,减少在起动初始期和过渡期产生的不完全燃烧和失火循环,是降低柴油机起动过程排放、进行燃烧过程优化控制的重点。

Exhaust emission histories of direct injection diesel engine during start

The exhaust emissions from the diesel engine during the cold start process are higher than those during its warm start process.The comparative test were made on a direct injection diesel engine during the cold and warm start conditions by means of an experimental system to measure the instantaneous rotating speeds and the in-cylinder pressure traces to reveal the exhaust emission histories and their formation mechanisms.The test results show that the fuel delivery is higher during the cold start process than that during the warm start process,so the total exhaust emissions are higher correspondingly.During the cold start process,the misfire and incomplete combustion cycles in the initial stage of the start process and the delayed combustion cycles in the transitional stage of the start process are more than those during the warm start process,so the HC and CO emissions during the cold start go up significantly.Thus,reducing the fuel delivery and diminishing the incomplete combustion and misfire cycles during the initial and transitional stages of the cold start process are the key measures to reduce the cold start exhaust emissions and optimize the combustion process control.