柴油机气门及EGR管路积碳问题的分析与解决

Analysis and Solution to Carbon Deposition on Diesel Engine Valves and in EGR Pipeline

某四缸增压柴油机在试验过程中出现中小负荷加速无力和发动机抖动现象,试验机拆解后发现气门盘部及EGR管路存在大量积碳。通过分析排查,发现由于配气相位不合理导致中低转速燃烧不充分,未燃烧燃油堆积在气门及EGR管路形成积碳。提出推迟配气相位方案并进行CAE分析计算。仿真结果表明,配气相位推迟,发动机充气系数增大,排气损失减小,残余废气系数减小,烟度降低。试验结果验证了仿真分析的正确性,结果表明,推迟配气相位可明显改善试验发动机中低转速时的燃烧及排放,燃油消耗率也有所下降,但高速时功率和扭矩稍有下降。

A four-cylinder TC diesel engine accelerated powerlessly and shook at middle and low load in a test. After dismantled, the engine was found to have a lot of carbon deposition on the bottom of the valve and in the EGR pipeline. Inspection and analysis were made to fine the causes. It was unreasonable cam phase that caused inadequate combustion at middle and low speed and unburnt fuel accumulated on the valve and in EGR pipeline which formed carbon deposition. Postponing cam phase was proposed and CAE analysis was performed. The outcome of the CEA analysis shows the postponed cam timing increases engine air charge coefficient and reduces exhaust loss, residual exhaust gas coefficient as well as soot. The correctness of the simulation was also verified by test and it turned out that postponing cam phase can obviously improve the combustion of the engine at the middle and low speed and reduce emissions and fuel consumption, but the power and torque at high speed will slightly decline.