高原环境对大功率柴油机起动过程影响研究

Effects of Altitude Environment on High-power Diesel Engine Starting Process

目的研究高原环境对大功率柴油机起动过程影响规律。方法针对平原和高原地区某12缸柴油机进行实车起动试验,对两种环境下柴油机起动过程转速与缸压数据进行分析,对比两种环境起动过程滞燃期变化规律,同时对两种环境起动过程喷雾特性进行仿真计算。结果发现在高原环境起动过程加速阶段更易出现滞速,甚至失火现象,两种环境下起动过程中以时间计滞燃期均在加速阶段快速下降,在过渡阶段下降平缓,在同一时刻高原环境滞燃期更大,且波动更大,最大可达0.9 ms。喷雾过程仿真结果发现,高原环境起动过程喷雾贯穿距发展更快,油束重心更接近燃烧室壁面。结论高原环境使得柴油机起动过程喷雾贯穿距增大,油束碰壁导致混合气形成质量变差,滞燃期变长,最终导致高原环境下起动过程出现滞速甚至失火等现象。

Objective To study influence rules of altitude environment on starting process of high-power diesel engine. Methods The starting process of a 12-cylinder diesel engine was tested respectively in plateau and plain to analyze the rotational speed and cylinder pressure of diesel engine in different environment. The laws on change of ignition delay pe-riod in different environment were compared and simulating calculation on spray characteristics in different environment were carried out. Results The diesel engine was prone to suffer from phenomenon such as stagnation or even misfire in altitude environment. The combustion delay period declined rapidly in accelerating stage, and declined gently in transition stage. The combustion delay period on altitude environment was longer and the volatility was bigger up to 0.9 ms than plain environment. The spray penetration on altitude environment formed faster, and the main part of spray was closer to the wall of combustion chamber. Conclusion The altitude environment makes the spray penetration in starting the engine longer. The wall impingement of spray reduces the quality of the formation of mixed gas and makes the combustion delay period longer, causing the phenomenon of stagnation and even misfire in the diesel engine starting process of the altitude environment.