高功率密度柴油机的排气流通特性

Exhaust flow characteristics of diesel engine with high power density

为了分析柴油机功率密度提高后排气流动特征的变化,建立单缸柴油机一维热动力模型,对转速为3000r/min时柴油机的控制参数和热动力参数进行仿真,计算结果与试验值吻合良好。应用校准的模型分析柴油机提高功率密度对排气流动的影响。结果表明,随转速提高超临界排气持续曲轴转角明显增加,在转速为4200r/min时达128°;活塞排气指示功明显增大。排气流通面积成为影响高功率密度柴油机排气流动性能的主要因素,增大排气门喉口直径,可缩短超临界排气,减小排气指示功绝对值。为高功率密度柴油机排气系统的优化设计提供理论参考。

To investigate the exhaust flow characteristics of diesel engine in high power density （HPD） condition, 1-D thermal dynamic model for a single-cylinder diesel engine was built. The control parameters and thermal dynamic parameters with the engine speed of 3000 r/min were simulated. The results of simulation were in accordance with the experiment data. The effect of increasing power density on exhaust flow was analyzed using validated model. The results showed that the corresponding crank angle of supercritical exhaust state were obviously improved with the increase of engine speed, peaked at 128~CA in 4200 r/min condition, and the exhaust indicate power was enhanced markedly. The area of exhaust flow became the main factor affecting exhaust performance of diesel engine with high power density （HPD）. With the increase of exhaust throat diameter, the corresponding supercritical angle diminished and the absolute value of indicated exhaust power reduced. This research can provide theoretical reference for optimizing HPD diesel engine exhaust system.