在涡轮增压柴油机模拟计算中MPC边界的处理方法研究

本文介绍一种在用特征线法计算排气管内压力波时,模件式脉冲转换器(简称MPC)边界的计算模型。该模型考虑了排气支管内气体与管壁间的传热、摩擦,管段的变截面、弯曲、非圆截面等因素,同时将弯管损失系数折合成摩擦系数。变截面支管与总管连接处的边界按普通三分支边界处理,但根据MPC结构的特点,压力损失系数不再选用固定不变的常数,而是采用经过修正的稳流试验下得到的经验公式,在这些经验公式中,压力损失系数不仅与相连的各管段间的流速比有关,同时还和支管与总管间的夹角,各管段间的截面比等因素有关。这样处理不仅计算简单,而且能较好地反映排气管内的压力波动情况。此计算模型的合理性和可靠性已被在6135ZD柴油机上获得的试验结果所证实。

A Research for Treating Method of Modular Pulse Convertor (MPC) Boundary at Simulating Calculation of a Turbocharged Diesel Engine

This paper suggests a mathematical model of boundary conditions for simulating modular pulse convertor (MPC) when characteristic method is used to calculate pressure wave in exhaust pipes. The heat transfer and friction between pipe wall and exhaust gas, variable cross-sections, curvature and non-circular section of exhaust pipes have been considered. The loss coefficient of curvature in the manifold has been taken as part of the friction coefficient. The boundary conditions of MPC are treated as a simple three - way branch.Experimental formulas for pressure loss coefficients, considering the flow velocity ratio, the section - area ratio and the angle between pipes, are used instead of constants. It makes calculation simple and more accurate. The model has been verified by means of experiments on 6135ZD engine.