柴油机EGR系统文丘里管内流动数值模拟

Numerical Simulation of Flow in Venturi Tube for EGR System of Turbocharged Diesel Engine

研究了采用文丘里管引射方式的增压柴油机废气再循环(EGR)系统及结构,按照增压柴油机EGR系统工作原理,对文丘里管在不同EGR率引射情况下的内部流动进行了三维数值模拟,对文丘里管内空气与废气形成的混合气的流场状态等参数进行了分析,计算结果表明,EGR率对文丘里管压缩段前的初始压力恢复效果有较大影响,EGR率引射量越大,压力恢复效果越差,为了满足大EGR率的要求,应减小文丘里管扩压角,适当增大混合段喉口直径和EGR引射口直径以及引射口的数量。

The structure of EGR system mixer in turbocharged diesel engine in which venturi tube ejector mode is used is studied. In accordance to the principle of EGR system, a 3-dimensional internal flow in venturi tube is simulated under different guide-injected EGR rates, and the parameter of the mixture of air and EGR gas in venturi tube was analyzed. Numerical simulation results show that EGR rates have obvious effects on initial pressure recovery before compression section in venturi tube. And the more EGR gas injected is, the worse pressure recovery effect is. In order to actualize larger EGR rates, the diffuser angle of venturi tube should decrease ap- preciably, and the throat diameter of mixer section and EGR guide-injected orifices should increase properly, and the numbers of orifice in which EGR is injected should also be increased.