催化转化器内部瞬态流动过程CFD分析

Analysis of the Transient Flow Processinthe Catalyst Convertor Based on CFD

运用计算流体力学(computational fluid dynamics,CFD)方法分析了催化转化器内部瞬态流场的变化。结果表明:沿催化转化器载体轴向,由于入口处壁面的影响及尾部发生边界层分离,在进出口处分别出现两个气流速度低峰;在载体某一截面径向方向上,气流速度和温度都呈现中央高而边缘低的分布;由于固相热导率和热容量大,催化转化器固相上的温度变化很小;在一个工作循环中,随着曲轴转角变化,由于管壁处形成的漩涡区,催化转化器中气流均匀性系数先降低后升高,而由于流动阻力的影响,压力损失先上升后下降。研究可为催化转化器设计及性能分析提供依据与参考。

The transient flow distribution ina catalytic convertor is comprehensively analyzed with employing computationalfluid dynamics.The simulationresults show that the axial flow velocity in the carrierof the catalytic converteris relativelystable,howevertwo low velocity peaks come out near the entrance and outlet of the carrier respectively,which are due to thewall effects at the front entrance and the boundary layer separation at the outlet.At one given section in the carrier,in radialthe velocity and temperature tend to decline from the center to the edge of wall.The temperature of the solid phase changeslittle due to its’high thermal conductivity and capacity.In a working cycle,the pressure drop increases first and thendecreases with the increase of crank angle due to vortex zones formed at the wall while the coefficient of uniformity is justopposite owing to flow resistance.The results above can providea favorable basis and reference for the designof catalystconverter as well as its’s performance analysis.