涡轮增压器切换过程轴向力及其形成机理

Axial force and its formation mechanism in turbocharger switching process

针对涡轮增压器止推轴承在工况变化过程中易损坏的特点,为提高止推轴承的适应性和可靠性,以某型涡轮增压器为研究对象,建立增压器压气机与涡轮的三维模型,通过ICEM划分网格,采用CFX对压气机、涡轮流场进行数值仿真,分析涡轮增压器切换过程中轴向力的形成及其变化规律。计算结果表明:各部分轴向力在切换时刻变化最大,轴向力合力主要来源于压端,且合力方向均指向压端;压端在整个切换过程中的流动发展较为顺畅,仅在叶顶出口处产生尾迹涡流;涡端在叶根和叶片中径处均存在涡流,且在叶顶位置存在流动分离现象;不论是压端还是涡端,其轮背压力分布均存在周向不均性,且压力梯度由外向内不断减小。

Aiming at the characteristics that the thrust bearing of the turbocharger is easy to be damaged in the process of changing working conditions,in order to improve the adaptability and reliability of the thrust bearing,a certain type of turbocharger is taken as the research object,and a turbocharger compressor and turbine are established.The three-dimensional model is divided into meshes by ICEM,and CFX is used to carry out numerical simulation of the compressor and turbine flow fields,and analyze the formation and variation of the axial force during the switching process of the turbocharger.The calculation results show that:the axial force of each part changes the most at the switching time,the resultant axial force mainly comes from the pressure end,and the direction of the resultant force all points to the pressure end;the flow development of the pressure end is relatively smooth during the whole switching process,and only at the tip of the blade.The wake vortex is generated at the outlet;the vortex end exists at the blade root and the middle diameter of the blade,and there is a flow separation phenomenon at the tip;no matter it is the pressure end or the vortex end,the pressure distribution of the wheel back has a circumferential inhomogeneity,and the pressure gradient decreases from outside to inside.