高转速小流量离心叶轮流场对背压脉动的响应分析

Analysis of flow field response to back pressure pulsation in a high-speed small flow-rate centrifugal impeller

为了研究离心叶轮流场对出口背压脉动的响应特性,自行开发了基于多块结构化网格的流场分析程序。对某燃料电池离心压缩机叶轮展开背压脉动下流场响应的算例考核,计算的性能曲线与商业软件结果吻合较好,并以该叶轮为研究对象,采用数值模拟计算其内流场对下游背压脉动的响应特性。结果表明:背压脉动参数决定了流场响应的同步性和流场参数的分布特征。流场参数的波动随背压脉动幅度的增加而增大,且相对脉动幅度均超过背压脉动;流场参数的波动随背压脉动频率的增加而显著增大,且流场变化的同步性随脉动频率的增加而降低,不同背压脉动频率下极限环的形态呈显著差异,3倍频脉动条件下不同时刻的叶表压力分布呈显著差异,且加载特性发生变化。

In order to investigate the flow field response of centrifugal impeller to outlet back pressure pulsation,a flow-field analysis program for turbomachinery based on multi-block structured grids was developed independently.Firstly,the program was validated by the flow-field response of a fuel-cell centrifugal compressor impeller under back pressure pulsation.The calculated performance curves were in good agreement with the results of commercial software.Then,taking the impeller as the research object,the response characteristics of its internal flow field to the downstream back pressure pulsation were numerically simulated.The analysis of the results shows that the pulsation of back pressure determines the synchronism of flow field response and the distribution characteristics of flow field parameters.The fluctuation of flow field parameters increases with the increase of back pressure pulsation amplitude,and the relative fluctuation amplitude exceeds that of back pressure pulsation.The fluctuation of flow field parameters increases significantly with the increase of back pressure pulsation frequency,and the synchronization of flow field change decreases with the increase of pulsation frequency.The shape of limit cycle is significantly different under different back pressure pulsation frequencies.Under the condition of third harmonic fluctuation,the pressure distributions on impeller surface at different times vary significantly,and the loading patterns vary from each other.