为了研究带有无叶扩压器的离心压气机内部的非稳定流动特征，针对某离心压气机的非定常数值模拟结果，通过本征正交分解 (POD) 法分析小流量工况下无叶扩压器内部的非稳定流动.研究结果表明：无叶扩压器的内部流场主要受上游叶轮及下游蜗壳的影响；POD法成功地捕捉到了叶片扫描频率所对应的射流-尾迹结构以及低频率的非稳定流动模态；非稳定模态的特征频率为22104Hz，周向存在多个扰动，并且该扰动以径向波动为主，在周向并不传播；非稳定模态的重构结果可以直观地展示失稳流动的发展过程；流场快照的采样频率对POD法所获得的结果有所影响.
To investigate the unstable flow characteristics inside the centrifugal compressor with a vaneless diffuser, the proper orthogonal decomposition (POD) method was applied to the unsteady numerical simulation results to analyze the unsteady flow inside the vaneless diffuser under small flow conditions. The results indicate that the fluid field of vaneless diffuser is mainly influenced by the upstream blades and the downstream volute. In addition, POD method is capable of capturing the jet-wake flow structure, of which the characteristic frequency equals the blade passing frequency, as well as the unstable mode with low frequency. The characteristic frequency of the unstable mode is 22104Hz, and there exists several perturbations in different circumferential positions. These perturbations are mainly radial fluctuation but do not propagate in the circumferential direction. The reconstruction result of the unstable mode can visually show the development of the corresponding unstable flow. The sampling frequency of the flow field snapshots has an effect on the result of POD method.
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