叶片扩压器小流量工况内部流动特性研究

The Investigation of the Flow Characteristics Inside the Vaned Diffuser at Small Flow Rate

在离心压缩机包含的部件中,叶片扩压器的恶化往往制约着整机的正常工作范围。本文针对叶片扩压器在小流量情况下内部的流动特性进行了非定常动态测量,并与数值计算进行了对比分析。结果表明,随流量减小,由叶轮扫掠引发的叶片通过扰动在扩压器段作用愈发明显,且分流叶片与主流叶片非均匀性尤为突出。同时,半无叶区至喉部性能对于叶片扩压器的非稳态过程具有决定作用。位于喉部附近吸力面区由大规模角涡分离诱发的喉部阻塞及其非定常扰动特性将直接诱发叶片前端失速团的产生。

For the components of the centrifugal compressor, the deterioration inside vaned diffuser usually restricts the regular operation of the whole machine. Aiming at investigating the flow structure inside the vaned diffuser at the small flow rate, the paper conducted the transient measurement, whose results are compared with the numerical results, to present the transient phenomena under this condition. The results point out that the blade passing disturbance from the impeller enhances prominently as the mass flow decreases, especially for the disturbances triggered by the non-uniformity between the main and splitter blades. Meanwhile, the performance of the region from the semi-vaneless to the throat appears to be critical during the process of the instability inside the vaned diffuser. It has been found that the considerable throat blockage caused by the large-scale corner separation on the suction side, combined with the blade passing disturbance, directly leads the initiation of the rotating stall cell at the front part of the diffuser.