小流量工况下采用孔式机匣的离心压气机内部流场分析

Analysis of Centrifugal Compressors With Holed Casing in the Small Flow Condition

实验结果表明,应用于半开式离心压气机的孔式机匣处理方式可以有效扩大压气机的稳定工作范围,而且不会降低压气机的效率。采用数值计算方法,比较了某离心压气机叶轮有无孔式机匣处理的内部流动情况,计算结果与实验结果相符。通过对小流量工况下计算结果的分析发现,孔式机匣处理结构对压气机叶片通道上部区域的流动影响显著,抽吸流量重新进入叶片通道后可以降低叶片通道入口局部的气流冲角。孔式机匣处理结构还可以抑制叶顶间隙涡,补偿抽吸掺混带来的损失。

It was demonstrated by experiments that the holed casing treatment could expand the stable working range of the centrifugal compressor with unshrouded impellers effectively without efficiency penalty. Numerical computations were adopted to study the flow fields in centrifugal compressors both with and without holed casing treatment. The numerical computation results are consistent with experimental results. Analysis on flow fields in the small flow condition shows that holes in the casing can affect the upper flow field of the impellers, reduce the flow incidence in the impeller passage inlet because of the re-adding of the suction flow. Besides, the holes can also restrain the vortexes in the compressor tip clearance leading to recompense of the loss coming from the suction and re-mixing.