Stator stall and partial clearance control of compressor
By numerical calculation of an 8-stage compressor,the characteristics and instability mechanism of marine compressor at design speed were obtained.At the same time,the first 1.5-stage of an 8-stage compressor was chosen to study the influence mechanism of the partial clearance on hub corner stall.The results showed that the flow instability mainly occurred in the hub-corner of stator at the design speed.The main reason is hub corner stall.The closed separation appeared in the comer and block the flow field.The 1.5-stage compressor result showed that the reason for compressor instability at design speed is the same as that of the 8-stage compressor.the partial clearance at different positions can widen effectively the margin.The effect of clearance was best when the clearance was in the middle.The clearance can not only increase the margin from 22.1％to 27.2％,but also cause the minimum loss at the maximum efficiency operation(from 93.9％to 93.21％).The leakage momentum caused by the clearance in other positions was not enough to eliminate the stall vortex in the hub.The optimal clearance was near the vortex core of stall vortex in the hub corner,where the leakage momentum was the maximum.
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