B-17 循環流型ケーシングトリートメントが高圧力比遠心圧縮機の性能へ及ぼす影響(空力,一般講演)

概要

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Centrifugal compressors used for turbochargers need to achieve a wide operating range. A recirculation device, which consists of a bleed slot, an upstream slot and an annular cavity connecting both slots, is often applied to them. This paper discusses how the recirculation device affects the flow field in a transonic centrifugal compressor by using steady 3-D calculations. The followings are clarified. The bleed slot works in a similar way to circumferential grooves applied to axial compressors. It reduces the blade loading in the impeller tip region. And hence the velocity of tip leakage flow exiting the bleed slot becomes lower compared with that without the recirculation device. The flow through the bleed slot impinges on the tip leakage flow. It also deflects the trajectory of the tip leakage vortex. In addition to these effects, the bleed slot removes the fluid near the casing. It moves shock downstream due to the reduction of blockage. All these effects induced by the recirculation device contribute to the enhancement of the compressor operating range.
2011-07-06