| Budget Amount *help |
¥2,600,000 (Direct Cost: ¥2,600,000)
Fiscal Year 1996: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1995: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
Effects of Coriolis force, namely, stream surface inclination on turbulent flow fields in compressor rotors have been investigated by comparing experimental and computational results of the tip leakage flow in a diagonal flow rotor with those in an axial flow rotor. It was found out that "breakdown" of the tip leakage vortex occurs at the aft part of the passage in the diagonal flow rotor. The "vortex breakdown" causes significant changes in the nature of the tip leakage vortex : disappearance of the vortex core, large expansion of the vortex, and appearance of low relative velocity region in the vortex. These changes result in the following behavior of the tip leakage flow substantially different from that in the axial flow rotor :
1 Because of the disappearance of the vortex core with the concentrated vorticity, the rolling-up of the tip leakage vortex is not observed downstream of the diagonal flow rotor.
2 The disappearance of the vortex core leads to the loss of the pressure gradien
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t induced by the concentrated vorticity, so that the pressure trough vanishes from the casing wall at the aft part of the rotor passage.
3 The disappearance of the vortex core seems to results in the fact that the noise level of the diagonal flow rotor is considerably low, compared with the axial one.
4 Because of the large expansion of the leakage vortex caused by the low relative velocity region with reverse flow, the low-energy fluid due to the leakage flow is spread out from the casing to about a half of span. As a result, much larger growth of the casing wall boundary layr occurs, compared with the axial flow rotor.
5 Downstream of the diagonal flow rotor, the absolute tangential velocity increases considerably in the casing wall boundary layr, because the fluid in the low relative velocity region has a large tangential component of the absolute velocity, like the wake.
6 The large growth of the casing wall boundary layr causes large reduction of efficiency with the tip clearance : the reducing rate of efficiency is about three times as large as that of the axial flow rotor. Less
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