Effects of Coriolis force on Complex Turbulent Flow Field in Compressor Rotor
Grant-in-Aid for Scientific Research (C)
|Research Institution||Kyushu University|
古川 雅人 九州大学, 工学部, 助教授 (30181449)
HARA Kazuo Kyushu University, Faculty of Engineering, Research Associate, 工学部, 助手 (00150491)
|Project Fiscal Year
1995 – 1996
Completed(Fiscal Year 1996)
|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)
|Keywords||Turbomachinery / Complex Turbulent Flow / Coriolis Force / Stream Surface Inclination / Diagonal Flow Rotor / Blade Tip Leakage Vortex / Vortex Breakdown / ターボ機械 / 複雑乱流 / コリオリ力 / 流面傾斜 / 斜流羽根車 / 翼先端漏れ渦 / 渦の崩壊 / ターボ機構 / 二次流れ|
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
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.
Research Output (5results)