Investigation on the Effects of Winglet Geometry in a High Loading Compressor Rotor

摘要

In order to attenuate the effects of tip leakage flow on flow stability and aerodynamic losses of transonic rotors, an effective method with the winglet around blade tip has been applied to the NASA Rotor37 in this paper Two suction-side winglets with the maximum width of 0.25 and 0.5 times of local blade tip section and two pressure-side winglets with the maximum width of 0.5 and 0.9 times of local blade tip section are designed to illustrate the fundamental impacts on flow characteristics in tip region of rotor. Pressure side winglet contributes to an increase of local static pressure near pressure side corner, but it reduces the leakage mass flow rate due to the separated bubble over the middle of blade tip which produces a better deceleration of supersonic jet in tip gap. The suction side winglet gives rise to a gradual expansion of supersonic jet over extensive blade tip and then increase of the discharge area of leakage flow over blade tip. In addition, the excessive acceleration of flow near suction side caused by the suction side winglet deteriorates the behaviour of shock wave in passage and increases the flow blockage near stall point. As winglet extends the area of blade tip, the shearing losses of leakage flow increase in new rotors with winglet, but the entropy creation arising from the mixing of leakage flow with main flow tends to be a little decrease in new rotors with pressure side winglet. In consideration of the effects of winglet on flow behaviours in rotors, the pressure side winglet benefits to attenuate the leakage flow and reduce the blockage effects in tip region, so the new rotors with pressure side winglet undergo an over 11% increase of stall margin with no penalty of efficiency. However, for the rotors with suction side winglet, both the behaviours of shock wave and leakage flow deteriorate in tip region which may lead to the occurrence of flow instability in advance.