Numerical study on flow control mechanism of endwall fence in a high-lift turbine rotor with open separation

Abstract

The enhanced cross pressure gradient and the interference effect between secondary flow and separation bubble on the suction side make the refinement of flow organization in the endwall region a key role in improving the performance of low Reynolds number turbine stages. This influence is further amplified in high-lift turbines with open separation. The flow control method of applying endwall fence on a high-lift rotor of a low-speed turbine stage has been numerically studied. By analyzing the transformation of separation bubble on the suction surface and the development of vortices in the endwall region, the flow control mechanism of the endwall fence at low Reynolds numbers is presented. The influence of different fence design parameters on aerodynamic performance has been summarized. The research results indicate that the induced generation of fence vortex can effectively suppress passage vortex. After installing the fence, the intensification of blockage in the endwall region near the leading edge effectively delays the occurrence of laminar separation. Due to the introduction of additional endwall losses, the flow control effect of the fence mainly comes from the suppression of separation. The flow field in the endwall region and flow control effect are significantly affected by the pitchiwse position and height of the fence, while the width of the fence has a slight impact. The flow control effect can be more effectively achieved by designing the height variation of the fence reasonably. In addition, numerical results indicate that the optimized fence all exhibit good control effectiveness under different operating conditions.