Numeric Investigation Of Controlling Secondary Flow In Annual Compressor Cascade Using Endwall Fences

In this paper, a series of numeric investigation has been carried out about the application of endwall fence in annual compressor stator composed of CDA blades in order to restrain boundary separation and reduce the secondary loss. The fence is as long as and parallels to the camber of the airfoil, and the thickness of the fence is 0.5mm and this two parameters of the fence do not change during the numeric simulating, while the height and the pitchwise location of the fence changes. The optimum pitchwise location and height of the fence is found in subsonic cascade and the initial information of endwall fence affecting secondary flow in transonic cascade is obtained.In subsonic cascade, the fence which is equipped on different pitchwise location and with different height decreases secondary flow differently. The fence prevents the crosswise flow and the pressure side branch of the horseshoe vortex from moving towards the suction surface near the endwall of the cascade. With endwall fence, the passage vortex involves two vortices, P1 and P2. P1 forms between the pressure surface and the fence and P2 forms between the fence and the suction surface, these two vortices are much weaker than the passage vortex in the usual cascade. As the fence is closing to the suction surface, the blocking effect of the fence decreases gradually and vortices P2 intensifies and vortices P1 weakens. When the fence locates from the pressure surface 0.7t it restrains the growing of the pressure side branch of the horseshoe vortex and forms the fence vortex which rotates contrary to the passage vortex and so helps to restrain vortex P1 most effectively ; the higher the fence is , the more effectively it blocks the crosswise flow and the pressure side branch of the horseshoe vortex, while it brings more additional losses and do more harm to the formation of the fence vortex simultaneously. Numeric result shows that 5mm is the optimum height of the fence.Comparing with the usual cascade, no beneficial effect has gained in transonic compressor cascade using endwall fence. The fence do blocks the pressure side branch of the horseshoe vortex and forms vortices P2 between the...