NUMERICAL SIMULATION OF ENDWALL FENCE ON THE SECONDARY FLOW IN COMPRESSOR CASCADE

In this paper, based on the experimental data, a detailed numerical simulation has been carried out for the compressor cascade composed of CDA blades with fences on the endwall. There are several different configurations of the endwall fences, such as length, height, and pitch-wise location for the endwall fence. The optimum lengths, height, pitch-wise or span-wise location of the fences on the cascade end walls are obtained. The process of endwall fence's controlling secondary flow in the compressor cascade mainly lies in two ways: hindering crosswise flow from pressure surface to suction surface near the endwall of the cascade; forming and developing of fence vortex, in which the fence blockage effect is more important. Endwall fences has a significant effect on the vortices distribution, in which the formation and development of fence vortex is important. Its formation has a close relationship with the strength of the crossflow at the region between the pressure surface and fence, which is mainly due to the relative airflow movement when the pressure side branch of the horseshoe vortex rolls up and lift along the fence. For the fence vortex and passage vortex have the different rotation direction, it plays an important role in decreasing the secondary flow loss, furthermore, reducing the strength of the passage vortex. In general, stronger crosswise flow induces stronger fence vortex. As height and length of the fence increased, the blockage effect is more obvious, but the additional fence losses increased at the same time. Numerical results show that the fences, with one third of height of the inlet boundary layer thickness and the length of 75 percent axial chord, are most effective when they are located 30 percent of pitch far from the pressure surface of the blade. For all the computational cases, they reduce the cascade loss furthest respectively.