NON-AXISYMMETRIC ENDWALL CONTOURING IN A LINEAR COMPRESSOR CASCADE

Modern axial compressors are designed to be highly loaded in terms of aerodynamics, which can lead to challenges of increasing the compressor efficiency. Losses associated with secondary flow effects are well known to be the major limiting factor of improving the compressor performance. In this study, non-axisymmetric endwall contouring in a linear compressor cascade was generated through the optimization process. Combined with numerical simulation, wind tunnel tests on linear cascades with flat and contoured endwall were performed with various measurement techniques at the design and off-design conditions. The simulation results show that optimal endwall design can provide 3.08% reduction of the total pressure loss at the design condition. The reduction of pressure loss obtained is mainly below 24%span with the size of the high loss region being effectively reduced. At off-design condition, the numerical benefit of the endwall contouring is found less pronounced. The discrepancy is spotted between simulation and experiments. The experimental pressure loss reduction is mainly below 18% at ADP. And the pressure loss for the CEW increases greatly at off-design condition in experiments. Flow patterns revealed by numerical simulations show that the separation on the blade surface is mitigated with focus point disappearing, and reverse flow on the endwall near the suction side corner is moved away from the blade surface. CFD analysis indicates that the altered pressure distribution on the endwall accelerates the flow at the suction side corner and moves the reverse flow core further downstream. The weakened interaction between the corner vortex and tornado-like vortex from the endwall near the suction side corner is the main control mechanism of the CEW. The performance improvement in the linear compressor is mainly gained from it.