Tip Clearance Flow Analysis of Multi-stage Axial Compressor Based on Non-linear Harmonic Method
In order to explore the influence of tip clearance on the internal flow and aerodynamic performance of multistage axial compressor,a 12 stage multistage axial compressor was studied.Firstly,the compressor performance curves with nearly zero tip clearance(Cn0),design clearance(Cd),1.5 times design clearance(1.5Cd)and 2 times design clearance(2Cd)were predicted based on numerical simulation;Then,on this basis,the nonlinear harmonic method(NLH)is used to simulate the unsteady numerical calculation of different gap models;Finally,the internal flow field of the simulation results is analyzed.The results show that the tip clearance not only affects the flow characteristic curve of the compressor,but also has the best performance at a certain clearance.At the same time,there is an optimal clearance in the stable working range,that is,the optimal value of stall margin.Through the analysis of the flow field in the compressor blade tip region,the reasons for the influence of the vortex formed by the tip leakage flow on the compressor performance are clarified from the perspective of unsteady flow field.In the near zero clearance model,the tip clearance vortex is not obvious,and the blockage caused by too small clearance causes a large range of high-speed flow area on the blade suction surface.When the tip clearance is about the optimal value,the tip leakage flow inhibits the flow separation.With the in-crease of tip clearance,the size and intensity of vortices caused by tip clearance also increase,which reduces the perform-ance of compressor.
multi-stage axial compressornonlinear harmonic method(NLH)blade tip clearancetip clearance vortex
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