Influence Of Tip Clearance On Flow And Flow-induced Vibration Of Axial Compressor

Tip clearance is one of the most important factors affecting the efficiency of axial compressor.The flow structure in tip region,which determines the performance and stable working range,is highly depended on the size and shape of tip clearance.Therefore,it is important and meaningful to study the flow structure and flow-induced vibration at different tip clearance.This study is based on a 1.5 stage axial compressor.Experiment data is obtained to validate numerical simulation.Then,grid type and algorithm,which have much influence on simulation accuracy,are compared and selected carefully.Based on the analysis of flow field from many simulation cases,the mechanism is studied that how the performance and stable range are affected by tip leakage flow in design clearance size.After that,different clearance models are established,by which the performance and stall onset mechanism are compared.It is concluded that there exist a optimum clearance size,which is the result of interaction between corner separation,tip vortex flow and other secondary flow.Based on the two-way fluid-structure coupling approach,flowinduced vibration is also studied at near-stall condition.From the comparison of results from different clearance models,different vibration characters are found.For the small clearance,the vibration amplitude can be larger because of the increasing of pressure difference along blade tip.For the larger clearance,the vibration frequency can be larger because of increasing of unsteadiness in tip region.