Unsteady Analysis Of Axial Flow Compressor At Near Stall Conditions

Compressor’s aerodynamic stability plays an important role in developing high performanceaero-engines. To use active control method increasing the usable stall margin of compressor, it’snecessary to capture the early flow phenomenon linked to stall. For the past decade, research hadfocused on the tip leakage flow, people found the tip leakage flow had a close relationship with therotating stall and at the near stall condition, the tip leakage flow had a obviously unsteady fluctuating.So, it has an important significance to investing the low field especially the tip region flow filed whencompressor is working at near stall condition.An experimental and numerical study were conducted to investigate a four-stage low speed axialcompressor’s flow field at near stall condition. In the experimental study, it’s found that thefrequency components has a different characteristic at near stall condition from the large massflowcondition; the CFD study shows that it’s caused by the tip leakage cortex breakdown near the bladeleading edge. From the casing pressure distribution, it’s found that the tip leakage vortex starts at anearer position to leading edge with the massflow decreases and the angle between tip leakage flowtrajectory and the blade leading edge plane decreases with the massflow decreases. The reason is thatthe blade’s maximum load position moves forward blade leading edge with the massflow decreases.An experimental study was taken to investigate the compressor’s dynamic stall processing, it’s foundthat the compressor stall with a spike wave stall inception. In the stage1,2and3, there is one stallcell; in stage4, there are two stall cells. The above findings were foundation of developing moreuseful stability enhancement technology.