To investigate the relationship between aerodynamic rotating instability and fluctuated characteristics of tip clearance flow

experiment and numerical studies were conducted on a 1.5 stage low speed axial flow compressor. The rotating instability was detected through casing mounted dynamic pressure sensors. The phase-locked and root mean square(RMS) pressure contours showed that the interaction of tip clearance flow with the neighboring blade was the most likely cause of casing flow field fluctuation. From the calculated results of whole-annulus cascade

it is found that the tip clearance vortex structure oscillates periodically at low flow rate conditions. Furthermore

phase lag of pressure fluctuations exist between two neighboring passages

which induces a rotating pressure wave of multiple frequencies. The frequency characteristics of this rotating pressure wave caused by fluctuation of tip clearance flow are coincident with the frequency of rotating instability. This suggests that the fluctuation of tip clearance flow is the major contributor to the initiation of rotating instability.