Test of unsteady flow in the tip clearance of low speed axial flow compressor

The flow field in the blade tip clearance of a low-speed axial compressor rotor is measured in detail using high frequency dynamic pressure sensors. The study of the development of the unsteady flow in tip leakage when the compressor throttles to stall has been carried out by analyzing the signal characteristic. The results show that there is a stall cell in the tip clearance and it rotates along the circumferential direction by 46.5% of rotor speed when the rotor gets stalled. When the compressor throttles, a characteristic frequency band appears and it changes according to the energy transformation of unsteady pressure fluctuations in the leading edge of the blade tip. With the flow mass decreasing, tip leakage flow moves forward to the leading edge. A stall cell arises near the leading edge and extends to the trailing edge, eventually covers the whole blade chord length; under the condition of being near stall, low pressure areas in the tip clearance exhibit a “front-back” alternative distribution in channels due to the interaction of the tip leakage flow in adjacent channels. Finally, a disturbance wave forms in the circumferential direction, and its scale is about two blade channels.