Experimental Investigation on the Development Process of Large-Scale Low-Speed Stall Disturbance in Contra-Rotating Compressor

In order to better understand the stall process of a contra-rotating compressor,the detailed characteristic and multi-channel unsteady pressure signals have been achieved by a special layout of high-frequency response pressure sensors.The array consists of thirty-one high-frequency response dynamic sensors coupled with two optical fiber sensors that were installed on the compressor casing in the direction of circumferential and chordwise of the upstream and downstream of the contra-rotating rotors.A significant hysteresis loop during the stall-recovery process of the contra-rotating compressor was captured successfully.The time series of unsteady signals when the compressor was working on the point of stall occurrence,the period of fully stall,and recovery stall were studied and discussed.Results show a large scale,and low-speed disturbance occurred abruptly at the leading-edge plane of the rear rotor and expands until it passes through both rotors.The single stall cell occupied a circumferential range of 135° and moved in the direction of the rear rotor with an 8.3%shaft speed.As the mass flow rate dropped,the stall cell speed decreases.During the stall recovery process,the rotational speed of disturbance suddenly increased from 7.5%to 18%and even increased to 47%just before the moment when flow recovered axisymmetric.Compared with the rear rotor,the front one dropped out unstable conditions earlier.