Experimental investigation on stall characteristics of contra-rotating compressor with variable speed ratios

Abstract

By experiment at a low-speed large-scale axial contra-rotating compressor, the near stall points of 19 speed configurations were captured and the stall characteristics under different speed ratios were obtained successfully. The results show that the compressor with speed ratio greater than 1 are more likely to stall than the compressor with speed ratio less than 1 and the flow rate at the starting point of stall is at least 18% earlier, the pressurization capacity is at least 5.5% higher when speed values of the front and rear rotors are interchanged. At the same speed ratio, the dimensionless characteristic lines of pressure rise coefficient-flow coefficient almost coincide. With the decrease of speed ratio, the dimensionless characteristic line of contra-compressor moves upward. Through summing up all speed configurations' stall types and stall initial disturbance frequency, it can be found that: there is a critical speed ratio between 1.125 and 1.167 in the contra-rotating compressor studied in this paper. When the speed ratio is less than the critical value, the stall disturbance has the characteristic like spike stall. At this time, the initial stall disturbance frequency is higher with the speed ratio is smaller. And at the same speed ratio, the initial stall disturbance frequency increases with the increase of the average speed of the front and rear rotors. When the speed ratio is greater than the critical value, the stall disturbance doesn't rotate circumferentially.