Experimental investigation of cavity length pulsation characteristics of jet pumps during limited operation stage

Highlights: • The development tendency of cavity length of jet pumps with different area ratio during limited operation stage is studied. • The relationship between time-averaged cavity length, flow parameter and area ratio is discussed. • The cavity length pulsation of jet pumps during limited operation stage is distinguished. • The dominant frequency distribution of cavity length pulsation is discussed. • The influence of area ratio and inlet pressure on the cavity length pulsation intensity is illustrated. Experiments were conducted to investigate the cavity length pulsation characteristics in jet pumps with different area ratios during limited operation stage. Images of various cavitating flows were captured and analyzed to study the cavity length pulsation characteristics by high speed camera technology. It was found that the development tendency of time-averaged cavity length can be divided into two sections with different pulsation intensity by throat length. Further analysis indicated that the time-averaged cavity length is a function of area ratio and outlet pressure ratio independent of the inlet pressure. And the time-averaged cavity length decreases slowly and then faster with the increase of comprehensive parameters. Meanwhile, the cavity length pulsation can be decomposed into low frequency component and high frequency component. The pulsation intensity of low frequency component is relatively high during unstable limited operation stage, while it is at a low level during stable limited operation stage. Besides, smaller area ratio and inlet pressure result in larger pulsation intensity of low frequency component during unstable limited operation stage. The experimental points of high frequency component pulsation intensity collapsed around a V-shaped curve and it reached the minimum value when time-averaged cavity length is approximate to the throat length.