Experiments on cavitation instability of a two-bladed turbopump inducer

The turbopump is a pressurizing system that supplies liquid propellants to the combustion chamber of a rocket engine at high pressure. As an integral component of a high-speed pumping system, the inducer used in a turbopump is forward-attached to an impeller to improve suction performance. This paper describes an experimental investigation on the flow instabilities of a two-bladed axial inducer due to cavitation. Cavitation development and its instabilities were analyzed. Asymmetric cavitation and cavitation surge were observed, and characterized by measuring the inlet pressure fluctuation for various cavitation numbers and flow coefficients. As flow coefficient decreases, the increased intensity of asymmetric cavitation was observed with an increased inception number of asymmetric cavitation. The frequency of the detected cavitation surge in the 4–10Hz range varied depending on the cavitation number. The instantaneous transition to cavitation surge appeared at the end of asymmetric cavitation as the cavitation number decreased. However, a further decrease in cavitation number resulted in the stable operation of the inducer with low values of pressure fluctuation. Finally, an intensive cavitation surge appeared after a significant amount of head loss.