SUPPRESSION OF CAVITATION SURGE OF A HELICAL INDUCER OCCURRING IN PARTIAL FLOW CONDITIONS

Abstract

Various cavitation instabilities such as rotating cavitation, cavitation surge and etc., have been serious problems in developing high-speed turbopump inducer. These instabilities should be avoided or settled for applying inducers widely in industrial fields. In the present study, the attempts to suppress the cavitation surge, which has been observed under partial flow conditions in our helical inducers, are made by installing the obstacle plates just upstream of inducer. Two kinds of obstacle plates were used; One of which is a ring-shaped axi-symmetric plate with blockage of 39 % passage at the maximum near tip region to suppress the growth of inlet back flow under partial flow conditions. The other is to block the flow axi-asymmetrically up to 69 % of flow passage and make the inlet distortion, being used to examine the suppressive effects of asymmetric inflow on the cavitation surge. In this paper, the effects of the proposed obstacle plates on the head-rise and suction performances of inducer are firstly reported. Then, the onset regions of cavitation surge with/without the obstacle plates are presented with spectrum analyses of measured wall pressures upstream and downstream of the inducer. Finally, the suppression mechanisms of those plates are discussed utilizing the high-speed video observations as well as casing pressure measurements.