In order to control and suppress pe

In order to control and suppress performance curve instability characterized by the positiveslope of head-capacity curve of a mixed flow pump, a very simple passive method utilizing shallow grooves mounted on a casing wall parallel to the pressure gradient(J-groove) is proposed. The optimum groove dimension and location for suppressing such an instability are determined experimentally. Results show that shallow grooves of adequate dimension and proper location can suppress such instability perfectly without decreasing the pump maximum efficiency. The remarkable effect of shallow grooves is to decrease both the swirl strength and the propagation of reverse flow at the impeller inlet region, through angular momentum absorption owing to mixing of groove reverse flow and swirl flow, yielding recovery of impeller theoretical head.