Influence of Geometric Variations of an Inlet Cover Bleed System on Inducer Performance for an Axial Pump Operating Under Cavitating Conditions

A stability control device (SCD) is a passive inlet cover treatment that can be applied to high suction performance inducers. Significant improvements in stability have been observed when an inducer operates with an SCD, including suppression of backflow at the leading edge of the inducer at low off-design flow coefficients. This is possible because of a local increase in mass flow at the leading edge of the pump, which allows an inducer to operate with an incidence near the design point value over a wide range of flow coefficients. In this paper, the suction performance of several inducers was explored with several different SCD geometries and at different flow coefficients. Specifically, five different SCD geometries were considered to explore the influence that SCD bleed slot width and resistance to flow through the SCD channel have on inducer performance. Further, removal of tangential velocity of the energized fluid transporting through the SCD channel was considered for some scenarios to highlight the impact of swirl on inducer performance. The results reveal that for all inducers and SCD combinations considered, the most important factor affecting the mass flow through the SCD, and subsequent mass flow gain, is the inlet diffusion of the inducer. This holds for both single-phase and multiphase scenarios. Further, the cavitation number where cavitation first starts to develop in the blade throat passage of the inducer is primarily dependent on the inlet blade angle and not the SCD geometry. Consequently, the shape of the cavitation breakdown curve is largely determined by the inducer blade angle.