Investigation of the role of non-uniform suction flow in the performance of water-jet pump

Abstract

Insufficient understanding of performance deviation between the uniform and non-uniform suction flows is a major problem encountered in the design and application of water-jet pumps. In this study, numerical investigation is conducted to illustrate the performance deviation and explain its generating mechanism. Steady simulations are performed to compare the pump performance with two different computational domains. One is a single water-jet pump under uniform inflow and the other is a complete water-jet propulsion system with non-uniform inflow. Results indicate that large non-uniformity of suction flow causes a substantial drop in the pump head. Flow details in the system are comprehensively discussed to describe the non-uniform inflow. Its primary feature is a distinct swirl distortion near the top which evolves into a circumferential vortex. Vortices and blade loadings are also explored. Consequently, the internal correlation between the non-uniform inflow and performance deviation is revealed. Due to non-uniform disturbances, a spanwise vortex shedding from the hub triggers a sharp downward peak of blade loading in the hub section. Moreover, a concentrated vortex deviates from the suction surface and induces an entire reduction in blade loading of the shroud section. These remarkable reductions in the blade loading eventually generate a head deviation.