Comparison of Cavitation in Two Axial-Flow Water Jet Propulsion Pumps

Abstract

To investigate the appropriate design method of the water jet pump, numerical simulations are carried out to compare the cavitation in two pumps designed by the streamline method and the blade load method. Based on a brief description of the design methods, the internal flow fields and cavitation in the two axial flow water jet propulsion pumps are studied by using the SST k−ω turbulence model and barotropic law cavitation model. The cavitation location, disturbance velocity field, blade load, and their variations with the cavitation number are analyzed. The results show that the pump designed by the blade load method has a smaller cavitation bubble than the pump designed by the streamline method. With the decrease of cavitation number, the vapor bubbles first appear at the blade tip of the leading edge and then extend from the leading edge to the trailing edge. The bubble thickness and the area of the low pressure on the suction surface also increases. A whirl in the disturbance velocity is observed, which turns the direction of incoming flow to the cavitation area. Furthermore, the head drop of water jet pump is related to the decrease of blade load. The results also show that at the point of cavitation number equal to 0.319, an unexpected peak of head in the pump designed by the streamline method is observed, which indicates an unstable working point for the pump. If the priorities are anti-cavitation performance and high efficiency at the design condition, the blade load method is the first choice to design pumps. While the streamline method should be adopted if high efficiency at large flow rates is preferred.