Numerical Investigation On Cavitation Characteristics Of Waterjet Axial Flow Pump

Waterjet axial flow pump is the core component of the water jet propeller,and its performance plays a key role in the overall performance of the waterjet propeller.As a key component of the waterjet propulsion pump at work can easily lead to the occurrence of cavitation and cavitation,the pump will cause the thrust reduction,reduced efficiency,increased noise,will even cause the metal surface erosion of pump impeller.Therefore,it is very important to study the cavitation resistance of wateijet pump.In this paper,by using the commercial software Fluent,the numerical simulation of the cavitating flow in the axial flow pump is carried out.First of all,the development process of the impeller cavitation is studied.It is found that with the gradual decrease of the net positive suction head,the cavitation region extends to the edge of the blade outlet and the pressure surface of the adjacent blade.Followed by analysis of the flow state inside the impeller,cavitation in the wake of the water vapor mixing area of fluid flow direction of chaos,causing reverse jet flow,resulting in cavitation swirl wake.In order to explore the mechanism of cavitation induced by head drop,which leads to additional cavitation pump hydraulic loss,a direct effect is caused by cavitation flow regime change,another is the performance of cavitation pressure change indirect effect on the surface of the pump blade.Studied the cavitation performance of axial flow pump prototype in different rotational speed of water jet propulsion,found in certain flow conditions,as the speed decreases and the required net positive suction head is smaller,the cavitation specific speed is greater,the impeller cavitation volume is smaller,the better anti cavitation performance.Finally,in order to improve the cavitation resistance of the water jet pump,the influence of the main geometric parameters on the cavitation performance of the water jet axial flow pump is studied.The results show that when the tip clearance is increased,the suction surface cavitation and the cavitation at the top of the blade are intensified at the same time,and the cavitation performance of the pump will be increased.The decrease of the maximum blade thickness and the back move of maximum blade thickness,can improve the cavitation performance of waterjet axial pump;With the increase of blade angle,the cavitation region extends to the direction of the blade outlet and the blade root,and the cavitation performance of the water jet axial flow pump decreases;The positive curvature of the blade will increase the area of cavitation area,the degree of the blade's reverse curvature increases,the area of cavitation area decreases,and the cavitation performance of the pump is improved.