Experimental Study And Numerical Calculation Of Cavitating Flow In Impeller Of Axial Flow Pump

Research works in this paper are financed by the item of National Science Fund of China"study on unsteady cavitation flow in axial pump impeller".(No:50776040)The axial flow pumps are widely used in important fields of national economy such as agricultural irrigation, urban water supply, shipping industry and the south-to-north water transfer project。The axial flow pumps are the rotating machine transmiting the great current capacity fluid, which will inevitably face the problems of cavitation and cavitation erosion. The occurrence of cavitation and cavitation erosion will cause a series of problems such as changes of equipment operation performance, vibration and noise, the machine can not run normally when the problems are serious. Thus, how to improve the cavitation performance of axial flow pump is one of the important researching directions in the area of hydraulic machinery.The paper begins from studying Venturi tube cavitation flow, studying on different working conditions of cavitation flow with a high-speed camera and cavitation numerical calculation. Then we perform experimental research and cavitation numerical calculation of the model axial flow pump. The main works and conclusions are as follows:1. Design the venturi tube cavitation flow experimental table, record different working conditions of cavitation flow with a high-speed camera, analyze the characteristics of cavitation bubble. Combining configuration of cavitation region and test data, we make a detailed comparison of effects of several common turbulence model in venture tube cavitation flow calculation. Results show that RNG k-εturbulence model has obvious advantages.The study provides reference for cavitation numerical calculation in turbulence model selection.2. we get model pump's energy performance and cavitation performance curve through model axial-flow outside characteristic test. In order to validate the accuracy of cavitation numerical results, firstly, we make numerical calculation of the noncavitation flow, through numerical calculation and experimental comparison analysis, results show that predict curve and the test curve trend is basically the same with the experimental data, forecasting results are consistent with experimental values nearby the design conditions, the results lay a foundation for following work.3. Make numerical calculations on cavitation flow within model axial-flow impeller based on the full cavitation model and mixed fluid two-phase flow model. Choose different flows (0.8 Q,1.0 Q,1.2 Q) and analyze the situation of cavitation flow within the impeller when primary cavitation,critical cavitation and serious cavitation. Make comparative analysis of parameters like cavitation location,extent under different working conditions. the main conclusions are as follows:(1) Under the design flow and small flow conditions, Cavitation first occurred in local low pressure area at the back of blade leading edge which is close to the tip; Under big flow conditions, Cavitation first occurred in local low pressure area on the chord length 2/3 of the back of blade leading edge to the trailing edge which is close to the tip. (2) At the critical cavitation, cavitation area located between inlet and outlet, accounting for approximately 50% of the area of the back of the blade, the bubble gathered in the back of cavitation region; With further increasing of cavitation, cavitation region extends towards the trailing edge.