Study On Mechanism Of Flow Instability And Improvement Of Centrifugal Pump

The pump consumes a lot of energy in the industry. It can make full use of limited energyand improve the economic benefit to improve the efficiency of the centrifugal pump. Althoughthe scholars at domestic and overseas have made many work in researching the centrifugal pump,the flow instability mechanism is not fully clear, due to the complexity of flow in the pump(secondary flow, vortex flow, the complex flow separation and jet-wake and so on). It remains tobe further in-depth study. In recent20years, along with the computer hardware technology, thedevelopment of numerical calculation technology, CFD method is becoming widely used in fluidmachinery. Computational fluid dynamics, usually abbreviated as CFD, is a branch of fluidmechanics that uses numerical methods and algorithms to solve and analyze problems thatinvolve fluid flows. Computers are used to perform the calculations required to simulate theinteraction of liquids and gases with surfaces defined by boundary conditions. With high-speedsupercomputers, better solutions can be achieved. In our country, the applications and researchof CFD are still in the elementary stage at present. In order to research the pump, it is necessaryto further study the CFD technology. On the basis of the researchers at domestic and overseas,some attempt and exploration is performed to predict the performance of centrifugal pump,research the field structure and analyze the flow field parameters in the centrifugal pump withCFD technology. The distributions of the energy gradient function K at various flow rates arecalculated using the data of the numerical simulation.In this paper, the main content includes the following aspects:1) calculating the whole flowfield；2) studying on internal stability in the centrifugal pump based on the method of energygradient；3) improving the centrifugal pump performance. First, a large number of relevantliteratures have been read and analyzed, to determine the governing equation of centrifugal pumpin rotation coordinate system. Then the computational domain that includes import, impeller andvolute of the centrifugal pump is obtained. Structured hexahedral cells are generated to definethe inlet zones, while tetrahedral cells are used to define the impeller and volute. Theexperimental results were compared with the numerical results from grids with different densityand turbulence models to determine the suitable grid size and turbulence model. Then the wholeflow field parameters of centrifugal pump were obtained through the calculation, within thescope of the flow rate Q/Qn=0.2~1.2, the prediction curves of efficiency, head and shaft powerare in good agreement with the experimental results. Then the flow instability in the centrifugal pump is studied using energy gradient method. Finally, the centrifugal pump is optimized basedon energy gradient method.All of the analysis in this paper demonstrates that the application of energy gradient methodin the study of internal flow in the centrifugal pump is reliable. The results of this study providewith some support to reveal the physical mechanism of complex flow in centrifugal pump. Theresults are well in agreement with the experimental results in literature.