Numerical Simulation Of Flow And Pressure Fluctuation In The Whole Passage Of A Large Water Intake Centrifugal Pump

Centrifugal pump has the advantages of simple and compact structure,high-speed operation,long service life,reliable operation and transportation of different kinds of liquid,which is widely used in agriculture,chemical industry,mining and metallurgical industry,shipbuilding and other national economic fields.However,the flow structure of centrifugal pump has many dimensions and complex shapes.In the process of operation,the impeller and static parts will produce dynamic and static interference,which will induce pressure fluctuation.In serious cases,it will further induce the noise and hydraulic vibration of centrifugal pump,which will threaten the safe and stable operation of centrifugal pump and reduce the efficiency and service life of centrifugal pump.Therefore,it is of great significance to study the internal flow characteristics and pressure fluctuation characteristics of the centrifugal pump for the safe and stable operation of the centrifugal pump.In order to study the internal flow characteristics and pressure fluctuation characteristics of centrifugal pump,this paper takes a large-scale water intake centrifugal pump as the research object,based on computational fluid dynamics,uses ANSYS CFX software and SST Turbulence model to carry out three-dimensional steady and unsteady numerical simulation of the large-scale water intake centrifugal pump in whole flow passage.In the unsteady calculation,the pressure fluctuation is monitored by setting monitoring points in each flow component.The main research results are as follows:1.By analyzing the external characteristic curve,it is found that 93.95% of the maximum efficiency of the pump occurs under the design condition,and the more deviated from the design condition,the faster the efficiency drops.2.The lowest pressure of the blade appears at the leading edge of the suction face of the blade,and the pressure gradually increases from the leading edge to the trailing edge,while the pressure distribution in the volute area is uneven;the flow velocity of the impeller increases gradually from the leading edge to the trailing edge and reaches the maximum at the outlet of the impeller,and the flow velocity at suction face is larger than the pressure face;With the increase of the flow,the pressure and velocity of the impeller and the volute increases;deviate from the design condition,the flow in the pump is unstable and the streamline becomes disordered.3.By analyzing the pressure fluctuation of each monitoring point in the flow passage components,it is found that the pressure fluctuation of the inlet section,impeller,volute and tongue has obvious periodicity in the time domain except the periodic change of the pressure at the outlet section.The frequency of pressure fluctuation in the inlet section,volute and tongue is the blade frequency and its double frequency,and there are different degrees of pressure fluctuation at low frequency.The pressure fluctuation of impeller and outlet is mainly concentrated in low frequency area,and the first main frequency of pressure fluctuation is 1 times of frequency and 0.5 times of frequency respectively.3.The operation of the pump under the condition of small flow and large flow will affect the flow stability,cause backflow and vortex,and finally cause low-frequency pressure fluctuation,enhance the phenomenon of pressure fluctuation,may induce noise and vibration,seriously affect the performance of pump,and reduce the efficiency.Therefore,it is necessary to avoid the operation of the pump under the off design condition,especially under the condition of too small flow and too large flow.