Research On Erosion Characteristics And Cavitation Performance Of A Centrifugal Pump In Slit-laden Water

As a kind of general machinery,pumps play an important role in the development of human life and society.However,many rivers in our country contain suspended sediment particles and other impurities more or less.The internal flow of the centrifugal pump operating in silt-laden water is the complex multiphase flow and its core components of the centrifugal pump usually exist erosion problems.In slit-laden water,sand particles influence wear of hydraulic machinery and at the same time,they also affect the occurrence and evolution of cavitation.At present,based on experiment,the wear and cavitation of the centrifugal pump in silt-laden water are studied,but they have not been studied completely.Therefore,it is necessary to research the wear characteristics and cavitation performance in the centrifugal pump in the condition of silt-laden water,which lays an important foundation for the design and application of centrifugal pumps in the future.This study selects a single-stage single suction centrifugal pump with the specific speed being 196 as the research object.Based on the RNG k-? turbulent model,SIMPLE algorithm,the discrete phase model and Finnie ductile material erosion model,the wear characteristics of the centrifugal pump were studied.The cavitation performance of the centrifugal pump was studied based on Mixture model and Schnerr-Sauer cavitation model.The internal flow of the fresh water and silt-laden water in a centrifugal pump was simulated.Main results are as follows:1.Under the condition of fresh water and silt-laden water,the external characteristic curves are basically the same,and the head and efficiency of silt-laden water are both higher than that in fresh water.2.Under the condition of the same flow rate,the pressure at the inlet of impeller is lower than that in fresh water.However,the outlet pressure of the impeller in siltwater is higher than that in fresh water.For the same medium,with the increasing of flow rate,the outlet pressure of the impeller decreases gradually.3.When the sand particle's size keep certain,as the volume fraction increases,the centrifugal pump's erosion rate increases gradually and the main erosion areas are concentrated on the leading side of the blade,suction side of the blade,pressure side of the blade which is closed to the exit of the blade and the section near the volute tongue.Erosion of the leading side of the blade is the most severe area,followed by the suction side of the blade and the volute wall,pressure side of the blade and the impeller hub.With the increasing of volume fraction of the sand particles,the trajectories of sand particles tend to disorder,especially near the exit of the blade and sections near the volute tongue;with the increasing of volume fraction of sand particles,the head and efficiency decrease continuously.4.When volume fraction of sand particles is constant,the pump's erosion rate increases gradually.The pressure side of the blade is the most severe area of the erosion,followed by the leading side of the blade and the impeller hub,volute wall and suction side of blade.When sand particles' size increases,trajectories of sand particles tend to move on the pressure side of the blade and the radius of the trajectory in the spiral section increases gradually.With the increasing of sand particles' size,the head and efficiency decrease continuously.5.Under the condition of silt-laden water,the critical net positive suction head is higher than that in fresh water.Under the same pressure at the inlet of the centrifugal pump,the vapor's volume is larger than that in fresh water,and the cavitation is more serious.It shows that the existence of sand particles is more likely to decrease the cavitation performance of the centrifugal pump.6.Under the condition of fresh water and silt-laden water,the cavity's distribution is basically same in a flow passage.Vapor exists at the inlet of the suction side of the blade.With the decreasing of pressure at the inlet,the intensity of cavitation is more severe,and vapor gradually spreads along the suction side of the blade to the outlet of the blade.When cavitation develop to one certain degree,the vapor region gradually spreads to pressure side of the blade.7.Under the condition of same sand particles' size and different volume fraction of sand particles,the volume fraction of vapor in the flow passage increases when the sand particles' volume fraction increases.The higher the sand volume fraction is,the larger the critical net positive suction head is and the more serious the cavitation is.