Study On Flow Characteristics Of Solid-liquid Two-phase Flow In Self-priming Pump

The self-priming pump is a special centrifugal pump.Due to the existence of the gas-liquid separation chamber,the self-priming capability avoids the process of injecting water into the pump during the second start of the ordinary centrifugal pump.Therefore,self-priming pumps are widely used in situations where multiple stops are required,such as pumping domestic sewage,coal mine water delivery,and farmland irrigation.Since the self-priming pump is often applied to the complicated working environment,the medium often includes domestic garbage,cinder and gravel,so it is a typical solid-liquid two-phase flow.The impact of solid phase particles in the medium cause serious erosion damage,which greatly reduces the service life and seriously restricts the application of the self-priming pump.In addition,some large-sized solid phase particles enter the self-priming pump flow field,which impact the fluid flow inside the pump seriously,resulting in a sharp drop in pump performance.Study on the flow characteristics of solid-liquid two-phase flow in self-priming pump,can predict the influence of solid-liquid two-phase flow condition on the external characteristics and internal flow characteristics of self-priming pump,analyze the erosion characteristics of solid phase particles on the wall surface and the motion characteristics of the particles,and provide the theoretical support for the protection of the high erosion rate of the self-priming pump and the selection of the self-priming pump for the specific working conditions.Therefore,the self-priming pump 65ZW30-20 was used as the object,and numerical calculation method was used to study the influence of various parameters of solid phase particles in the transport medium on the erosion characteristics and pump performance of the overcurrent components.The research results showed that:?1?The head and efficiency of the self-priming pump were negatively correlated with the particle concentration.When the particle mass concentration was 90 kg·m^-3,the head decreased by 6.8%and the efficiency decreased by 3.15%,which seriously affected the performance of the self-priming pump.At the same time,due to the impact of particles,the blade head and its adjacent area as well as the suction surface of the blade showed a relatively high erosion rate.Besides,the suction surface of the blade showed random pitting erosion.The erosion rate of the orifice ring area and volute wall were also high,and the erosion of volute wall was particularly serious,which may become the first failure of the flow components like the blades.Through the analysis of particle trajectory,it was found that the lag effect of solid particles compared to liquid phase fluid was an important reason for the higher erosion rate in blade,volute and other areas.?2?It was found that when large impurity particles moved in the impeller channel,the low pressure zone on the side of the particle in the impeller channel would greatly expand.At the same time,the narrowing of the channel on the side of the particle increased the flow velocity in the channel corresponding to the volute area and the channel of blade on the other side,so the high-speed and low-pressure areas appeared in the tongue and volute area.The reverse flow and flow separation around the particle made the particle surrounded by a low-pressure film.This also reduced the skin friction coefficient of impurity particles.The strain rate of impurity particles reached the maximum in the head area of impeller blade and the connecting area of impeller volute,which were also the most likely places for deformation or failure of impurity particles.?3?The influence of large and small size solid particles on pump performance was calculated and analyzed.Based on the average reduction of pump head caused by particles and the average existence time of particles,a method for calculating the average loss of pump output power caused by particles was proposed,which could quantitatively describe the decline of the pump performance caused by large particles.Through the study of the characteristics of the solid-liquid two-phase flow of the self-priming pump,the erosion characteristics of the particles in the medium through the flow-through parts of the self-priming pump were clarified,and the mechanism of the high erosion damage of the impeller and the volute was revealed.The motion characteristics of large-sized impurity particles in the impeller flow channel were calculated and analyzed.The interaction between the flow field and the particles was analyzed,and the mechanism of the performance degradation of the self-priming pump was revealed.The influence of large and small size particles on the performance of self-priming pump was calculated,and the calculation method for calculating the performance decline of self-priming pump was put forward.The solid-liquid two-phase flow performance evaluation system of self-priming pump was improved.