Study On Solid-liquid Two-phase Flow Characteristics In Centrifugal Pump And Correlation Between Particle Impact And Erosion Mechanism

Centrifugal pump is widely used in industrial and agricultural production,but the existence of particles in the transport medium is very easy to cause the erosion of the flow passage parts of the centrifugal pump and lead to the decline of the pump performance.As the core equipment of the process system,once the centrifugal pump fails,it will lead to the stagnation of the whole production process and cause great losses.At present,many scholars have studied the solid-liquid two-phase flow field and particle distribution characteristics in centrifugal pump,but less attention has been paid to the erosion mechanism of particles on the wall of centrifugal pump.In this paper,the relative motion between the particle and the wall is fully considered.Based on the study of solid-liquid two-phase flow characteristics of centrifugal pump,the impact angle and velocity distribution of particles on different flow passage parts and the relevant data of particle impact are obtained.Through the study of particle impact angle and particle impact velocity,the mechanism of erosion and its relationship with the impact motion of particles on the inner surface of centrifugal pump are summarized.The main work and related achievements are as follows:(1)The exterior performances data of HTJ100-80 single-stage centrifugal pump are obtained by standard k-ε turbulence model and compared with the experimental data.The results show that the numerical calculation data are in good agreement with the experimental data,and the head and efficiency errors are less than 3.1%,which indicates that the numerical method is reasonable and reliable.On this basis,the flow characteristics of impeller and volute under different flow rates of clean water are analyzed.It is found that the flow differences between impeller channels under partial flow condition are large,especially in the channel area near the shroud;the flow in volute channel is more turbulent under small flow condition,and the flow instability near the tongue is further intensified.(2)Based on the discrete phase model(DPM),Lagrange method is used to track the particle trajectory in the centrifugal pump,and the solid-liquid two-phase flow characteristics in the centrifugal pump under different particle phase parameters are analyzed.The momentum and energy nonuniformity coefficients are introduced to analyze the influence of particle phase parameters on the flow nonuniformity at impeller inlet and volute outlet.The third generation vortex identification method is used to study the vortex dynamics characteristics at impeller inlet and volute outlet.The research findings indicate that with the increase of particle volume fraction and particle size,the performance curve of the pump decreases in varying degrees,while the blade load and internal energy dissipation increase;the flow nonuniformity at the impeller inlet is higher than that at the volute outlet.The addition of particle phase slightly reduces the flow nonuniformity at the impeller inlet,but greatly increases the flow nonuniformity at the volute outlet.In general,the addition of particulate phase will lead to the deterioration of the flow pattern in the pump.(3)Based on Mclaury erosion model,the wall erosion distribution and erosion data of different flow passage parts at different positions are predicted,and the effects of particle phase parameters and pump operating conditions on the erosion distribution of blade pressure surface and volute wall are compared.In addition,the correlation between particle mass fraction distribution and erosion distribution in the pump are investigated.These findings indicate that the erosion rate of impeller wall is higher than that of volute wall;particle volume fraction and flow condition are the main factors that affect the erosion rate of the flow passage parts,while the particle size and small rotating speed have little influence on the erosion rate.(4)Based on the impact angle and impact velocity of particles,the influence of particle phase parameters and operating conditions on the collision form between particles and wall is analyzed.And the impact angle and impact velocity distribution of blade pressure surface and volute wall as well as the relevant monitoring data on the wall are obtained,so as to identify the different erosion mechanism of the internal wall of the pump.The results show that the high speed impact erosion mechanism with large impact angle of particles is the main erosion mechanism of blade pressure surface,while the low speed cutting friction erosion mechanism with small impact angle of particles is the main erosion mechanism of volute wall;among them,the change of particle size and pump flow rate will have a significant impact on the form of particle wall collision.In addition,through the impact stress analysis of the typical combination of impact angle and impact velocity,the relationship between particle impact and erosion is further elaborated.