Study On Flow Field And Wear In Solid-liquid Two-phase Centrifugal Pump

As the most common instrument in agricultural irrigation,centrifugal pump is widely used because of its simple structure and high transmission efficiency.However,most centrifugal pumps are designed according to the clean water pump,and often face some series of safety problems such as low efficiency and wear when conveying sand water.In addition to the particles in the transport,the factors causing the safety problems of the centrifugal pump are vortex energy dissipation in the flow field.Vortex will produce huge shear force in the energy dissipation,resulting in the internal vibration of the centrifugal pump,causing the fatigue of the blade.In order to improve the efficiency and safety of the centrifugal pump,this study takes the single-stage centrifugal pump as the research object.Through UG modeling,ICEM CFD meshwork and CFD-DEM coupling explored rotational speed（2650r/min,2800r/min,3000r/min）,speed（0.6m/s,1.2m/s,1.7m/s）,viscosity coefficient（0.01 Pa·s,0.1 Pa·s,1Pa·s）,particle volume fraction（2%,3%,4%）and particle size（1mm,2mm,3mm）and particle shapes（spherical,quasi-spherical,triangular）were used to solve the internal flow field and pump wear of the centrifugal pump,and the following conclusions were drawn:（1）The tail of the centrifugal pump blade is a negative pressure area,which is prone to cavitation.The retention area of the outlet pipe is consistent with the area of large vorticity,and the vortex has retention effect.The influence of centrifugal pump speed on the maximum pressure is greater than that of negative pressure.With the increase of flow velocity,the flow field distribution of centrifugal pump outlet pipe becomes more uniform.The increase of rotational speed also increases the overall vorticity of the centrifugal pump,and the influence of rotational speed on the vorticity of each component of the centrifugal pump is successively front and rear cover plates,volute and impeller blades.As the flow rate increases.The large vorticity area at the blade pressure surface increases,the vorticity at the impeller blade increases by 24.56%,the vorticity at the front and back cover plate increases by 10.33%,and the vorticity at volute decreases by 12.84%.（2）The combined control of Q criterion,λ₂ criterion and regularized helicity（H_n）can effectively capture the vortex core region and determine the vortex direction of centrifugal pump.Vortex core in the centrifugal pump mainly exists in the impeller blade,pipe,volute and front and back cover plate connection.By comparing the changes of vortex core inside the centrifugal pump under six working conditions,it is found that the rotational speed has little influence on the distribution of vortex core,vortex direction and vortex energy,while the flow rate has a great influence on the vortex characteristics.With the increase of flow velocity,the downstream vortex decreases and the countercurrent vortex increases,the vortex core in blade clearance increases,and the pipe vortex connects with the vortex at the throat.Solid particles and viscosity coefficient increase can effectively increase turbulent turbulence in outlet pipe of centrifugal pump.（3）The effect of initial flow rate on the residence time of particles is greater than that of rotational speed.The distribution of particles in the outlet pipe of centrifugal pump is gradually uniform with the increase of particle volume fraction and particle size.With the increase of viscosity coefficient,the particles in the flow passage are gradually closer to the blade head,and the particle distribution is no longer single.（4）The tangential accumulated contact energy of the impeller blade in the centrifugal pump is greater than the normal accumulated contact energy.The three most serious wear places of the centrifugal pump are the impeller blade,volute and outlet pipe near the tongue side.In the same speed of centrifugal pump,centrifugal pump wear parts are the same,with the increase of the inlet flow rate of wear increases.It is also found that the influence of inlet velocity on blade wear is greater than that of impeller speed,and the wear of blade pressure surface is greater than that of suction surface.The wear of impeller blade accounted for 38.10%-49.41%of the total wear of centrifugal pump under nine working conditions.When the viscosity coefficient of fluid body increases from 0.001Pa·s to 0.1Pa·s,the maximum wear amount increases,the tongue wear becomes worse,the wear area decreases,and the blade wear shape is spot-like and uneven.When the viscosity coefficient increases to 1pa·s,the maximum wear amount increases.（5）The wear of impeller blade increases with the increase of particle volume fraction,particle size and particle sharpness,and the most serious wear part changes from tail to head with the increase of particle size.The influencing factors of impeller blade wear are particle size,flow rate and speed.The order of particle volume fraction and particle size on the wear of centrifugal pump components is impeller blade,volute,outlet pipe,front and back cover plate,and the influence of particle sharpness on the wear of volute is higher than that of other components.