Numerical Simulation And Analysis Of Solid-Liquid Two-Phase Flow In Whole Flow Channel Of Canned Motor Pump

With unique and excellent sealing performance,the canned motor pump assumes important roles in engineering fields like nuclear energy,aerospace,chemical,pharmaceutical,and food.In practical applications,solid particles involved in the conveyed medium often cause blockage of the external circulation pipe and wear of the stator and rotor shielding sleeves and bearings in the motor chamber,which directly affects the stability and safety of the pump.The study on the solid-liquid twophase flow characteristics of the canned motor pumps is of great significance for optimization design and operation of the canned motor pump.In the presented thesis,the canned motor pump assisted with external circulation studied,and the inhomogeneous multiphase flow model based on Eulerian-Eulerian method is employed to simulate the solid-liquid two-phase flow in the whole flow channel of the canned motor pump.The commercial computational fluid dynamics(CFD)code ANSYS CFX is used as the solver of the equations governing the fluid flow.Main works and conclusions are as follows:1.The methods for simulating solid-liquid two-phase flows are analyzed.A numerical model is established and verified.Regarding the transport of the solidliquid mixture featured by high solid phase concentration and small particle size,the Eulerian-Eulerian method is selected.The computational domain corresponding to the whole flow channel of the pump is constructed,and is discretized using unstructured grids.A grid-independence examination is performed.A performance test of the canned motor pump is conducted,and the test result is compared with corresponding numerical data.It shows that the relative deviations of pump head and efficiency are5.2% and 4.3%,respectively,which are acceptable for engineering applications.Therefore,the physical validity of the numerical model is proved.2.Effects of the volumetric flow rate,particle size and solid volume fraction(SVF)on performance of inner flow of the canned motor pump are investigated.With increasing flow rate,the pump head decreases,and the pump efficiency increases first and then declines.With increasing particle size,both pump head and efficiency decrease.As SVF exceeds 0.2,the pump efficiency decreases considerably.The pressure in pump chamber and the flow channels of the motor chamber rises with increasing particle size.At a particle diameter of 0.4 mm,high pressure arises at the outlet of the pressure side of the blade.Local pressure and SVF at the rear bearings in the motor chamber are apparently higher than those associated with the front bearings.With increasing SVF,pressure in the pump chamber increases continuously,and the inlet pressure increases first and then decreases.The maximum arises at an SVF of 0.1.When SVF is further increased to 0.25,accumulation of particles is seen at both pressure and suction sides of the blade,raising the possibility of abrasion of the blade.In the clearance of the front and rear thrust disc in the motor chamber,local SVF increases with particle size and then decreases,and reaches its maximum at a particle diameter of 0.2 mm.3.Local SVF at the rotor and stator shielding sleeves is analyzed.A prediction of abrasion of the rotor and stator shielding sleeves and the bearings is implemented at different particle size.With increasing particle diameter,the ability of the particles’ passing though the circulation pipe and the motor chamber is weakened.At a particle diameter of 0.1 mm,the time required for particles to pass through the circulation pipe is shorter than that associated with the motor chamber.With increasing SVF,the ability of the particles’ passing though the circulation pipe attenuates,while the particles pass through the motor chamber with a shortest time.As SVF exceeds 0.25,the time for the particles to pass through the circulation pipe is considerably extended,increasing the risk of blockage of the circulation pipe.The abrasion of the rotor and stator shielding sleeves occurs at the rear bearings with a high possibility.With increasing particle diameter,local SVF at the rear bearings increases,which results in an increased risk of abrasion.Meanwhile,the risk of blockage of the clearance in the motor chamber is increased.