Numerical Simulation Of Solid-liquid Two-phase Flow Characteristics Of Alkali Liquid Circulating Pump

Alkali circulating pumps are widely used in the important industrial processes such as evaporation and salt production of chlor alkali.It is mainly used to transport solid-liquid twophase media such as ammonia brine,hot alkali liquid,molten alkali and filtrate.The performance and reliability of the alkali circulating pump are demanded by the working environment of crystal solid particle erosion and strong corrosion.With the implementation of the green development concept of chlor alkali industry,it is required that the alkali circulation pump be more energy-saving and efficient.Therefore,this paper will focus on the effect of flow conditions and particle physical parameters on the internal flow of alkali circulation pump and the effect of particle concentration on the mechanical properties of blades.This article was completed under the support of the key project of Jiangsu Key R & D Program "Development and Application of Key Technologies for High-efficiency Chemical Process alkali Circulation Pumps(BE2015001-4)",and a numerical calculation study was carried out on a centrifugal alkali circulation pump.The main work and achievements of this paper are as follows:(1)Based on the numerical calculation,the distribution of pressure,velocity and entropy production in impeller and volute under different flow conditions are studied,and the numerical results are verified by experiments.The results show that the error of head and experiment is 4.69% and the error of efficiency is 1.07%.There is always a low velocity region near the middle of the pressure surface,and the area is negatively related to the flow rate.The energy dissipation caused by turbulence on the blade surface is far greater than that caused by viscosity,and the two kinds of dissipation are concentrated at the blade inlet flange and near the blade outlet;with the increase of flow rate,the area with high energy loss becomes larger,and the distribution trend of diffusion appears on the blade surface.The vortex in the volute channel is broken and converged to form a single vortex by an approximate pair of vortices.The core of the vortex moves to the vicinity of the wall,and the area affected becomes larger.(2)Based on the full factor test and two-phase flow double Euler calculation,the relationship between different physical parameters and pump performance,particle flow law is explored.The results show that the prediction accuracy of the regression equation between the parameters and the properties of particles is 99% in local space.The velocity of the solid phase in the inlet and the middle and back of the suction surface of the blade tends to drop sharply.The effect of particle diameter and particle density on the flow field is similar.With the increase of particle concentration,the wake band of particles at the impeller outlet becomes wider and the solid-liquid two-phase separation is obvious.The change of flow rate has little effect on the position of particle accumulation and has great effect on the degree of particle accumulation.(3)The effects of flow condition,particle mass(diameter,density)and particle concentration on pressure fluctuation and radial force evolution of impeller and volute were studied.The results show that with the increase of flow rate,the peak value and the main frequency amplitude decrease first and then increase;The flow rate of the minimum fluctuation peak in two-phase flow is larger than that in single-phase flow.The amplitude of the main frequency of the pulsation at the volute is positively related to the concentration,but with the increase of the particle mass,the peak value and the amplitude of the main frequency of the pulsation at the volute first decrease and then increase,and the main frequency is at the blade frequency.The peak value of radial force pulsation of impeller is the smallest at 1.2Q in singlephase flow condition and the smallest at 1.4Q in two-phase flow condition;the increase of particle mass makes the peak value of radial force pulsation of impeller decrease first and then increase,while the increase of concentration makes the peak value of radial force pulsation increase continuously.(4)Based on the two-way fluid-solid coupling,the flow field of single-phase and two-phase coupling of alkali circulation pump was studied,and the effect of particle concentration on stress and deformation of blade was analyzed.The results show that,considering the coupling of rotor structure domain,the difference of wave form and phase of pressure,axial force and lift is small before and after coupling,but the amplitude increases slightly,especially under the condition of two-phase flow.The distribution of equivalent stress and deformation of impeller under different particle concentration is similar to that of singlephase flow.The maximum equivalent stress occurs in the welding area of blade outlet and cover plate,and the minimum is at the hub;With the increase of particle concentration,the maximum equivalent stress of impeller decreases and the deformation increases.The deformation of each intersection line at the root of the blade increased from the inlet to the outlet,and was positively related to the particle concentration;The equivalent stress increases sharply near the back cover plate at the inlet and outlet of the blade,and the deformation decreases rapidly;the low frequency signal of the dynamic stress at the root of the blade becomes disordered and the main frequency amplitude becomes larger due to the increase of the particle concentration.