Numerical Simulation And Experimental Research Of Hydrocyclone For Fracturing Flow-back Fluid

This article focuses on the background of fracturing flow-back fluid desanding,and takes the hydrocyclone as the research object to reveal the separation mechanism,improve the solid-liquid separation efficiency and reduction of energy loss under different gas liquid ratio(GLR).The fluid dynamics software Fluent and experimental methods are used to carry out research on the influence of different gas liquid ratio and degree of gel breaking on hydrocyclone.Flow patterns and equation models(FP-EM)are used to research the optimum range of inlet velocity.Based on the stability of the air core in the internal flow field,the inlet range of inlet velocity was determined to be 4 m/s-14 m/s.Based on the energy loss of the flow field in the hydrocyclone,the optimal range inlet velocity was determined to be 4 m/s-10 m/s.The formation process and morphology of the air core were studied within the optimum range of inlet velocity.The results show that,when there is no air in the material,the external air is sucked into the internal flow field through the negative pressure zones of underflow port and overflow port to form an air core.When there is some air in the material,the air in the air core is mainly from the underflow port and the overflow port and ultimately flows out through the overflow port.Under the condition of charging with constant inlet liquid flow,as the gas-liquid ratio(GLR)increases,the wall pressure,underflow pressure difference and overflow pressure difference all show a trend of non-linear growth,with the increase of GLR,the tangential velocity increases,but the Rankine vortex index declines at lower GLR(10-20%).The axial velocity increases continuously with the increase of GLR,but the excessive GLR(GLR>40%)increases the instability of the flow field.The increase of GLR increases the desanding efficiency of the hydrocyclone and reduces the cut particle size.When GLR is lower than 30%,the Rankine vortex index is small and the separation efficiency is low,and when GLR is higher than 40%,the energy loss is large,so the range of optimal GLR is determined to be 30-40%.Within the optimum range of inlet velocity,under the condition of constant gas-liquid flow,the peak value of tangential velocity increases while the GLR increases,whereas the pressure and pressure drop decrease.With the increase in the GLR,the axial velocity decreases,and the locus of zero vertical velocity shifts inward.The increase in the GLR causes more gas to collect at the vortex finder,which hinders the discharge of the solid-liquid mixture from the overflow,and the larger the GLR,the faster the decrease in the split ratio.The separation efficiency of particles with a particle size of 15 ?m is increased by 6.75%,and the separation efficiency of particles with a particle size of 30 ?m is increased by 0.57%.Meanwhile,the separation efficiency is increased by 2.43%,and the cut size(d50)is reduced as the GLR increases.With decreasing degree of gel breaking,the pressure decreases by 22.35 kpa,the negative pressure area increased from 3.61mm when the viscosity was 1 mpa.s to 4.54 mm when the viscosity was 6 mpa.s.The mean value of tangential velocity decreases by 0.84m/s,Rankine vortex index decreases,which reduces the centrifugal inertia force of solid particles in the internal flow field.The axial velocity increases and the locus of zero vertical velocity(LZVV)moves to wall.External characteristics shows that the total separation efficiency decreases from 72.19%when the viscosity is 1 mpa.s to 32.59%when the viscosity is 6 mpa.s.With the decrease of degree of gel breaking,the separation efficiency and energy loss decreases and the relationship between internal flow field and external characteristics under different degrees of gel breaking was obtained.