Numerical Simulation And Experimental Study On The Effect Of High Pressure Micro-jet Parameters On Homogeneity Performance

High pressure homogenization has been widely applied in preparation of micro-emulsions.But in order to improve the homogeneity of high pressure micro-jet,the homogeneous parameters and the microstructure of the homogeneous cavity wall is necessary to further study.The change of homogeneous parameters leads to the change of flow field during the homogenization process,which affects the size and distribution of homogeneous particle size.The micro-structure of the homogeneous cavity wall changes the turbulent flow,so which has some influences on the quality homogeneity.The APV-experimental high pressure homogenizer as the experimental equipment and the oil-water emulsion as homogeneous material,using the method of numerical simulation and experimental study on the combination;the variation law of the flow field and the physical parameters of the flow field effect the homogeneous particle size are analyzed;the effect of micro-structure on the homogeneous performance is discussed by constructing a groove on the conventional homogeneous cavity wall.Based on the working principle of high pressure micro jet homogenizer,the mechanism of oil droplet breakup is analyzed under the impact effect,shear effect and cavitation effect,and the mechanism of oil droplet merger is analyzed.Based on the analysis of the three kinds of homogenization effect and oil droplet merger,the homogenization parameters such as homogenization pressure,initial temperature and oil/water ratio will affect the results of homogenization,which provides a theoretical basis for the experimental study and numerical simulation.A single factor experiment and the orthogonal experiment is carried out to study the homogeneous parameters(homogenization pressure,initial temperature and oil/water ratio)by using High pressure micro-jet homogenizer.Zetasizer Nano ZS is used to measure the particle size distribution of the emulsion and the effects of various parameters on the particle size are obtained.And the optimal parameters are obtained by orthogonal experiments and the main influencing factors are analyzed.Experimental results show that with the increase of homogenization pressure,the homogeneous particle size of oil droplets decreases;with the increase of initial temperature,particle size increases;with the oil/water ratio decreases,homogeneous particle size decreases;and the main influencing factors is initial temperature,homogenization pressure,oil/water ratio in sequence.Homogeneous cavity of homogeneous process in high pressure micro-jet machine is modeled geometry,and the geometric model of homogeneous cavity is meshed.Continuous phase is analyzed by k-?turbulence model,and homogeneous process of discrete phase is simulated by the DPM model.The pressure field,velocity field,turbulent dissipation rate and homogeneous particle size distribution are obtained by simulation.The effects of homogenization pressure,initial temperature and oil/water ratio on velocity and turbulent dissipation rate were studied,and on the regularity of homogeneous particle size distribution was studied.The results show that the drop breakup during high pressure homogenization is affected by fluid velocity and turbulent dissipation rate,and in the region of high flow velocity and high dissipation rate of turbulent flow,the droplets are easily broken;with the increase of homogenization pressure,the homogeneous particle size of oil droplets decreases;with the increase of initial temperature,particle size increases;with the oil/water ratio decreases,homogeneous particle size decreases.The orthogonal analysis of numerical simulation and comparison with the orthogonal experimental results show that the effect of emulsifier on homogeneity at high temperature is obvious.Based on the phenomenon that the change of flow state caused by the wall roughness,constructing a groove micro-structure on the conventional smooth homogeneous cavity wall the smooth homogeneous cavity and the rectangular section groove homogeneous cavity and the triangular section groove homogeneous cavity are numerical simulated respectively,and the results are compared.The results show that the homogeneous cavity with groove which has a smaller particle size than the smooth homogeneous cavity after homogenization,the rectangular section groove homogeneous cavity has a smaller particle size than the triangular section groove homogeneous cavity after homogenization,at the same time the particle size distribution is more uniform.At last,according to the numerical analysis of homogeneous cavity with groove,an optimal design scheme of high shear homogeneous cavity is proposed.