Numerical Simulation And Experimental Study On Flow Field Of Horizontal Media Stirring Mill

As a mechanical equipment for producing ultrafine powder by high efficiency grinding and comminuting,the horizontal medium stirring mill is widely used in the fields of metallurgy,mining,food,medicine and other related fields.In this paper,a certain type of horizontal medium stirring mill is taken as the research object.The single-phase turbulence model and liquid-solid two-phase flow model are studied and analyzed respectively,and the influence of the structure and process parameters on the grinding effect is explored.On this basis,the structure optimization and improvement of the dispersing disc of horizontal medium stirring mill are carried out by using the method of computational fluid dynamics simulation and experiment.The main research contents and conclusions are as follows:(1)The single-phase turbulence numerical simulation was carried out on the flow field of the horizontal medium stirring mill.The internal flow field of the mill was analyzed.The influence of different mill structure and motion parameters on the flow characteristics was discussed.It has been found that the effective grinding zone in the grinding chamber is mainly concentrated on the both sides and the outer region of the dispersion disk and the cavity wall area of the grinding chamber.The relationship between the viscous dissipation ratio,which can represent the local grinding efficiency of the grinding chamber,and the rotational speed is a relation of 2.4876 power.At the same time,it was found that an increase in the rotational speed(especially at n>600 rpm)would reduce the energy transfer and utilization efficiency in grinding chamber.The chamber diameter mainly influences the grinding efficiency by affecting the speed gradient of the annular region between the dispersion plate and the cavity wall surface of the grinding chamber,and the increasing of cavity diameter is not conducive to grinding.The viscosity of the material mainly affects the energy transfer and utilization efficiency,and smaller viscosity value during grinding can help improve the energy efficiency of the grinding process.(2)Numerical simulation of solid-liquid two-phase flow in the horizontal medium stirring mill was conducted.The law of flow field,velocity distribution and distribution of turbulence intensity were researched,and then the effects of different production parameters on the flow field characteristics were studied.Comparing with the results in the single-phase turbulence numerical simulation,it is further confirmed that the effective grinding zone of the horizontal medium stirring mill is the both sides and the outer region of the dispersion disk and the cavity wall area of the grinding chamber,and it is found that the grinding effect of the dispersed disk B is obviously better than that of the dispersed disk A,and the flow of the tank is significantly better than the hole.Combined with the research on the rotational speed in the single-phase t.urbulence model,it is concluded that the grinding effect could be enhanced by increasing the rotational speed within a certain range.As the viscosity of the slurry increases,the efficiency of energy transfer between the materials decreases by 20.53%,and when the viscosity is 0.85 to 1.25 Pa·s,the material accumulates above the grinding chamber and is easily clogged,resulting in a sharp drop in the grinding efficiency,and thus grinding.Then,the material with lower viscosity is used as much as possible in the grinding process.The particle size and filling rate of the medium ball should be used in conjunction with the rotational speed and viscosity.(3)Based on the analysis and study of the flow field of the horizontal medium stirring mill,the optimization and improvement scheme of the disperse disc structure were proposed in view of the shortcoming of the dispersing disk of the mill,and then numerical simulation and experimental research were carried out to verify the analysis.The numerical simulations results showed that the field parameters such as velocity,turbulence intensity,shear rate,and viscous dissipation ratio of the flow field in the grinding chamber of the new model are all better than those of the existing models.At the same time,the product size of the new model is found through experiments.Both D50 and D90 are superior to the original organic ones and the distribution width of the particle diameters is narrower,which proves the feasibility and effectiveness of structural optimization and improvement schemes.It provides a reference for the design and optimization of horizontal medium stirring mill and selection of process parameters.