Fluent-based Numerical Analysis And Optimization Design Of Internal Flow Field Of Pressure Screen

Pulp screening is a complex process,which is accomplished by the pressure difference between the inside and outside of the screen plate and the mechanical motion of the rotor blades.The flow characteristics and screening effect of pulp are influenced by many factors,among which the shape of bar,inclination angle,chamfer,rotor shape,rotational speed and the distance between rotor blades and screen plate are the main factors.At present,domestic pressure screening equipment is mainly optimized and improved by imitating from foreign advanced equipment and based on production practice,which requires a lot of time and financial resources.Using numerical simulation method to simulate and analyze the internal flow field of pressure screen can improve the efficiency of research and save production costs.The existing simulation analysis mainly validates theories related to pressure screening,and discusses the pulp flow state or movement laws in the screening area.It seldom involves the influence of bar shape,inclination angle and chamfer parameters on the screening effect.In order to obtain more accurate research results and guide pressure screen to optimize its structure and parameters,it is necessary to study the screening process of pulp and the influence of main factors on the screening effect.The main contents of this paper listed as follows:(1)The screening theory of pressure screen and the main factors affecting the screening effect are studied.According to the basic structure of the outflow pressure screen and the working principle of the main components,the mechanical structure which has no obvious influence on the flow field analysis is simplified,and the model of the flow field inside the pressure screen is established.(2)By analyzing the flow characteristics of pulp,the pulp is regarded as single-phase fluid.By comparing different turbulence models,RNG k-e model is selected and the mathematical model of pulp flow is established according to the flow equation.According to the characteristics of the model,the finite volume method is used to discretize the model and SIMPLE algorithm is used to solve the flow field.(3)ICEM was used to mesh the two-dimensional geometric model of the flow field inside the pressure screen,and Fluent was used to analyze the numerical value of the lattice model.The effects of two different types of bars on the pressure,velocity and turbulent flow field inside the pressure screen were compared,and the optimum parameters of bar structure,inclination angle and chamfer,were determined.Through the trial calculation and analysis of bar section angle and chamfer,the optimum design parameters are determined.When the bar inclination angle is 22.5°,the chamfer A is 0.15 mm,and the chamfer B is 0.1 mm,the pressure screen has higher screening efficiency.