Hydrodynamic Analysis Of Material Flow In Rice Milling Machine

Rice mill,whose process performance is directly related to the whole rice process’ s good or bad,is one of the most important mechanical equipment in the process of rice making.The working process of rice mill is generally: Driven by the screw propeller,brown rice particles will move into the white room to be whitened at the effect of grinding or friction rubbing.Under the action of airflow,the crushed bran powder will be carried away from whitening chamber to the bran discharge system,finally to the outside of the rice mill.The rice without bran powder can be passed into the next process or be collected up.In the process of rice milling,the movement state of brown rice in the whitening chamber can not be accurately described,the flow situation of airflow filed inside the rice mill is not clear,and the force of brown rice is complex and lack of qualitative analysis.In this paper,the vertical sandy roller rice milling machine of MNML30 type will be token as the prototype,who will be established by the 3D graphics software solidworks.The numerical simulation of brown rice in the whitening will be carried out by the particle simulation software EDEM,as well as the airflow field carried by the fluid dynamics analysis software FLUENT,so as to the interaction of the flow and the particles by the FLUENT-EDEM coupling technology.The main work and conclusions,in this article,are as follows:(1)Based on the discrete element method,the situation of the single particle and stream particles can be simulated and the simulation results can be analyzed by importing the 3D model of whitening chamber,which will establish the dispersed particles’ real model in EDEM.As the rice milling’s results suggest the effective stay time of the brown rice is longer in the case of stream particles state,and the collision numbers is much more than the situation of the single particle.Simultaneously,the curves of the particle’s velocity,the average of total force and the kinetic energy-which are changing with the time-will be cut out by the post-processing module in EDEM.(2)In the article,the finite element analysis software workbench is used to divide the grid of the imported rice mill model,as well as judge the quality of the grid.This mesh file will import to the FLUENT to simulate the airflow field inside the rice mill,with the establish of Slip Grid technique and the set of the base parameters.To analyze the influence of the airflow filed inside the rice mill at different roller speed,three different roller speed is delimited,which are the speed 500 rpm 、the speed of 900 rpm and the speed of 1200 rpm.Compared with the influence of the speed of 500 rpm and 1200 rpm,900 rpm is the best situation to get a stable airflow filed.(3)To analyze the interaction of the airflow and the particles inside the rice mill,the coupling model in the EDEM and the FLUENT is applied.Ensuring the success of coupling,the Hertz-Mindlin contact model in EDEM is selected,also the Euler-Euler model and Saffman Lift drag force model in FLUENT,and the volume fraction ε? is introduced to correct the Fluid conservation equations,as well as the DiFelice method to correct the Fluid resistance,finally match the EDEM and FLUENT simulation time steps.