Simulation and optimal design of uniform plate of brown rice based on discrete element method

Abstract: Humidifying evenly is the key to moisture conditioning technology. The uniformity of moisture content depends on the material distribution uniformity. Material uniform plate is the chief work part for increasing the material uniformity, and it has an immediate influence on the follow-up material processing quality and production efficiency. In order to improve the humidifying uniformity in the process of brown rice moisture conditioning, a new type of plate called curved-surface material uniform plate was designed on the basis of existing technology. Combined with the material movement rule on the cone material uniform plate, the parabola was set as the curved generatrix of curved-surface material uniform plate. One of the characteristics of the curved-surface material uniform plate was that it enhanced the uniformity of the material thickness by controlling the floating velocity of the material and offered a favorable condition for uniform humidification of brown rice, and moreover it couldn't damage brown rice. In this study, on the basis of the theoretical analysis, the working process of the curved-surface material uniform plate was simulated with the discrete element method (DEM), and it was found that the structure parameters and operating conditions of curved-surface refining plate were the key factors affecting its wok performance through the analysis based on the orthogonal design. DEM is a numerical method used for modelling the mechanical behavior of granular materials. Using the EDEM software, the influence laws of the rotation rate of material uniform plate, the curved-surface form and the feeding rate on the material thickness uniformity were simulated and analyzed. According to the performance evaluation indices of evenly distributing material, the structure of curved-surface material uniform plate was optimized. By the response surface analysis method, the mathematical model between each factor and coefficient of variation was established. The validation test was used to verify the availability and practicability of curved-surface material uniform plate which was created by three-dimensional (3D) printing technology, and the working process of curved-surface material uniform plate was recorded using high-speed cameras. The simulation results showed that the curved-surface form (parabola coefficient) had highly significant effect on the material distribution (P＜0.01), the feeding rate (caliber of nozzle) greatly affected the distribution of the material (P＜0.05), but the effect of plate rotating rate was insignificant (P＞0.05). To verify the correctness of mathematical model, the simulation tests were made under the optimal combination of parameters, and the experiment results showed that there was no significant difference between predicted and observed values. Considering material requirement, the parabola coefficient was 0.02, the diameter ratio of draft tube to curved-surface material uniform plate was 0.1875, and the plate rotating rate was 183 r/min. Under the conditions, the coefficient of variation of material thickness was 4.42%. The simulation results were basically consistent with the validation test results, and the relative error was 2.62%. The results have proved that it is feasible to use the DEM to analyze the performance of curved-surface material uniform plate, and the plate can be used for uniform distribution of brown rice. At the same time, the results show that the curved-surface material uniform plate improves the charge level distribution, enhances the material distribution uniformity, and contributes to the uniform humidification of brown rice.