Abstract:In the process of discrete element numerical calculation, such as post spraying, cooling, transportation, storage, feeding and so on, the establishment of particle model is an important factor to affect the accuracy of simulation. The discrete element parameters were calibrated by measuring the angle of repose. The apparatus and method used for determining the angle of repose existed a few problems, such as more sample consumption and cumbersome measurement. Therefore, calibration work for particle parameters was essential. A new apparatus and method were proposed for actively simulation and determination by the cross-sectional profile of particles’ accumulation. The discrete element model similar to pellet feed was established based on the template plate in the software EDEM and Pro/E. The sliding friction coefficient X1, restitution coefficient X2, and rolling friction coefficient X3 were selected as the influencing factors, and the accumulation angle of repose was selected as evaluating indicators, thus the performance optimization experiments were carried out under the quadratic orthogonal rotation design. Based on the software regression analysis of Design-Expert 8.0.6 and response surface analysis method, the relationship between the three influencing factors and evaluating indicator was established. The measured value of repose angle for pellet feed was selected as the chosen target;by using response surface method, the optimal aggregative index could be obtained under the condition that the sliding friction coefficient among pellet feed was 0.41, restitution coefficient was 0.53, and rolling friction coefficient was 0.08. In the end, the discrete element method combined with the apparatus based on injected section method were verified in the test trail. Under the same condition with simulation, the predicted value for angle of repose was 29.43°±0.70°. Under this scheme, field test result showed that the angle of repose for pellet feed was 28.55°±0.37°. In comparison with simulation value, the error of the angle of repose was 3.1%, which showed that the modeling method of pellet feed and the apparatus based on injected section used for determining the angle of repose were validated and available. The research showed that the optimal parameter combination could be used as reference value when selecting the simulation parameters of pellet feed in the DEM simulation. Meanwhile, the parameters calibration method based on the injected section method was feasible, which could provide references for the numerical determination of other agricultural particulate materials.
