联合收获油菜脱出物离散元仿真参数标定与试验

针对油菜联合收获清选装置气固耦合仿真分析中缺乏准确可靠的离散元仿真参数的问题，该研究以宜收获时的联合收获油菜脱出物为对象，基于颗粒离散元法的EDEM仿真软件对主要组分接触参数进行标定。开展了油菜茎秆径向单轴平板全压缩试验，测量分析了油菜茎秆泊松比、弹性模量等特征参数；通过斜面法和自由跌落试验测定了籽粒、茎秆、荚壳和钢板间静摩擦系数及碰撞恢复系数，确定了颗粒模型接触参数取值范围。以茎秆堆积角为试验指标，通过基于EDEM 的Plackett-Burman试验筛选出对茎秆堆积角有显著影响的参数，开展了最陡爬坡试验确定了显著性参数最优取值范围，进一步通过Box-Behnken试验建立了显著性参数与茎秆堆积角的二阶回归模型，优化得出了茎秆接触参数最佳组合。标定结果表明：显著性参数最优组合为茎秆-茎秆静摩擦系数0.707、茎秆-茎秆动摩擦系数0.015和茎秆-钢板动摩擦系数0.012，在接触参数最优组合条件下，茎秆仿真堆积角与实际堆积角相对误差为0.54%。在标定参数组合下，基于DEM-CFD开展了油菜联合收获旋风分离清选装置气固耦合分析，并进行了台架验证试验，仿真试验结果表明：旋风分离清选清洁率为94.42%，损失率为3.96%，与台架试验相对误差分别为2.81%和7.48%，验证了标定参数的可靠性，可为油菜联合收获离散元仿真分析提供基础接触参数。

Calibration and experiment of the discrete element simulation parameters of rape threshing mixture in combine harvester

Existing gas-solid coupling simulation analysis of rape combined harvesting and cleaning device still has the challenge to obtain the accurate and reliable basic parameters that are necessary for discrete element simulation. As a solution, the contact parameters of the components of the rape threshing mixture were calibrated based on EDEM. As the main components of rape threshing mixture, rapeseed, Rape stalk, and rapeseed pod were taken from the rape plant that was ripe and benefitted for the combine harvesting. The radial elastic coefficients and characteristic parameters such as Poisson''s ratio and elastic modulus of rape stalks were measured and analyzed by radial global compression test. Furthermore, the static friction coefficient and collision restitution coefficient among rapeseed, Rape stalk, rapeseed pod, and steel plate were measured by the inclined plane method and free-fall piezocone test, as well as the range of contact parameters of the particle model. By taking the relate error of stalk repose angle between its values of simulation and physical test, Plackett-Burman experiment was conducted to screen out the parameters that had significant influence on stalk repose angle and the optimal ranges of those parameters was further determined by the steepest climbing test based on EDEM. The regression relationship between the repose angle and the parameters that had appreciate impact on the angle was figured out, and the optimal combination of the contact parameters was obtained. The results indicated that the parameters that had significant effects on the stalk repose angle were the static friction coefficient between rape stalks, the rolling friction coefficient between rape stalks, the rolling friction coefficient between steel plate and rape stalk, while the optimal combination of those parameters were 0.707, 0.015, and 0.012, respectively. Under the optimal condition, the relative error of stalk repose angle was 0.54%. To further validating the calibrated parameters, the numerical simulation of cyclone separation cleaning device was carried out based on DEM-CFD method. The bench experiment to compare the performance of the cleaning device with that illustrated by the simulation was conducted based on the test-bench. The results of the simulation showed that the cleaning ratio and loss ratio of the cleaning device was 94.42% and 3.96%, respectively, while the relative error, compared with that obtained in the bench experiment, was 2.81% and 7.48%, respectively. It could validate the reliability of the calibrated parameters. This research could provide the basic discrete element parameters for the simulation analysis for rapeseed combine harvesting.