基于康达效应的玉米小区收获机除杂装置设计与试验

Design and Experiment of Separating Impurities Device for Corn Plot Test Harvester Based on Coanda Effect

为了提高玉米小区收获机二级除杂作业效率和质量,解决传统清选除杂装置体积大、流场稳定性差、流场稳定所需时间长等问题,本文基于气流康达效应设计了一种翼型曲面除杂装置,并结合流场理论分析及计算流体动力学与模拟离散元法(CFD-DEM)耦合仿真试验确定其结构参数。通过对流场中的颗粒进行受力分析得知,曳力加速度主要受颗粒密度与直径的影响。设置单因素试验研究该装置对不同密度、不同直径的颗粒混合物分离效果,拟合并得出颗粒各密度、直径与其轨迹线偏转角的关系方程。通过台架试验验证该装置对玉米脱出混合物中轻质杂质分离功能的可行性,试验结果表明籽粒含杂率低至1.014%,作业性能指标满足设计要求。

A device with a wing-shaped curved surface was designed to separate impurities based on the principle of the Coanda effect.The device improved the operational efficiency and separation quality of the second-stage impurity separation device of a corn breeding plot harvester.Moreover,the device solved some problems of conventional devices for cleaning and separating impurities,such as large size,poor flow field stability,and long time to stabilize the flow field.The structural parameters of the device were determined by the theoretical analysis of the gas flow field and the simulation tests by using computational fluid dynamics and discrete element method.Particles in the flow field experienced complex forces,among which the trailing force was the most effective for separating small particles.The magnitude of particle trailing acceleration was mainly influenced by particle density and diameter.Therefore,two sets of single-factor tests were conducted to investigate the separation effect of the device on particle mixtures with different densities and diameters,respectively.By analyzing the experimental results of the single-factor tests,the relationship equations between the density particles and their streamline deflection angles and the relationship equations between the diameter particles and their streamline deflection angles were obtained.Finally,the bench test results showed that the wing-shaped curved surface impurity separation device had a feasible separation function for the light impurities in the mixture after corn threshing.The bench test data indicated that the impurity content of corn kernels was as low as 1.014%,and the operational performance index of this device met the expected design requirements.