基于离散元的茶叶抖筛机茶叶运动特性分析与试验

为了降低茶叶抖筛机的误筛率，从颗粒动力学角度研究了筛面倾角、振动幅度、振动频率对茶叶颗粒在抖筛机筛网上运动特性的影响。结合离散元方法对茶叶颗粒在筛面的运动进行数值模拟，通过分析茶叶颗粒的筛分过程，明晰了抖筛过程中筛上茶叶颗粒的运移机理。结果表明：茶叶颗粒主要集中在筛网中间，频率太大或者太小都会造成茶叶颗粒在筛网上的横向偏析；茶叶颗粒在筛网上的平均速度、旋转动能与振幅、频率呈正相关，筛面倾角对茶叶颗粒在筛网上的平均速度、旋转动能影响较小，茶叶颗粒沿X轴方向和Z轴方向速度对茶叶颗粒在筛网上的平均速度贡献最大；迁移系数的变化幅度随着筛面倾角、振动幅度、振动频率的增加而呈现逐渐增加的趋势，对茶叶抖筛过程颗粒迁移能力影响由大到小为：振动幅度、振动频率、筛面倾角；当振动幅度为22.5mm、筛面倾角为3°、振动频率为4.166Hz时，茶叶抖筛试验误筛率最小，茶叶抖筛试验误筛率结果与仿真试验结果相差在5个百分点以内，表明DEM模拟具有较高的准确性。

Kinematic Characteristic Analysis and Test of Tea in Tea Vibrating-sifting Machine Based on DEM

In order to reduce the error-sifting rate of the tea vibrating-sifting machine, the effects of inclination angle, vibration amplitude, and vibration frequency on the motion characteristics of tea particles on the sieve were studied from the perspective of particle dynamics. By combining the discrete element method to numerically simulate the movement of tea particles on the sieve surface, and analyzing the vibrating-sifting process of tea particles, the transport mechanism of tea particles on the sieve during the vibrating-sifting process was clarified. The results showed that tea particles were mainly concentrated in the middle of the sieve, and too high or too low frequency could cause horizontal segregation of tea particles on the sieve. The average velocity and rotational kinetic energy of tea particles on the sieve were gradually increased with the increase of amplitude and frequency. The inclination angle had little effect on the average velocity and rotational kinetic energy of tea particles on the sieve. The velocity of tea particles along the X-axis and Z-axis contributes the most to the average velocity of tea particles on the sieve. The variation amplitude of the migration coefficient was gradually increased with the increase of inclination angle, vibration amplitude, and vibration frequency. The order of influence of different parameters on the particle migration ability of tea vibrating-sifting process was as follows: amplitude, frequency, and inclination angle. When the vibration amplitude was 22.5mm, the inclination angle was 3 °, and the vibration frequency was 4.166Hz, the error-sifting rate of the tea vibrating-sifting test was the smallest. The error between error-sifting rate results of the tea vibrating-sifting test and the simulation test results was within 5 percentages, indicating that the DEM simulation had high accuracy. The research result had important reference value for reducing the error-sifting rate of the tea vibrating-sifting machine.