基于DEM的稻谷热泵干燥机叶轮排粮过程研究

Grain Discharge Process of Rotary Valve in a Heat Pump Dryer for Paddy Rice based on DEM

循环式稻谷热泵干燥机采用特殊设计的六叶轮式机构排粮,为了解清楚其排粮过程,调控稻谷循环周期以及改进排粮机构,本文采用DEM对六叶轮机构的排粮过程进行研究。采用LK光流法处理观察视频,获得稻谷流动速度,验证模型。对比结果表明,模型对稻谷流动速度的计算符合事实。模拟结果表明,现有叶轮机构出口处存在稻谷回流问题,降低了排粮效率,也有可能造成机构损坏。将叶轮机构下壳体出口上折段长度缩短为原来的1/2后,避免了实际工作转速下的稻谷回流问题,不漏粮,而且相同转速下排粮流量得到明显提升。受稻谷下降速度限制,随着叶轮转速提高,叶片间的稻谷填充率逐渐下降,造成排粮流量随叶轮转速先提高后下降的非线性关系。改进后的结构最大排粮流量对应的叶轮转速更低。在保证稻谷破碎率和叶轮寿命的前提下,可适当提高转速,减少叶轮排粮机构的数量,降低成本。

The circulating heat pump dryer for paddy rice adopts a specially designed rotary valve with six blades for grain discharge.In order to understand its grain discharge process,regulate the circulating period and improve the structure,this paper uses DEM to study the grain discharge process of the rotary valve.LK optical flow method is used to process the observation video to obtain the grain flow velocity and verify the model.The simulation results show that there is grain recirculation at the outlet of the rotary,which reduces the grain discharge efficiency and may also cause the structure damage.After shortening the length of the upper folding section of the lower shell at the outlet to 1/2 of the original,the problem of grain recirculation under the actual rotational speed is avoided,there is no grain leakage,and the grain discharge flow is significantly increased at the same speed.Limited by the falling speed of grain,with the increase of rotational speed,the filling coefficient between blades gradually decreases,resulting in the nonlinear relationship that the grain discharge flow first increases and then decreases with the rotational speed.The rotational speed corresponding to the maximum discharge flow of the improved structure is lower.On the premise of ensuring the grain crushing rate and the service life of the valve,the rotating speed can be appropriately increased to reduce the number of rotary valves and the cost.