抛物母线叶片螺旋输送机运移及接触特性分析

Analysis of Transport and Contact Characteristics of Parabolic Generatrix Blade Screw Conveyor

粮食乃生存之本,为了提高水稻种子生产运输的时效性,设计了一种抛物母线型叶片的螺旋输送机。采用离散单元法(discrete element method,DEM)的颗粒系统仿真,探究螺旋输送机输送水稻种子的运动规律,提高水稻种子卸料速率的同时降低叶片损耗。建立Hertz-Mindlin软球干颗粒接触模型,通过对比普通直母线叶片,分析了3种螺杆倾角下不同螺旋转速水稻种子的运移与接触特性。研究结果表明:抛物母线叶片将水稻种子的动能变化表现为加速入料、稳定输送和高速卸料3个工作阶段,且水稻种子在沿螺杆轴向前进的同时还具备不同频率和幅度的周向运动。相同转速下,600 r/min的0°倾角抛物母线叶片稳定输送水稻种子的卸料速率最高为82.3 g/s,但90°倾角的水稻种子回流现象较为明显,平均卸料速率降低了77.8%。相同倾角下,45°的1800 r/min高转速时,抛物母线叶片水稻种子的法向重叠量相较直母线叶片最大减小了10.2%;90°倾角下1300~1800 r/min中高转速时,抛物母线叶片水稻种子的平均接触数小于直母线叶片1.3%,降低了运输过程中叶片的磨损程度。研究结果揭示了水稻种子的运移规律,可为螺旋输送机的机械化高效运输提供理论依据。

Grain is the foundation of survival.In order to improve the timeliness of crop production and transportation,a kind of screw conveyor with parabolic blade was designed.Discrete element method(DEM)particle system simulation was used to explore the motion law of rice seeds transported by screw conveyor.Improve the discharge rate of rice seeds and reduce the blade consumption.A Hertz-Mindlin contact model was established to analyze the transport and contact characteristics of rice seeds under three helical angles and different helical speeds by comparing the ordinary straight generatrix blades.The results show that the parabolic generatrix blades express the kinetic energy change of rice seeds into three working stages:accelerated feeding,stable conveying and high-speed discharging,and the rice seeds also have different frequency and amplitude of circumferential motion while advancing along the axial direction of the screw.At the same speed,the highest discharge rate of 82.3 g/s is achieved for 0°inclined angle parabolic generatrix blades stabilized transport of rice seeds at 600 r/min,but the phenomenon of rice seed reflux is more obvious at 90°inclined angle,and the average discharge rate is reduced by 77.8%.At the same inclination angle,the normal overlap of rice seeds at 45°with a high speed parabolic generatrix blades at 1800 r/min is reduced by a maximum of 10.2%compare to straight generatrix blades.The average contact number of rice seeds in parabolic generatrix blades is 1.3%less than straight generatrix blades at 1300~1800 r/min of 90°inclined angle,which reduces the degree of blade abrasion during transportation.The research reveal the transport law of rice seeds,which can provide a theoretical basis for the mechanized and efficient transportation of screw conveyor.