Design And Experimental Study Of Two-Channel Pneumatic Type Picking Device For Ground Jujube Fruit

Xinjiang is one of the main producing areas of jujube in China,and its annual output of jujube accounts for half of the annual output of jujube in China.Because of its high economic value,jujube has become a pillar characteristic economic crop in Xinjiang.The harvest of jujube in mature period is mainly completed by manual picking,and the problems of insufficient labor force,high labor cost and high labor intensity of jujube picking seriously hinder the healthy development of jujube industry.At present,the domestic development of pneumatic landing jujube picking equipment mainly adopts the single gas path arrangement,and the operation width is small.In the process of picking up,it is necessary to carry or support the pipe manually.After sweeping the strip in a large area,the jujube belt completes the harvesting operation and fails to realize mechanized picking up.Therefore,in view of the small width of the pneumatic landing jujube picking machine and the need for manual assistance to complete the picking operation,this paper develops a two-channel pneumatic landing jujube picking device,which is suitable for Xinjiang dwarfing dense planting jujube garden,increasing the operating range,and realizing mechanized picking.The new landing jujube picking equipment solves the existing problems.The main research contents are as follows:1.Determination of operation parameters of jujube orchard machinery and study on material characteristics of jujube.The planting pattern,row spacing and plant spacing,field land flatness and jujube strip width of jujube orchard in southern Xinjiang were measured.The results showed that the dwarf and close planting jujube orchard was 4m×1.5m(row spacing×plant spacing).The vertical distance between the surface concave and convex and the horizontal datum was 50mm,the width of the strip was 977～1278mm,and the average width of the strip was 1132mm.The physical properties of jujube were measured.The average physical properties of jujube were as follows:the horizontal axis size was 45.23 mm,the vertical axis size was 30.92 mm,the mass was 10.65 g,the water content was 16.74%,and the density was 772.71kg/m~3.The theoretical suspension velocity and suspension wind pressure of jujube were calculated.The suspension velocity range of jujube was 17.77-23.28 m/s.2.Design of two-channel gas path pneumatic landing jujube picking device.The key components of the picking device and pneumatic conveying system,such as picking suction port,follow-up profiling mechanism,suspension lifting mechanism and cleaning box,were designed.The range of structural parameters of the pickup suction port is determined,and the profiling amount and inclination angle of the follow-up profiling mechanism in the two terrain conditions of left high and right low,front high and back low are determined to be 15 mm,6.5°and 7°respectively.At the same time,it is determined that the suspension lifting mechanism meets the bar size conditions of the power lifting range of 250 mm,the model of the electric push rod is selected,and the fan parameters of the gas path system are designed and calculated.3.Numerical simulation of flow field of two-channel gas path picking device.Through the numerical model,it is proved that the two-channel gas path arrangement has no significant effect on the air distribution of the two gas paths of the pneumatic conveying system.It is determined that the pick-up suction port adopts the scheme of installing the middle partition plate;by using single factor test and orthogonal test,taking the velocity non-uniformity coefficient as the index,the optimal parameter combination of the pick-up suction contraction angle,suction width,curling radius and relative height difference structural parameters is obtained:the contraction angle is 100°,the suction width is 50 mm,the curling radius is 7.5 mm,and the relative height difference is 20 mm.The optimal parameter combination model is verified by simulation,which meets the design requirements of the two-channel gas path pickup suction port.4.Device trial production,experimental research and parameter optimization.The processing of the double-airway pneumatic landing jujube picking device was completed.Taking the negative pressure airflow velocity,travel speed,and ground clearance as factors,and the picking rate and mechanical damage rate as indicators,the Box-Behnken three-factor three-level test was designed to optimize the parameters.The optimal working parameters of the double-airway pneumatic landing jujube picking device were obtained through the verification test:negative pressure airflow velocity 32.59 m/s,travel speed 0.34 m/s,ground clearance 40 mm,corresponding picking rate 91.95%,mechanical damage rate 0.26%.