Design And Research On Seeding Device Of Flat Seedling For Small Size Vegetable Seeds

Nowadays in China, more than two-thirds of vegetables cultivation adopted the way of transplanting in production process. However, with characteristics of small size, irregular shape and high impurity content, vegetable seeds created challenges for seeding mechanization. Therefore, most of vegetable seeds were sown in manual or semi-mechanization ways despite the disadvantages of low efficiency, heavy labor intensity, high seed consumption and cost, which increased the cost of vegetable cultivation, limited large scale production of vegetables and influenced the seasonal requirements of vegetables.This thesis focused on sowing mechanization, which was the first process of the vegetable mechanization cultivation. With celery seeds as the object of sowing, a new seeding device for small size seeds was proposed. The contents and conclusions of this paper were listed as follows:(1) Physical parameters of seeds such as size distribution, thousand-kernel weight, density, coefficient of static friction and restitution were measured on two celery varieties, “Liangfeng” and “Huaxianzi”. The results of the measurement provided parameters for the EDEM simulation analysis and basic reference for structure design of the seeding device. According to sowing agronomic requirements, combined with the purity and germination rate of celery seeds, seed quantity of 1500~1700 for every single nursery tray was obtained.(2) A new seeding device for flat seedling was proposed and its working principle was introduced. Based on the transporting device of the rice seeder, the transmission mechanism and main structural parameters of the seeding device was analyzed, and key components were designed.(3) The movement of single seed in the seeding drum and during the seeding process was studied through kinematic analysis. The distribution of the fallen seeds on flat board was simulated and analyzed by discrete element software EDEM. With the sowing density, variation coefficient of horizontal and vertical flow rate as the evaluation indicators, factors which influence the effect of sowing such as conveying speed of the nursery tray, diameter of seeding hole and seed filling rate etc. were analyzed. The results provided fundamental reference for the design and testing of the sowing device prototype.(4) The prototype was designed and assembled. Orthogonal experiment was conducted on factors which influence the effect of sowing, and optimal working parameters were obtained as fellows: conveying speed of the nursery tray was 0.08m/s, diameter of seeding hole was 1.5mm, seed filling rate was 0.1g/s and inclination angle of tile-shaped plate was 0 °. The variation coefficients of horizontal and vertical flow rate were 8.91 % and 8.75% respectively, seeding density was 1.07 grains per square centimeter, and sowing effect of the prototype met the sowing agronomic requirements under the optimal working condition.