| Rape is one of the world’s major oil crops. China’s planting area and output of rape is the largest in the world. China’s planting area of rape has reached7million hm2in2009. However, the mechanization level of planting rape is not high because of rapeseed’s such characters as small diameter, light weight and fragile seed epidermis. What’s more, traditional rapeseed metering device is mostly one-row type, which make the seeder need many metering devices to achieve more than one row’s seeding, and the seeder must be complicated in structure. The centralized centrifugal precision metering device for rapeseed designed in this paper can achieve more than one-row seeding with just one seed metering device with the help of centrifugal force. Meanwhile, it simplifies the four work process (namely filling seeds process, clearing seeds process, protect seeds process and pushing seeds process) to two process (filling seeds process and outflow seeds process) which will definitely cause less damage to the fragile rapeseed. This design not only improve the working efficiency and simplify the structure, but also provide a new method for high speed and long width seeding.The research contents of this paper are as follows:(1) Main structure design of the centrifugal metering device. The main structure of the centralized centrifugal precision metering device was determined based on systematic analysis of the status and the development of centralized rapeseed metering device of different types at home and abroad.(2) Key component design of the centrifugal metering device. Parameters of some key components such as the inclination degree of the inner cone, diameter of seed holes and the inclination degree of seed holes were determined through the force and kinematic analysis. Besides, the mechanical and physical properties of rapeseed were also taken into consideration.(3) Performance test of the centrifugal metering device. Metering device with different parameters was manufactured for seeding test. The main evaluation index includes the delivery coefficient of variation, the coefficient of variation of each row’s emissions stability, the uniformity of seed spacing and the crushing rate. The proper diameter of seed holes and rotating speed of the inner cone was determined through the single-factor experiments. The orthogonal experiments show the best results. According to the experiment, when the rotating speed is150r/min, the diameter of seeding holes is3.2mm, the inclination degree of seeding holes is15°, the delivery coefficient of variation is2.38%, the seeding uniformity coefficient of variation is18.2%, and the crushing rate is0.32%.(4) Simulation analysis of the centrifugal metering device’s working process and optimization of structure. Simulation analysis was carried out using EDEM software, the relationship between the average velocity, displacement and the time was determined. Base on these, the optimization design was carried out.(5) Design of a combined centrifugal rape planter and experiment in the field. Based on the experiment of centrifugal metering device, a combined centrifugal rape planter was manufactured and seeding test was finished in the field. Results show that the average seed spacing of the centralized centrifugal precision metering device is80.49mm, and it can meet the needs of rape planting. |
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