| As is known that the structure and transmission system of traditional planter on which the traditional metering device only for one line is the core part are complex.In this paper,a pneumatic cylinder-type centralized precision metering device for rapeseed was designed.In order to improve the filling performance of the centralized metering device,a knurled cylinder was developed.The main contents of the paper are as follows:(1)The experiments were conducted to test and analysis the mechanical properties of rapeseed.With "Huayouza 62","Zhongshuang 11" and "Zhongyouza 19" as the research object,dimensions,spherical degree and compression mechanical properties of different kinds of rapeseed were tested.The results showed that the long,wide,height and spherical degree are the normal distribution,and the spherical degree of three kinds of rapeseed were above 90%,and the spherical degree of "Zhongshuang 11" rapeseed is the highest.The curve between compression pressure and displacement of different types of rapeseed were basically the same trend,and the effects of rapeseed average diameter on yield load,maximum load and yield displacement were highly significant.(2)The whole structure design of the pneumatic cylinder-type centralized precision metering device and the parameter design of the knurled cylinder were conducted.Based on the analysis of the existing pneumatic roller type metering device,according to the material characteristics and agronomic requirements of rapeseed,the overall design scheme of the centralized metering device was determined.And the paper expounded the whole structure and working principle of the device.The diameter of the cylinder was120 mm,each row radial hole number was 30,knurling modulus was 0.3.(3)The theoretical research and simulation analysis on seeding process of the centralized metering device were conducted to research the influence of different factors on filling process,retaining process and throwing process.In order to study the effects of the knurled structure on seed filling performance,the EDEM simulation was conducted to study the effects of the knurled structure,cylinder rotational speed and seed filling height on seed dynamic characteristics.The results showed that: Increasing the friction between the cylinder and rapeseed can increase the seed filling angle,thus improve the filling performance.The cylinder rotational speed and seeding filling height affected the seed filling angle and towing angle.With the increase of the cylinder rotational speed,the normal force and tangential force between cylinder and rapeseed,and the total force and velocity of the rapeseed linearly increase.With the increase of the seed filling height,thetotal force and velocity of rapeseed linearly increase.The rapeseed dynamics characteristic when the cylinder was knurled was better than the normal cylinder.(4)Bench experiments on the seeding performance of the pneumatic cylinder-type centralized precision metering device were carried out.The single factor test and orthogonal test were carried out with hole diameter,throwing angle,the negative pressure,the positive pressure,the cylinder rotational speed and filling height as the experimental factors.The single factor test results showed that when the hole diameter was 1.2mm and the throwing angle was 60 degree,the performance of the device was the best.When the negative pressure was-2500 Pa,the positive pressure was 500 Pa,the seed filling height was-5mm,and the cylinder rotational speed was 30r/min,the seeding performance was the best,when the quality index was 90.10%,the loss index was 1.56%.When the cylinder rotational speed was between 15 and 50 r/min,the coefficient of variation of each line displacement consistency,the coefficient of variation of the total displacement stability and rapeseed damage rate were less than 5.5%,2.0% and 0.2%.The results of orthogonal test showed that the effects of filling height,cylinder rotational speed,positive pressure and negative pressure on the coefficient of variation of each line displacement consistency were highly significant,while the interactions of each factor were not significant.And the effect of negative pressure on the coefficient of variation of the total displacement stability was significant,while filling height,cylinder rotational speed,positive pressure and the interactions of each factor were not significant.(5)The results of the field experiment showed that the average distance was65.62 mm,and the coefficient of variation of the spacing was 14.99%,which satisfied the technical requirements of rapeseed planter.This paper provides a reference for the structure optimization of centralized precision metering device and improvement of seeding performance. |
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