| Rapeseed precision planter has the advantages of saving time and labor scarcity and suitable for mechanized harvesting. Mechanized precision technology for rapeseed is one of the most important ways to realize the sustainable development of crop industry.In order to the problems which the traditional centralized metering device has high damage,low precision and complex transmission structure, the main objective of research was to improved displacement consistency and achieve precision metering performance. The combination technique of pneumatic-typed cleaning and groove retaining was targeted in this research. Therefore, the pneumatic-typed precision centralized metering device with an shaped orifice of inverted square-cone was researched. The research results were as follows:(1) The overall design was determined based on the systematic analysis of the existing hole-cylinder seed metering technique and combined with the physical properties of rape seeds and agronomic requirements. The structural parameters of main components of the device were determined by using the theory of kinematics and fluid dynamics.(2) The main components of the metering device were designed and results were analyzed. As rapeseed has a spherical shape and it is easy for them to roll, and the inverted tetragonal cone hole was an innovative suggestion that improved precision filling seed and solve hole blocking. The fabrication of groove retaining was an innovative proposal to carry out in this research. A mechanical model of seed holding capacity in the initial state was established. The relationship between the start retaining angle and metering cylinder speed was determined and the value of theoretical retaining angle was obtained. Results proved that the depth of groove has a significant impact on improving metering performance and reducing seed damage.(3) The theoretical research on the seeding process of pneumatic-typed centralized metering device was established. Dynamic and kinematic model of seed filling, cleaning out, retaining and seed dropping were established. The main research factors to affect the performance of seeding processes among previously mentioned parameters were analyzed and their influence were also obtained. The critical filling height, differential pressure of retaining device, maximum support force under appropriate groove depth and dropping angle were calculated.(4) Based on EDEM simulation,the study on lateral width of filling chamber, filling height, the proportion of lateral width of filling chamber and filling height(h/M), influence of hole type and cone angle on filling performance were investigated. The result showed that lateral width of filling chamber and filling performance had a negative significant correlation while filling height and filling performance had a positive correlation. In order to control the proportion of filling height, lateral width of filling chamber(h/M), choosing the convenient type hole and cone angle were the effective means to achieve quantitative filling seed.(5) In order to improve metering displacement consistency and reduce seed damage rate, the performance test of combination of air cleaning and retaining of device were carried out. Single factor test results showed that the device obtained in good seeding performance when seed clearing differential pressure was 250 Pa, retaining differential pressure was 150 Pa, filling height was 27 mm, and rotating speed was 20~40 r/min. Variation coefficient of total displacement stability was less than 2%, variation coefficient of displacement consistency was less than 3%, and the damage rate was less than 0.3%. By means of L27(313) orthogonal experiment design, the optimization experiment of the effect of filling and cleaning process on the performance of seed metering was carried out. Test results showed that increasing the filling height, decreasing rotational speed and using air cleaning could improve performance of rapeseed pneumatic-type precision metering device. The variation coefficient of seeding uniformity was 10.70%, variation coefficient of displacement consistency was 1.87%, and the damage rate was less than 0.2% When the clearing air nozzle was a rectangular section, filling height was 23 mm, air speed was 9m/s and rotating speed was 30r/min,.(6) In order to enhance the central seeding accuracy, decrease the damage rate and make the device suitable for rapeseed precision, the structural optimization retaining groove device was determined which based on optimization test for main structure parameters. The optimum structure composed was that: protecting angle was 120°, depth of groove was(1.0-0.3) mm, and opening end size was 10 mm.The test of metering device for different varieties of rapeseed was carried out by using Hua You Za62, Shuanghua11 and Deyouza988. Test result showed that three varieties rapeseed’s quality feed index decreased while the cylinder speed increased, multiple index rate and miss index rate decreased while the roller speed increased, there was no significant effect on damage rate when cylinder speed was 20~30 r/min. The average quality feed index of three varieties rapeseed was higher than 80%, multiple index was less than 8%, miss index was less than 14%, and damage rate was less than 0.2%.The field experiment was conducted by using Hua You Za62. The test results showed that the variation of seeding uniformity was 20.54% and the average distance of seeding was 76 mm when cleaning pressure was 200 Pa, and cylinder speed was 23r/min. The laser orthogonal testing method for surface leveling was tested, and the surface leveling for emergence uniformity coefficient of variation has positive effect;using the combination methodof random sampling,local control and repeat test method for output of projected was obtained. Whenthe unit speed was not more than 4.0km/h, the number of plants per unit area decreased with the unit forward speedincrease appropriately.However the per plant has higher yieldand improved yield favorably.Innovate point 1: The combination technique of air cleaning and groove retaining was adopted and the complete metering device was designed, which realized to sow seed with single.Innovation point 2: The shaped orifice of inverted square-cone was designed, which could improve the quantitative filling ability of rapeseed and avoid blocking in orifice. |
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