| The rapeseed planting area is large and the production efficiency is low in China.It is important for rapeseed industry to improve mechanized planting level,reduce production costs,and carry out high-efficiency centralized metering technology research.Based on the research on centralized metering technology and equipment at home and abroad,in order to solve the problem that the change of seed-filling mass of centralized centrifugal precision metering device for rapeseed leads to the change of sowing norm in the field,a kind of seed-filling duct like a hourglass was designed,and a kind of way of controlling seed flow by adjusting the volume of the inner cone was put forward.Based on the working principle of centralized centrifugal precision metering system for rapeseed,the mechanical model of filling seed,carrying seed,and throwing seed in three links was constructed,and the working process were divided into three stages.The structure and related parameters of the main device of centralized centrifugal precision metering system were determined.The simulation test by discrete element method software EDEM determined the optimal inside diameter of the flow control section of seed-filling duct,and the seed filling performance of the seed-filling duct was verified to be good by bench experiments.The bench test was developed to research the influence of inner cone's effective volume on the stability of full seeding quantity and the apiece row consistency variation coefficient of seeding quantity.The optimum parameters of centralized centrifugal precision metering system were gotten by bench test,and were verified by field test.The main research contents were as follows:(1)A centralized centrifugal precision metering system for rapeseed with adjustable number of seeding rows and in one device planting multiple rows was designed.This paper elaborated the working principle of the centralized centrifugal,and analyzed the structural principle of the Adjustable number of seeding rows.The mechanical model of filling seed,carrying seed,and throwing seed in three links was constructed,and the dynamic analysis of each link was carried out.The analysis of filling links provided a theoretical basis for the structural design of filling tubes.Through the analysis of carrying seed links,two states of active carrying seed and passive carrying seed were determined.Based on the analysis of throwing seed link,the critical speed of inner cone cylinder was determined to be 78r/min.Based on the movement law of rapeseed seed population in the whole seeding process,three stages of the working process were divided.The three stage were namely towards stable stage,stable stage and ending stage.The bench test and simulation test confirmed that the main factors affecting the stability of total displacementof centralized precision metering were filling seed mass and effective volume of inner cone cylinder.The method to improve the stability of the total seeding of the centralized precision metering was put forward by shortening the stabilizing stage and the ending stage.(2)According to the material characteristics of rapeseed seeds and the agronomic requirements of rapeseed planting,the structure and related parameters of the main device of centralized centrifugal precision metering system were determined.The main structural parameters of the seed box were determined.When the volume of the box was 19.4L,the seed could be filled and sown continuously for 2 ha.The hourglass type filling seed tube was designed,and the basic structure of the filling seed tube was defined.The analysis of the filling process showed that the main factor affecting the filling performance was the flow control section of the filling tube diameter.The discrete element simulation analysis confirmed that when the flow control section of filling seed tube diameter was 8 mm,the filling seed performance was better.The bench test verified its filling seed performance.The method of changing the effective volume of inner cone cylinder by changing the filling volume of convex platform was put forward.Eight convex platforms with different filling volume were designed.Under the filling action of eight different convexes,the effective volume of the inner cone cylinder was 0.657 L,0.581 L,0.505 L,0.429 L,0.353 L,0.277 L and 0.201 L,respectively.According to the requirement of adjustable seeding quantity of rapeseed mechanized planting,the mechanical drive and electric drive were designed.Both driving modes could meet the transmission requirements of centralized centrifugal rapeseed precision metering device,and could realize adjustable speed of inner cone cylinder in metering device,which could meet the requirements of planting in different regions and different planting dates.(3)The test scheme of centrifugal metering device for rape was designed.The main evaluation indexes of the performance test of metering device were determined as stability coefficient of total seeding and variation consistency coefficient of each row seeding.The single factor performance test of centrifugal metering device was carried out with the effective volume of inner cone cylinder as the test factor.The relationship between the stability coefficient of total discharge,the variation consistency coefficient of each row,and the effective volume of inner cone cylinder was determined.Taking the effective volume and rotational speed of inner cone cylinder as experimental factors,the two-factor experiment of centrifugal precision metering device for l rapeseed was carried out.The analysis of variance of two factors showed that the effective volume of inner cone cylinder had significant influence on the stability variation coefficient of totalseeding and the consistency variation coefficient of row seeding.The rotational speed of inner cone cylinder had no significant effect on the stability coefficient of total seeding,but had no significant effect on the stability coefficient of row seeding.The coefficient of difference had a significant effect.When the effective volume of the inner cone cylinder was 0.429 L and the rotational speed was 140r/min,the stability coefficient of the total seeding of the metering device was 5.53%,and the consistency variation coefficient of the row seeding was 4.63%.The centralized centrifugal precision metering system for rapeseed had better metering performance.The minimum critical speed of the inner cone cylinder was 90r/min.With the increase of the inner cone cylinder speed,the total seeding of the metering device increased gradually.When the speed was greater than 160r/min,the total seeding of the centralized centrifugal metering device tended to be stable.The total displacement of the centrifugal metering device could be adjusted within 25-69g/min,which could meet the requirements of different planting rates in the field.(4)Based on the driving mode of centralized centrifugal precision metering system for rapeseed,two kinds of centrifugal seeders were designed according to different working conditions in the field.They were mechanically driven centrifugal planter with no-tillage and trench opening,and electric driven crawler self-propelled centrifugal planter.The post-ditch no-tillage centrifugal seeder is suitable for the middle and lower reaches of the Yangtze River.The average plant spacing of rapeseed was 48.04 mm,the variation coefficient of plant spacing uniformity was 20.75%,and the variation coefficient of plant distribution was 21.35%,which met the agricultural requirements of rapeseed cultivation.Crawler self-propelled centrifugal planter is suitable for soft beach soil,mainly for forage rapeseed seeding. |
PDF Full Text Request