| Rapeseed and wheat are important oil and cereals crops in the middle and lower reaches of the Yangtze River in China.And the sowing period of the both crops are adjacent to each other,and mechanized seeding processes are closer.Based on comparing and analyzing both the domestic and foreign special-purpose and dual-use seeding technologies,and especially on the basis of mechanical-type,a slot wheeled centralized metering system without clearing and protection equipment for rapeseed and wheat was designed to meet the seeding requirements of the both crops and improve the utilization of the planter.The structural design and parameter analysis of the key components of the slot wheeled centralized metering device were also carried out.The mechanical model of the seeding process was established,and the main factors affecting the seeding performance of the device were clarified.Through simulation experiments,the effects of hole back angle,filling height and the rotational speed on the performance of rapeseed and wheat seeding were determined.Through the seeding performance test,the optimal combination of displacement stability parameters and the overall seeding performance of the device were obtained.It will provide a reference for the structure design of dual-use and low damage mechanical seed metering device.The main research contents are as follows:(1)A slot wheeled centralized metering system for rapeseed and wheat was carried out.The relationship between the gear ratio and the seeding amount per unit area of the device and the main structure and working principle of the device were determined.Through the friction coefficient test and the delivery tube arrangement theoretical analysis,it was determined that the rapeseed and wheat were superior in the tube material and the inner diameter was PVC steel hose,16 mm and the position of the seed tube was that the distance from the seeding groove to the horizontal direction of the ditching beam was no more than 606 mm.In order to adapt to the soil working conditions in the middle and lower reaches of the Yangtze River,meet the requirements of both rapeseed and wheat,a double disc opener were selected.(2)The key components of the slot wheeled centralized metering device for rapeseed and wheat were designed.Which was included seed box,shell,seed churning device and seeding porte,among them,the slot wheel was the main structure.In order to meet the seeding requirements of rapeseed and wheat and control of mechanical seedingmethods for seed breakage and clogging of the slot problem effectively,combined with the material characteristics and agronomic requirements,an oblique tapered hole structure with back angle and an on the sides of the rapeseed and wheat areas slot weel with two rows of staggered holes for rapeseed and three rows for wheat was designed.The total width of the slot wheel was 55 mm,and the width of the single slot of the rapeseed or wheat was 27.5mm.It was determined that the length,width and height of the rapeseed and wheat hole were 3.3×2.9×2.1mm and 8×5×4mm respectively,the hole back angles were no more than 30° and 15° respectively,and the number of single-turn teeth of the hole wheel was 45 teeth and 30 teeth,respectively.(3)The mechanical model of filling,carrying,throwing and deliverying were constructed.For the analysis of the filling process,it was determined that the minimum filling height was 10 mm lower than the reference height;According to the analysis of the seed carrying process,the seed cleaning and seed protection were simplified and the rationality of the device structure was verified;According to the analysis of the seed throwing process,when the hole back angles were no more than 30° and 15°,the maximum seeding angle of rapeseed and wheat can reach 40.8° and 34.4°.The process of transplanting determined that the angle between rapeseed and wheat tube and water level should be no less than 33°.And the influencing factors of the seeding performance were determined,which was the slot wheel speed,filling height and hole back angle.(4)The simulation experiment of the slot wheeled centralized metering device for rapeseed and wheat was carried out.The results of hole back angle test,filling height test and the slot wheel speed test showed that: the rapeseed seeding angle was higher than the wheat,and when the hole back angle of rapeseed and wheat were 20° and 5° respectively,the seeding performance was better;the rapeseed filling performance was relatively stable when the filling height was the base height,the filling height of wheat had little effect on the filling performance;The filling angle of rapeseed wheat gradually decreased and the seeding angle gradually increased with the increasing of the rotating speed,and the slot wheel speed was range from 5r/min to 35r/min.(5)The bench experiments of the slot wheeled centralized metering system for rapeseed and wheat were carried out.The results showed that: The optimal combination of parameters for reducing the coefficient of variation of rapeseed and wheat stability was the hole back angle was 20°,the filling height was the reference height,the speed was20r/min,and the hole back angle was 5°,the filling height was 20 mm,the rotation speed was 15 r/min;When the rotation speed was 10～30r/min,the variation coefficient of uniformity of rapeseed and wheat was lower than 6.00% and 7.00% respectively,thecoefficient of variation of total displacement stability was lower than 1.30% and 1.00% respectively,the breakage rate was lower than 0.5%,and the stirrer sheet centered distribution shaft structure can meet the wheat sowing requirements and can effectively improved the filling performance.Field trials showed that the slot wheeled centralized metering system for rapeseed and wheat can meet the requirements of rapeseed and wheat. |
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