| Maize is one of the most important food crops in China and its significance in agricultural production is increasing.However,in the context of the expanding scale of agricultural production and the urgent need to liberate the labor force,higher requirements have been placed on the seeding of maize,requires high-quality precision sowing at high operating speeds.With the increase of seeding operation speed,the rotational speed of seeding plate increases,which generates large centrifugal force on the one hand,and on the other hand,the seed filling time decreases significantly,causing serious leakage,which restricts the development of high-speed precision seeding technology.In this paper,we developed a centrifugal variable-diameter pneumatic maize high-speed precision seed-metering device,which the seed group is moved out and the seed quantity is regulated for seed feeding,and achieves efficient and stable single seed filling by combining centrifugal variable-diameter and pneumatic blowing method.The results show that the designed centrifugal variable-diameter pneumatic maize high-speed precision seed-metering device meets the requirements of high speed and quality precision seeding.Details and conclusions are as follows:(1)Combining the triaxial size of maize seeds and the agronomic requirements of seeding,a centrifugal variable-diameter pneumatic maize high-speed precision seedmetering device is designed,the working principle of the seed discharge system is introduced,and the relevant structural parameters of key components are determined through theoretical analysis and design calculations.(2)The discrete element method was used to study the seed movement characteristics of the seed supply device,and the uniformity of seed movement and seed discharge in three types of groove wheels: traditional straight groove wheel,spiral groove wheel and staggered symmetric spiral groove wheel,as well as the force on the seed in the groove,the results showed that the force on the seed in the staggered symmetric spiral groove wheel was smaller,and the seed discharged by this structure was more uniform and continuous.The effect of the inclination angle and length of the staggered symmetrical spiral groove wheel on the uniformity of seed flow was analyzed,and the results showed that the selection of the staggered symmetrical spiral groove wheel with an inclination angle of 45° and a length of 50 mm as the seed supply component of this device can effectively enhance the uniformity of seed flow,reduce the risk of seed damage and improve the seed supply performance.(3)A test stand was built.The single-factor test was carried out by selecting the qualified,multiple,and leakage indexes as the test indexes,and the operating speed,wind pressure and the number of duplicate fillings(NDF)as the test factors,and analyzing the influence law of each factor on the test indexes.The reasons affecting the seed discharge performance were analyzed.The structure of the seed rower was optimized by increasing the inner diameter of the annular cavity and the turning radius of the return pipe outside the shell,and the return pipe outside the shell and the front shell were designed as one piece.After comparing the performance of the seed releaser before and after structural optimization,the wind pressure required by the seed releaser after structural optimization was greatly reduced and the seed releasing performance was improved.(4)The flow field data of the seeding process was calculated by Fluent software,and the multi-body dynamics model was established by Recur Dyn,and the seeding process of the seeder was simulated numerically by importing it into EDEM respectively,and the seeding process of the seed metering device was simulated numerically.The seed inlet velocity was calibrated using high-speed camera technology,and the relationship between seed inlet velocity and wind pressure was obtained as y=1.35x+0.113.The effect of radial mutation length on the seed discharge performance of the seed dispenser was analyzed,and the results showed that the seed discharge performance was relatively good when the radial mutation length of the seed guard was1.5 mm.The effect of seed inlet speed on seed discharge performance was analyzed,and the results showed that when the wind pressure is appropriate,the seed speed is basically the same as the linear speed of the type hole insert,which can ensure a better seeding qualification rate.(5)The quadratic regression orthogonal rotational combination test was carried out to establish the regression equation of each test index.The response surface method was used to clarify the impact of various factors on the experimental indicators.Optimize the experimental results towards the objectives.The experimental results show that the optimal sowing performance is achieved when the operating speed is 14.2 km/h,wind pressure is 1.3 k Pa,and the NDF is 24 grains.At this time,the qualified index is 93.20%,the multiple index is 3.60%,and the leakage index is 1.20%.The seeding system designed in this paper has strong adaptability to the operating speed.The seeding performance of the seeder was tested at acceleration,uniform speed and deceleration,and it was found that the seeding system designed in this paper can complete the continuous operation requirements. |
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