| Rapeseed and sesame are important high-quality oil crops,and Pakchoi is an important daily vegetable in China.Three kinds of small particle size seeds have similar triaxial sizes and seeding operations.The development of small particle size seed-type collectors can improve the utilization rate of machinery and the efficiency of seeding operations.This topic addresses the problems related to the insufficient types of existing multi-purpose seed collectors for small particle size seeds and the poor adaptability of the type hole,in order to achieve multi-purpose low-loss and precision seeding,this paper designs a small particle size seed multi-purpose centralized precision seeding unit with inclined tooth spoon-type hole filling and air-assisted seeding,seed guide device and ditching device.The major research contents include:(1)Based on the research progress and methods of physical and mechanical properties of small particle size seeds at home and abroad,the mechanical and physical properties of three small particle size seeds of rapeseed and sesame were measured and analyzed.(1)The parameters such as sphericity,density,air suspension velocity and collision recovery coefficient of rapeseed,sesame and Pakchoi were measured,and the similarities and differences of the three small particle size seeds were explored.The results showed that the sphericity of rapeseed and Pakchoi was greater than 95°,and the fluidity was good.The sphericity of sesame was 55.32°,and the fluidity was poor.The collision recovery coefficients between the three seeds and the steel hose were between 0.4 and 0.5.The airflow suspension speed of rapeseed was 6.23 m/s,the airflow suspension speed of Pakchoi was 5.14 m/s,and the airflow suspension speed of sesame was 4.77 m/s.(2)The Poisson’s ratio,shear modulus and rolling friction coefficient of sesame were measured and analyzed by texture analyzer,EDEM simulation and MATLAB image processing technology.By analyzing the compression force-displacement curve through axial compression test,the Poisson’s ratio of sesame was 0.481,and the shear modulus was 2.495 MPa.The sesame simulation model was created by multi-sphere bonding.The simulation test of the angle of repose showed that when the rolling friction coefficient between sesame seeds was 0.01 and the rolling friction coefficient between sesame and ABS material was 0.04,the simulated angle of repose was 30.86°,which was closest to the actual angle of repose.(2)Systematic analysis of research progress on seed release technology in the country and abroad.Combined with the existing constructed type of the small particle size seed metering device and the requirements of planting and seeding,a small particle size seed multi-purpose centralized precision seeding unit was designed.(1)A small particle size seed precision metering device with inclined tooth spoon type hole filling and air-assisted seeding was designed,mainly including the structural design and parameter design of the main parts such as the air distribution device,the toothed spoon drum,and the toothed spoon type hole.The analysis determined that the slope angle of the toothed spoon was 28.6°,the quantity of type holes was 24,the length of the upper edge of the type hole was 4.5 mm,the length of the lower edge of the type hole was 4mm,the height of the type hole was 1.92 mm,the spacing of each type hole was 30 mm,and the air flow transmission speed was not less than 7.16 m/s.(2)Through the calculation of the angle between the seed tube and the ground and the actual installation requirements,the material of the seed guide was determined to be steel wire hose.Taking the sowing depth of rape,chard and sesame as the requirement,the double disc type furrow opener with good adaptability and easy adjustment of furrow opening depth was selected as the furrow opening device.(3)The seed mechanics model was developed for the seed filling,seed taking and seed dropping processes,and the main factors influencing the starting filling angle,seed taking range and starting seed dropping angle were analyzed.The main factors affecting the filling effect in the filling process were determined,including the rotation speed of the tooth spoon drum,the slope angle of the right wall of the hole and the friction coefficient between the seed and the hole.In the process of seed-carrying,the initial range of seed-carrying was related to the parameters such as the slope angle of the tooth spoon,the slope angle of the left wall of the hole and the speed of the rotation tooth spoon drum.Increasing the rotation speed of the tooth spoon drum within a certain range can shorten the seed-carrying process and improve the seeding efficiency.The initial casting angle during the casting process was related to the parameters such as the speed of the rotation tooth spoon drum and the slope angle of the left wall of the tooth spoon hole.(4)Single-factor seeding test of roller tooth height and orthogonal test of type hole structure parameters were done by EDEM.The single factor test of the drum tooth height showed that when the height of the tooth spoon was 5 mm,the average speed and average force of the population of rapeseed and sesame were the most obvious.In the quadratic orthogonal regression combination test,the test factors were the height of the hole,the slope angle of the right wall of the hole and the slope angle of the tooth spoon,while the evaluation factors were consistency factor of variation and average seeding rate per row.As can be seen from the simulation results,the factor of variation in concentration and the average seeding rate per row were 1.69%and 3.7 g/min respectively for a hole height of 1.92 mm,a right wall tilt angle of 8.4°and a scoop tilt angle of 28.6°,and the seeding performance was better.(5)The single factor test of seeding performance of rapeseed,Pakchoi and sesame was carried out,and the influence of tooth spoon drum speed and seed layer filling height on seeding performance was obtained.(1)For rapeseed,when the speed of the tooth spoon drum increases,the factor of variation for consistency of seeding volume across rows tends to increase,and the factor of variation for stability of total seed discharge tended to decrease and then increase,with the better speed of the spoon drum ranging from 10 to 20 r/min;when the filling height of the seed layer increased,the factor of variation for consistency of seeding volume across rows tended to decrease and then increase,and the factor of variation for stability of total seed discharge tended to increase,where the better filling height of the seed layer is 5 to 15 mm.(2)For Pakchoi,the factor of variation for consistency of seeding volume across rows and the factor of variation for stability of total seed discharge generally tended to increase with increasing spoon drum speed,with the best spoon drum speed being between 10 and 20 revolutions per minute.As the filling height of the seed layer increased,two coefficients of variation tended to decrease,then increase and then decrease,and the phenomenon of pulling of the seed layer appeared when the filling height was greater than 25 mm,so the best filling heights for the seed layer were 5 mm,10 mm and 20 mm.(3)For sesame,two coefficients of variation had an overall tendency to decrease before increasing when the speed of the spoon drum increased,with the better speed of the spoon drum being 15-25 r/min;When the filling height of the seed layer increased,two coefficients of variation had an overall tendency to increase first and then decrease,with the better filling height of the seed layer ranging from 5 to 15 mm.(6)The orthogonal bench test was performed to get the sequence and optimum combination of seed bed fill height and tine roller speed parameters that influence the seed dispersal efficiency of a seed collector for rapeseed,Pakchoi and sesame.The orthogonal test results were combined with tooth spoon drum speed and seed layer filling height to obtain the optimum combination of factor levels:20 rpm and 5 mm for rapeseed,10 rpm and 5 mm for Pakchoi and 15 rpm and 10 mm for sesame.(7)Taking 2BFQ-6 precision direct seeding machine as the seeding platform,the field seeding experiments were carried out with the better working parameters of rapeseed,Pakchoi and sesame.The results of the rapeseed trial showed the field sowing rate of 5.19 kg/hm~2,the average plant density of 56 plants/m~2,the factor of variation in the number of plants per row of 7.26%and the factor of variation in the uniformity of sowing of less than 6%;The results of Pakchoi trial showed a field sowing rate of 3.39kg/hm~2,the average plant density of 49 plants/m~2,the factor of variation in the number of plants per row of 8.87%and the factor of variation in the uniformity of sowing of less than 6%.The results of the sesame trial showed a field sowing rate of 3.17 kg/hm~2,an average plant density of 36 plants/m~2,the factor of variation in the number of plants per row of 4.26%and the factor of variation in the uniformity of sowing of less than4%,which was in line with the field sowing requirements. |
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