| Mechanized rice hole direct seeding is a light and simple cultivation technology that can improve production efficiency and reduce labor costs by precisely sowing rice seeds into the soil according to the specified number of grains,hole spacing and row spacing.The existing mechanical rice hole direct seeding equipment has the advantages of compact structure and large adjustment range of sowing volume,but the spacing of sowing units is equal to the row spacing,resulting in a large size when operating in multiple rows,and when there is no trenching and mulching device to work together,the rice seeds are basically located on the soil surface after sowing,which is not conducive to rice growth.In order to solve the above problems,this paper designs a pneumaticassisted seed feeding type seed sower,and the seed taking part is improved based on the type-hole wheel type seed sower,which reduces the volume of the seed sower by shortening the spacing of the seed sower wheel and achieves the sowing requirement of forming rows and holes by pneumatic-assisted seed feeding,and the main research contents are as follows:(1)The overall design and working principle of the air-assisted seed disperser are described.The main physical parameters of the seed disperser are measured for the conventional indica rice "Xiuzhan 15",and the design of key components such as seed dispersing wheels and holes,seed box and seed stirring,seed cleaning,seed protection device,and air-seed mixing chamber are completed,in which the spacing of seed dispersing wheels is 10 cm and the row spacing is 20-30 cm.By analyzing the force and motion of rice seeds in the flow field of the pipeline,the relationship between the movement time of rice seeds and the parameters of pipe length,angle and air velocity was obtained.(2)A discrete element model of rice seed multi-sphere was established based on EDEM,and the effects of changing the structure of seed cleaning and seed stirring devices as well as the depth of the type holes on the seed extraction performance of the seed rower were analyzed by simulation,and the average seed extraction numbers of three scoop type holes with depths of 5.5,6.5 and 7.5 mm were obtained when the rotation speed of the seed rowing wheel was 30 rpm.(3)The flow field model of seed discharge pipe was established,and the inlet flow velocity was used as the boundary condition to investigate the flow field distribution in the seed discharge pipe.Using the pipe height and air velocity as variables,CFD-DEM coupling simulation technology was used to analyze the trajectory and velocity variation of seeds in the seed discharge pipe and investigate the effect of each variable on the seed discharge effect.The simulation results showed that increasing the inlet flow rate in a certain range could improve the hole formation rate and reduce the variation coefficient of hole distance.(4)A pneumatic-assisted seed disperser test rig was built to investigate the performance indexes of the seed disperser: the seed extraction performance of the seed disperser was verified with the depth of the type hole and travel speed as variables;a fourfactor,three-level orthogonal test was conducted,and a response surface analysis was performed based on the test results to determine the range of operating parameters to achieve the ideal seeding effect,and the operating parameters were optimized based on the factorial regression equation. |
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