| Pelletizing coating makes it easier to mechanize the production of small grains of forage seed and improves seed sowing efficiency,germination rate,and survival rate.In this study,we designed vertical coating equipment for small grains of forage seeds with a poor coating effect.The optimum working structure parameters of the coating machine were determined by numerical simulation of the mixing effect of seed and powder during the coating process by the discrete element method,and the prototype machine was designed and built,and the best combination of process parameters for coating was sought in the physical test of the prototype machine.The research of this thesis is as follows.1.A pelletizing coating machine is designed to realize pelletizing coating of small forage seeds.The coating machine comprises a supply system(powder feeding device,liquid feeding device),a pelletizing device,and a control system.By analyzing the movement and force of the material in the coating pot,the factors affecting the effect of seed pelleting coating are the coating machine’s rotating speed,the coating machine’s diameter,and the coating machine’s edge angle.2.A combination of physical tests and discrete element numerical simulations was used to calibrate the relevant parameters of red clover seeds and powders.The EDEM software was used to establish the particle model of red clover seeds and powder.The applicable numerical simulation parameters of seeds and powder were calibrated by determining the resting angle of grains and powder particles.The relevant numerical simulation parameters of seed and powder were determined.The coefficients of static and rolling friction of red clover seeds-seeds were 0.605 and 0.637,respectively.The static friction coefficient of red clover seed-steel plate was 0.388,the static friction coefficient and rolling friction coefficient of powder-powder were 0.887 and 0.319,respectively.The surface energy of JKR was 0.162 J/m~2,the collision recovery coefficient of red clover seed-powder was 0.246,the static friction coefficient of red clover seed-powder was 0.776,and the rolling friction coefficient of red clover seed-powder was 0.255.3.The above parameters were used to simulate the seed-powder mixing test numerically.A quadratic regression orthogonal test was conducted with the speed of the coating machine,the diameter of the coating machine throwing disc,the tilting angle of the coating machine edge as the test factors,and the coefficient of variation of the powder as the evaluation index.The test results showed that the optimal working structure parameters were 309.9 mm in diameter,61.9°in the tilt angle of the edge of the coating machine,and 10.1 r/s in the speed of the coating machine.According to the optimal working structure parameters derived from numerical simulation to optimize the design of the pellet granulation coating machine,the optimized and improved pelletization qualification rate increased from 78.6%to 93.1%.4.Optimization tests were conducted on the prototype of the coating machine for the filling rate of the coating pot,the single powder supply,the powder supply interval,and the liquid supply,and the test results showed that when the filling rate of the coating pot was 31.8%,the single powder supply was 5.73 g,the liquid supply was 0.42 m L/s and the powder supply interval was 7.48 s,the seed pellet coating pelletizing rate obtained under this combination of parameters was 98.7%.Through simulation,it was found that the mixing effect of seeds and powder could be enhanced after the introduction of airflow. |
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