| Looking at the domestic and foreign literature,we can see that the planting pattern of rice depends on the population,topography,and technology level of a country.The United States has flat terrain,and moderate climate which adopts aircraft broadcasting and drill seeding.Japan main adopts transplant planting of higher yield because of a small amount of arable land.China’s farmlands vary in size and distribution,and a variety of rice cultivation methods co-exist.Due to the characteristics of direct rice growth,such as cost savings,synergy,water saving,and easy realization of mechanization,its planting area has gradually increased in recent years.In recent years,the focus of the research on the rice direct broadcaster has been on the water direct sowing,such as rice bud seed sowing machine 2BD series developed by Luo Xiwen.They are all directed to buds that are used in the direct broadcast of water.Most of the traditional rice direct broadcasters in our country use the external groove wheel seeding apparatus or the external groove wheel seeding apparatus to carry out a simple upgrade,which can no longer meet the operational requirements.This paper aims to design a seeding apparatus which has good quality of cavitation,synchronization of seeding points and seedlings,good seeding,high quality podcasting and less failure rate.the main research content and conclusions are as follows:1.Studying on Physical Characteristics of Rice Grains.Dongnong 426 rice belonging to japonica rice is selected as research object because of good market prospect in Heilongjiang Province,and their physical parameters are used as the basic parameters for the subsequent simulation and design of the key components of the metering device.The basic physical parameters of Dongnong 426 rice grain are measured including density,triaxial size,1000-grain weight,moisture content and natural angle of repose.The triaxial size directly determines the size of the subsequent simulated particle filling model,the natural angle of repose influence the structure of the seed box and the form of seeds feeding seed metering device significantly.2.Design and theoretical analysis of seed metering device.The metering device designed in this paper is a combination of spoon type seeding and piston plunging seed metering,meanwhile,this paper completes the overall machine scheme design of the seeding apparatus,expounds the structure coordination relationship and working principle of the seeding apparatus and establishes the mathematical model of the transmission structure.The key components of the spoon taking and rowing seeds is analyzed in depth,and the structural parameters that determine their performance included the diameter of the spoon head,the depth of the spoon head,the inclination angle of the spoon head,and the inclination angle of the spoon neck.The diameter of the spoon head was taken as 1.1 times of the maximum length of the seed grain.In order to ensure that at least four rice are accommodated,the thickness of the spoon head is about three times the average thickness of the rice seeds.The movement of the caving cone is upward and forward compound movement.From the trajectory of the caving cone,it can be seen that the short dwelling process of the caving cone at the bottom is beneficial to improve the quality of the sowing.3.The virtual orthogonal test of the seeding apparatus is based on the EDEM.Taking the experimental speed,scoop angle,scoop angle,and spoon depth as experimental factors,the seed passing index,replay index,and missed broadcast index are used as the experimental indicators for virtual orthogonal test.The corresponding parameters are set before the virtual test.In the course of the experiment,the causes of missed broadcast and replay are analyzed.From the analysis of the range analysis table and the analysis of variance table,it can be seen that the order of the test factors affecting the rate of qualified seedlings is the depth of spoon taking seeds,inclination angle spoon neck,rotational speed of seeding shaft,inclination angle spoon head and the rotation speed of the seeding shaft interacts with the inclination of the scoop head.The order of the test factors affecting repeating seeding is the same with the seeding qualified rate.There is an interaction between the rotation speed of the seeding axis and the inclination of the scoop head.The order of the test factors affecting the leakage rate is the inclination angle of spoon neck,the depth of spoon taking seeds,the inclination of the scoop head,and the rotation speed of the seeding shaft.There is an interaction between the rotation speed of the seeding shaft and the inclination angle spoon neck.According to the principle of high qualified rate,low repeating seeding ratio and leakage rate,the primary and secondary order of factors affecting seedling quality is the depth of spoon taking seeds,inclination angle spoon neck,rotational speed of seeding shaft,inclination angle spoon head,and the optimal level combination is A2B1C2D3,that is,when the rotation speed of the seeding shaft is 20r·min-1,the depth of spoon taking seeds is 8mm,the inclination of the scoop head is150°,and the inclination angle of spoon neck is 118°,the qualification rate of virtual seeding is90.98%,virtual replay rate is 5.17%and virtual leakcast rate is 3.85%.4.Verification tests for seeding devices.The qualified rate of the indoor bench test conducted under the conditions of the combination of the superior factors obtained by the virtual test is less than 2.72%than the virtual test,which is less than 5%and satisfies the precision seeding requirements.The test results show that when the seed rotation speed is 20r·min-1,the seed spoon d epth is 8mm,the scoop angle is 150°and the scoop angle is 118°,the seed metering perf ormance is better.Meanwhile,the discrete element simulation test is feasible for optimizin g the seedling performance parameters. |
