| Rice is the main food crop in my country,and rice production is very important to national food security.Direct seeding of rice has become one of the main rice planting methods because of its advantages of saving water and increasing efficiency,saving time and labor.Mechanical seed-metering device is a widely used seed-metering device for direct seeding of rice,but the existing mechanical seed-metering device has problems such as low seeding accuracy,poor seed filling performance,and serious leakage.Therefore,taking the seeds of three hybrid rice varieties with different sphericity as the research object,according to their material properties and mechanical properties,a scoop hole-wheel precision seed-metering device for rice was designed.Using a combination of theoretical analysis,simulation research,bench test and field test,the scoop hole-wheel precision seed-metering device was studied,which provided a theoretical basis for the structure optimization and performance improvement of the seed-metering device.The main contents and conclusions of the research are:(1)Study on material properties and mechanical properties of rice seedTaking three different sphericity hybrid rice varieties Gangyou 3551,Gangyou 898,and Fengliangyou 3948 rice seeds mainly planted in Anhui Province as the research object,the material properties parameters of rice seed,such as water content,triaxial size,thousand grain weight,density,angle of repose,sliding friction angle,as well as the mechanical properties parameters of compression and growth properties were studied.The material properties parameters and mechanical properties parameters of rice seeds were obtained to provide a theoretical basis for the structure design of the seed-metering device.(2)Structure design of the scoop hole-wheel precision seed-metering device for riceAccording to the agronomic requirements for planting 2-4 grains per hole of hybrid rice,the structure of the seed-metering device was proposed,and the working process of the seed-metering device was analyzed.The structural design of key components such as seeding wheel,scoop,shaped hole,protection guard and auxiliary components such as seeding shell and clearing brush was carried out,and the process of seed filling of rice was analyzed by force.The results showed that reducing the rotation speed of the seeding wheel and increasing the supporting force of the seed on the hole can shorten the filling time of the rice seed into the hole.(3)Performance simulation test of the scoop hole-wheel precision seed-metering device for riceThe EDEM software was used to simulate the seeding process of the seed-metering device,and the medium sphericity Gangyou 898 rice seed was used as the simulation object.The qualified rate,replay rate and missing rate were evaluated as indicators,the single-factor experiments,the comparative experiments and the orthogonal rotation combined experiments with two factors and five levels were carried out on the seed-metering device,and the parameters were optimized.The results showed that the seeding performance of the seed-metering device is the best when the rotation speed of the seeding wheel is 25.94 r/min and the hole inclination of the seeding wheel is 34.75°,and the seeding qualified rate,replay rate and missing rate are 87.55%,9.79%,and 2.66%respectively.Using ABAQUS software to simulate the optimized seed-metering device,it is concluded that the maximum contact stress between rice seed and seed-metering device is 0.4934 N/mm~2,which is less than the rice seed stress 1.3115 N/mm~2,and the rice seed will not be damaged under normal seeding conditions.(4)Bench tests and field tests of the scoop hole-wheel precision seed-metering device for riceAccording to the optimization results of the simulation parameters of the orthogonal rotation combination,the rice seeds of Gangyou 3551,Gangyou 898 and Fengliangyou3948 were used as experimental materials,and the seed-metering device bench tests and field tests were carried out.The results showed that the error between the bench tests results and the simulation parameter optimization results is less than 5%,which verified the reliability of the simulation.The qualified rate,replay rate and missing rate of field seeding of 3 rice varieties met all the requirements for precision sowing of rice. |
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