Compared to rice mechanisticmetering device, rice pneumatic metering device has advantages of low number of sowing seeds, high precision of seed metering and low seed-injuring rate. Because the precision of seed metering is difficult to control and the performance of hill sowing is poor, rice pneumatic metering device is difficult to be widely used in field direct-seeding. The control of the precision of seed metering is the key to design metering device. Analysis of the process of dropping seeds helps improve the precision of seed metering and the performance of hill sowing, providing a basis for the design of metering device. Seeds were taken away from sowing disc under positive pressure for blowing seeds. The dropping trajectories and hill sowing performance of rice seeds were studied in this article. A high-speed photography technology was introduced to investigate how the dropping trajectories of rice seeds varied and what influenced the dropping trajectories, on which the equations of the rice's movement were formed. The theory equations were optimized through the average horizontal displacements of actual dropping trajectories and the optimization equations under the different conditions were obtained. The diameter of hill sowing was also measured. As seeds were taken away from sowing disc under positive pressure, seeds gained an initial velocity, which was calledVz and was vertical to the sowing disc. Because seeds moved along with sowing disc rotating before seeds were blown away, the seeds gained the other initial velocity, which was calledVrand was parallel to the disc. Seeds also gained acceleration of gravity under the gravity. In the above factors, the dropping trajectories were spatial parabolic, which was morecomplicated than the plane parabolic trajectories of rice mechanisticmetering device. In order to investigate and count the dropping trajectories of rice pneumatic metering device, a coordinate system was established. Indic hybrid Peizataifeng was taken as research subject in this article, of which water content and average length, width and thickness were 20.5% and 8.97, 2.34 and 1.90 mm respectively. There were 2 dropping trajectories, the trajectory of frontal dropping seed and the trajectory of profile dropping seed. The dropping trajectories and diameters of hill sowing were analyzed by multi-factor experiment under different rotation rates and positive pressures for blowing seeds. The experimental results showed horizontal displacements of the trajectory of frontal dropping seed increased with the increasing of rotation rate, which were less than 5 mm. The frontal trajectory had good stability under positive pressure of 0.1 kPa, and horizontal displacements were stabilized within the range of 45-65 mm. Under positive pressure of 0.2 kPa, the frontal trajectory was unevenly distributed with bad stability. Trajectory of profile dropping seed was little affected by rotation rate. Horizontal displacements of trajectory of profile dropping seed increased with the increasing of positive pressure for blowing seeds. The profile trajectories were stabilized within the range of 0-15 mm under positive pressure of 0.1 kPa. Under positive pressure of 0.2 kPa, the profile trajectories were unevenly distributed. Diameters of the hill less than 50 mm were deemed as qualified, while diameters more than 50 mm were deemed as substandard. The probability of substandard diameter increased with the increased rotation rate and positive pressure. Performance of hill sowing was best with the rotating speed of 30 r/min and positive pressure of 0.1 kPa, of which qualified rate was 96.9%. The optimum height of dropping seeds was 10 cm. This article analyzed dropping trajectories in theory and got the optimal conditions of performance of hill sowing, providing the basis for optimal conditions of hill sowing and the reference for the design of seeding tubes of rice pneumatic metering device.
国家科技期刊平台
NSTL
万方数据
维普
