Performance analysis and experiments of seed filling assisted by groove-tooth of pneumatic disc precision metering device for rapeseed

Abstract: High precision of seed metering device is becoming essential to regulate the seeding amount of a direct seeding machine, and to enhance the quality of planting density. A pneumatic seeding technology can be highly expected, due to its low injury rate, good seed adaptability, and large adjustable range of sowing volume. In planting rapeseed, the filling problem can occur during the seeding process with a high velocity using the pneumatic precision metering device, easy to cause serious missed seeding and large working negative pressure. Therefore, an assistant filling plate with groove-tooth directional disturbance was proposed to deal with the filling problem. This study aims to investigate the effects of groove-tooth structure on filling performance in a plate-type pneumatic seed metering device with high velocity and precision for planting rapeseed. An EDEM software, high velocity camera technology and orthogonal test were combined to explore the assisted filling performance, the seed-group mobility under different types and thickness of groove-tooth. This method can be used to alleviate the serious leakage and large demanding for wind pressure power in the seeding process. The EDEM numerical simulation was performed to analyze the influence of different thickness and types of groove-tooth on seed-group mobility during planting. The average kinetic energy and its sum were selected as the quantitative indicators. The results showed that there was a better assistant filling effect in a seed churning device with a linear groove-tooth structure in the thickness from 0.5 mm to 1.5 mm, which helped to improve the seed mobility and inhibit the seed-group drag. In the bench test, the Huayouza 62 was selected, where its 1000-grain weight was 4.4 g, the sphericity was 91.5 %, and the water content was 7.6 %. With the help of high-velocity camera technology, the groove-tooth optimization and assistant filling performance test were carried out to explore the influence of experimental factors on assistant suction performance. According to the model parameters, the smooth plate, arc-shaped and linear seed plate with groove-tooth were produced by the optimized experiment of seed churning device, and thereby they were installed on the top surface of pneumatic precision metering devices during planting rapeseed. It is noted that the seed casing was made of transparent materials for the convenience of observation. Optimized type of groove-tooth was taken as the object, and the thickness of groove-tooth, velocity and negative pressure were taken as experiment factors, while, the leakage absorption rate and the absorption qualification rate were taken as experiment indicators. A three-factor four-level orthogonal experiment was carried out using Design-Expert software. The results showed that when the negative pressure was not less than 1 500 Pa, and the velocity was less than 6.0 km/h, the filling performance for three types of seed plates had little difference. When the velocity was 6.0-9.5 km/h, the assistant filling performance of seed plate with the linear groove-tooth was better than that with the arc groove-tooth and smooth plate. In three factors and four horizontal orthogonal experiments, the optimal was achieved for the filling performance of 1.0 mm thickness, further to clarify the influences of thickness of groove-tooth, negative pressure and velocity on suction performance. The optimal conditions of groove-tooth can be obtained: the thickness of 1.0 mm, the negative pressure of 1 500-2 500 Pa, the velocity of 2.6-9.5 km/h, the adsorption qualification rate was not less than 96 %, and leakage rate was not more than 4 %. The findings can provide a sound reference for the optimal design of pneumatic seed metering device in plate type with high velocity and high precision for planting rapeseed.