| Rapeseed is a kind of important oil crops with the small diameter and easy damage, its disadvantage confines the development of planting in the field, Yangtze River area is the most famous place to cultivate the rapeseed, the level of planting rapeseed is still very low. But with the development of daily life, the domestic demand of plant oil could not meet the requirements, so to develop the mechanical level of planting rapeseed become a urgent task.As we all know that the key part of seeder is the metering device, so the performance of direct seeder for rapeseed is determined by the metering device. This study was based on the pneumatic precision metering device; the experiments were conducted to study the relationship between the operational parameters, EDEM and ANSYS were used to simulate the metering processes, the dropping process of rapeseed in the metering device was applied by the high-speed camera to capture the trajectories of rapeseed during different positive pressures, the simulation and experiments would conduct to investigate the relationship between the parameters of chambers, the outlet of negative pressure chamber, the inlet of positive pressure chamber and the volume of chamber were considered to optimize the structure of chamber.(1) According to negative pressure, positive pressure and rotating speed of metering device, the three-factor factorial split-split experiment was introduced to investigate the relationship between negative pressure and positive pressure, and the rate coefficient of positive and negative pressures was firstly employed to describe the relationship between them, quality of feed index, miss index and multiple index of metering device were conducted to build the mathematical model, the most important factors and the influence between them in the experiments were analyzed, to make sure the stable performance of metering device with quality of feed index above90%, the operational parameters were concluded for the models.it was the first time to introduce the negative and positive pressure coefficient to express the relationship between positive pressure and negative pressure.(2) The processes of pneumatic metering device was divided into three stages including filling process, suction process and dropping process, the simulation software EDEM, ANSYS and high-speed camera were conducted to study the processes, the results were as follows: ①The filling process was simulated on EDEM, when the rotary speed was15rpm, the law of rapeseed flowed from the seed box into the shell was studied to investigate the average velocity of rapeseed during the whole process, the influence factors were analyzed through the simulation, the single rapeseed was chose to capture during the filling process, then the velocity was conducted during the process, the results showed that the velocity of mass dropped as the exponent relationship;②Dynamic model of rapeseed during the sucking process was conducted to analyze the minimum negative pressure, the negative pressure fluid model was built in ANSYS/CFX with the range of negative pressre-1000～-4500Pa, the pressure contour of negative pressure area was captured, and the pressure and velocity of nozzle were calculated through the software, the results showed they would increase with the increase of negative pressure in the outlet;③Analyze the dropping process of rapeseed in the positive pressure area to build the dynamic models, the factors were conducted in the models, the positive pressure fluid model was built in the ANSYS/CFX with the positive pressure of inlet50～250Pa, the pressure and velocity of nozzles in the positive pressure area were calculated, and the high speed system was introduced to observe the dropping process in the experiments with the rotating speed15rpm and25rpm, positive pressure50～600Pa, respectively. The coordinate of rapeseed was found in the video and conducted through special software, the parameters of horizontal distance, velocity and acceleration for rapeseed were calculated to compare with different rotating speeds, and the influence of horizontal distance was investigated with the structure of seed spout, the results showed that when the rotating speed increased from15to25rpm, the horizontal distance and velocity increased.④The high-speed camera system was conducted to observe the filling and suction process, the results were investigated through the picture and video. It was the first time to separate the metering process of pneumatic metering device, the filling process was simulated by the EDEM, and the sucking process was achieved in the ANSYS, the high speed camera technology and target technology was applied to capture the trajectories of rapeseed. The processes of metering device were studied through simulation software; it could express the working principle of pneumatic metering device;(3) The structural parameters of chambers in the metering device were simulated through ANSYS; the pressure contour in the chambers was formed and compared with different parameters of diameters of inlet and outlet, volume of chambers, number of nozzles, the relationship between the parameters and pressures and velocity of nozzle was analyzed, the results showed that inner diameter of outlet in the negatie pressure area had significant influence in pressures and velocity of nozzles;(4) The experiments were studied on the JPS-12performance testing system in the lab, the different parameters were analyzed with diameters of inlet and outlet in chamber from6-12mm, volume of chambers from62-110mm, the position of outlet in the chamber in15,90and125degree, the single factor experiments were studied, in order to investigate the change of performance of metering device, the operational parameters were considered to determined the optimal parameters, it could be applied to optimize the structure of chamber in the metering device. |
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