Simulation analysis and match experiment on negative and positive pressures of pneumatic precision metering device for rapeseed

Positive and negative pressures determine the performance of pneumatic precision metering device for rapeseed. In order to investigate the relationship between positive and negative pressures of nozzles, fluid models of chamber were developed to simulate the airflow, and the k-ε turbulence model was conducted to capture the pressure and velocity of nozzles. Through these efforts linear models were achieved. Meanwhile, the three-factor factorial split-split experiment was designed with negative pressure, positive pressure and the rotating speeds varying from -1 000 to -4 500 Pa, 50 to 250 Pa and 10 to 45 r/min, respectively. The mathematical models were developed through employing the stepwise regression method. The sequence of influential factors on the quality of feed index was positive pressure, negative pressure and rotating speed. To obtain the match regulation of negative and positive pressures with “good” performance, the ratio coefficient K of negative and positive pressures was introduced to build mathematical models. Models relating ratio coefficient K with positive pressure were fitted in different rotating speeds. The results showed that the ratio coefficient was matched Г∈f1(x), f2(x) from the fitting equations with the rotating speed of 10 - 30 r/min; while the rotating speed has greater influence when it was 35 - 40 r/min and the sets Λ∈g1(x), g2(x) were achieved, where x∈100, 250. This study could be conducted to adjust the rotating speed of the pneumatic system to optimize the ideal performance of the seeder.