Influence of air blower parameters of pneumatic seed-metering system for rapeseed on negative pressure characteristics and air blower selection

The seeding performance of 2BFQ series planter pneumatic precision seed-metering system for rapeseed is affected by load changes, surface features and vibration in field. The pneumatic seed-metering system of 2BFQ series planter for rapeseed is composed of precision seed-metering devices, air blower and air pipelines. The structure and the working parameters of the system such as the number of precision seed-metering device, power rate and rotational speed of the air blower are affected the air pressure inside the seed-metering device and consequently influence the seeding performance directly. When the absolute value of negative pressure is decreased, miss index is increased. When that is increased, multiple indexes are increased. The objective of this research is to choose the appropriate structure and working parameters to ensure the air pressure of seed-metering device in the perfect condition. However, the quantitative analysis and mathematical model of the pneumatic seed-metering system were needed more investigation. The design of the pneumatic seed-metering system depended mainly on experiments the value estimation. To solve the problem, a series of experiments were carried out to study negative pressure effects and pump parameters. First, the negative pressure value of metering device was measured and automatically saved to the PC by pneumatic system testing device. Negative pressure uniformity was analyzed to determine proper point of air cavity which represented the suitable value of the whole negative pressure. Secondly, the effects of rotational speed of metering disc, number of seed-metering device, air blower rated power, air blower operating speed were studied. Thirdly, further analyze were made and mathematical models were established with aid of 1stOpt(First Optimization) to provide a basis for design of the system. Results showed that the negative pressure of cavity was uniform so that any measurement of negative pressure at any point was satisfactory. The rotational speed of metering disc resulted in a negligible impact on the average value of negative pressure. The absolute value of negative pressure increased when the number of metering units decreased or when air blower rated power and rotational speed increased. A mathematical model(M1) was selected to choose an air blower. Then another mathematical model(M2) was developed to estimate the rotational speed which included negative pressure, number of metering units and air blower rated power and rotational speed. Determination coefficients of previously mentioned factors were more than 0.92, verifying relative error within -8.23%-6.62% and -6.12%-8.25% for model M1 and M2, respectively. Mathematical model M1 was employed to describe the number of seed-metering devices and then was used to calculate the air blower power which could be used. Furthermore, mathematical model M2 was used to calculate pump rotational speed by using the negative pressure and number of seed-metering devices. Based on the two models, pump design parameters of metering system were set up as to give the air blower selection and rotational speed to match the 2BFQ series pneumatic planter precision seed-metering system for rapeseed. The system proved to be practicable by investigating it through bench test and field experiments. Research results provided the basics of theoretical methods and guidance for the structural optimization and practical application of the 2BFQ series planter pneumatic precision seed-metering system for rapeseed.