Effect of air pressure on the performance of a centralized pneumatic metering system for rice direct seeding

摘要

Rice is one of the most important food crops in China. Rice direct seeding is becoming more and more popular in China for its low-input demand. The paper involves a centralized pneumatic metering system for rice direct seeding, which distributes seedsto 33 rows through only one metering system. Air pressure in the ejector, which blows rice seeds discharged from the centralized metering device into the distributor, is one of the most important factors for the performance of the metering system. Experiments were carried out through a metering device test-bed PS-12. Air pressure in the ejector was measured to reveal the effect of pressure on the performance and confirm the appropriate pressure range. The results showed that, the coefficient of variation (CV) of seeding quantity between rows reduced with the rise of the air pressure when the air pressure kept in 1.5-3.5 kPa, and increased with the rise of the air pressure when the air pressure higher than 3.5 kPa. Either too high or too low air pressure will affect the sowing quality. Seeds and airflow were mixed unequally under low airflow, while seeds crash delivery pipe and distributor hardly under powerful airflow that lead to bad seeding uniformity and serious damage of seeds. Analysis showed that the metering device has steady performance with the air pressure within the range of 2.5-3.5 kPa.