Objective To solve the problems of slow speed and inefficiency in mechanical seeding of rice.

Method Rice was directly seeded using the air distribution seed-metering device. An α-R air distribution seed-metering device was designed and optimized. It consisted a bell type lumen with adjustable R and a shunt seal cap with adjustable α. Numerical simulations of air distribution and metering process were performed by using EDEM-Fluent coupling module, and the bench test on seeding performance was carried out.

Result The simulation results showed that the highest velocity of rice particles in the combined α-R distributor was 5.416 m·s^-1. The area of vortex stagnation was smaller than that of the traditional structure. Rice particles were discharged smoothly from the dispenser. When R=180 mm and α=20°, the variation coefficient of uniformity was 24.56%, the variation coefficient of consistency among rows was 3.79%, the variation coefficient of total displacement stability was 1.23%, and the three indicators were all the optimum values. Bench test was carried out using distributors printed by 3D printer and the results showed that the variation coefficient of uniformity for the seed-metering device was 29.17%-30.86%, the variation coefficient of consistency among rows was 4.13%-4.33% and the variation coefficient of total displacement stability was 1.4%-1.7%, which met the requirements of mechanical seeding of rice.

Conclusion The results from multiple tests are stable and close to the simulation results. The designed air distribution seed-metering device can meet practical requirements, suggesting that using the EDEM-Fluent coupling simulation is correct and feasible.