Simulation of the mixing component of a horizontal air-assisted centralised wheat metering device

Abstract

A horizontal air-assisted centralised metering device involves the use of conveying airflow for mixing and conveying during the seeding process, making it suitable for high-speed precision seeding. This study identified key structural parameters for the mixing component. Computational fluid dynamics (CFD) simulations were used to analyse the influence of the key structural parameters on airflow distribution and airflow velocity. The results suggested selecting a contraction section conical angle of 40° with maximal conveying airflow velocity and minimal airflow pressure loss. A mixing chamber length of 25 mm prevented the retention and blockage. An expansion section conical angle of 20° achieved higher airflow velocity within the expansion section. CFD-DEM (Discrete Element Modelling) coupled simulation were used to analyse the influence of mixing chamber height, seeding rate, and conveying airflow velocity on seed conveying performance. The results indicated that a mixing chamber height of 16 mm ensured stable seed acceleration, reduced the probability of seed-wall collisions. Seed collisions within the mixing chamber and expansion section increased noticeably along with the rising seeding rates. While airflow velocity in the range of 16–25 m s−1 facilitated timely seed conveyance and reduced seed-wall collisions. Verification experiments for the optimal parameter combination of the mixing component indicated that a conveying airflow velocity of 22 m s−1 resulted in the stability coefficient of variation of total seeding mass not exceeding 1.04 %, the uniformity coefficient of variation of seeding mass in each row not exceeding 3.61 %. This research offers valuable insights for structural improvements in the mixing component of the horizontal air-assisted metering device.