Distribution characteristics and parameter optimisation of an air-assisted centralised seed-metering device for rapeseed using a CFD-DEM coupled simulation

A numerical study was carried out on the motion characteristics of rapeseeds in the two-phase flow of the distribution head of an air-assisted centralised seed-metering device based on coupled simulations using computational fluid dynamics (CFD) and discrete element method (DEM). The effects of various structural and working parameters on seed motion characteristics and airflow field were investigated. The results showed that motion characteristics, collision frequency and the residence time of seeds significantly varied. Studies of the effect of structural parameters showed that an appropriate diameter to height ratio (e.g., 2.0), lid angle (e.g., 120°) and distribution head with streamlined design could effectively facilitate the movement of seeds, reduce the frequency of seed–seed and seed-wall contacts, avoid excessive residence of seeds, and improve distribution performance. With increasing airflow velocity, the movement and seed-wall collision of seeds became more intense, and the average residence time reduced. Distribution uniformity and power consumption were improved for airspeeds of 20–24 m s−1 with the different rapeseed feed. The coefficient of variation of seed distribution measured in a bench test was less than 5.0%. The results will contribute to improving knowledge of the seed distribution characteristics and optimising the structure of distribution heads for the air-assisted centralised seed-metering devices.