Discrete element method optimisation of threshing components to reduce maize kernel damage at high moisture content

During the mechanised harvesting of maize cobs with high moisture content, kernels will be damaged in different degrees due to their impact with mechanical components, affecting threshing quality. To overcome these problems, a combination of numerical simulation and experimental methods was used to optimise the structure of key threshing components, including the design of a rasp bar threshing element and a variable diameter threshing drum. Based on the discrete element method (DEM), the optimal structural parameters of the optimised threshing components were determined from the force of the maize in the threshing process. To better explore the threshing process, a five-ball bonded maize model was developed to allow the separation of kernels and cobs during the simulation process. Based on this model, the effects of different threshing components on the distribution of threshed kernels were analysed and the simulation results were verified by bench tests. The results showed that compared with the traditional nail tooth and rod tooth threshing elements when the rasp bar threshing elements were used, the proportion of broken kernels was reduced by 31.80% and 46.12% respectively. Compared with the traditional fixed diameter drum, the proportion of broken kernels was reduced by 13.91% when the variable diameter drum was used. It can be seen that the optimised threshing components reduce the kernel damage during the threshing process of high moisture maize and can obtain better working quality.