Optimizing the design of a multi-stage tangential roller threshing unit using CFD modeling and experimental studies

Abstract

Rising global population of the world is resulting higher demand for buckwheat being a high-quality food crop. In this study, the multi-stage shearing drum working mode was proposed to solve the problems of easy entanglement, blockage in threshing process due to inconsistency of ripening period, decrease grain breakage rate and loss rate and increase threshing efficiency. The designed threshing unit incorporates key components: frame, feeding wheel, main and secondary threshing drums, discharge unit, and concave plate. FEA and modal analysis were integrated to assure robust structural performance and stability of the threshing components within set limits, which were validated by indoor testing that confirmed the threshing drum’s working frequency did not cause resonance. Single Factor Method identifies optimal conditions: 600 rpm, 7 mm, 1.2 kg/s for minimal grain breakage; 700 rpm, 9 mm, 1.2 kg/s for lowest grain loss. A three-factor, three-level orthogonal experiment validates these findings. In conclusion, optimal results are achieved with a drum speed of 600 rpm, feeding rate of 1.2 kg/s, and a threshing gap of 9 mm thus, minimizing both grain loss and breakage rates.