PARAMETER OPTIMIZATION AND EXPERIMENT OF A SINGLE LONGITUDINAL AXIAL FLOW FULL-CIRCUMFERENCE SEPARATION THRESHING DEVICE FOR RAPESEED HARVESTER

A discrete element model (DEM) of rapeseed threshing and separation was established based on EDEM software. The simulation results were compared with bench test data, showing an absolute error of 0.33% and a relative error of 55% for threshing loss. The relative errors for the proportion of threshed material on the sieve surface and the left–right distribution ratio of threshed material on the sieve surface were 1.21% and 2.38%, respectively, verifying the accuracy of the simulation model. Secondly, a three-factor, three-level Box–Behnken experimental design was conducted, with threshing drum speed, guide plate angle, and threshing gap as test factors, and threshing loss, proportion of threshed material on the sieve surface, and left–right distribution ratio of the threshed material as evaluation indicators. The influence of each factor on the evaluation indicators was analyzed, and regression models between the test factors and evaluation indicators were established. Through a multi-objective optimization solution, combined with consideration of the actual operating conditions and processing requirements of the rapeseed combine harvester, the optimal parameter combination was determined as: drum speed of 550 r/min, guide plate angle of 75°, and threshing gap of 8 mm. Finally, a prototype was developed based on the optimized structure and operating parameters, and its rapeseed harvesting performance was tested by a third-party inspection agency. Field tests showed a total harvest loss rate of 5.6%, impurity rate of 2.3%, breakage rate of 0.4%, and an operational productivity of 0.57 hm²/h. The performance exceeded the requirements of industry standards. This study provides a valuable reference for the performance optimization of threshing devices.