Simulation and parameter optimization of high moisture rice drying on combine harvester before threshing

Aiming at the problems of conveying, threshing and cleaning devices blockage while harvesting the high moisture by combine harvester, the idea of reusing waste heat of combine harvester to dry rice on machine before threshing was put forward. The surface moisture of rice dried by hot air in cutting header was studied. The computational fluid dynamics (CFD) coupling discrete element method (DEM) simulation experiment based on the quadratic orthogonal rotating center combination test method was performed. The impact of feeding amount, hot air velocity, hot air temperature and initial water content of rice on the rice dehydrator rate was analyzed and the relationship model between them was built. The optimal solution for the rice drying was obtained using the relationship model. A test bench was set up to validate the accuracy of the model. The results demonstrate that each factor significantly influences the dehydration rate with their important order as follows: rice feeding quantity > rice initial moisture content > hot air temperature > hot air velocity; the optimal solution is rice feed quantity of 100 g, hot air velocity of 6 m/s, hot air temperature of 150 °C, initial moisture content of 20% and a maximum dehydrator rate of 1.541%; the validation test confirms that the acquired relationship model exhibits sufficient prediction accuracy with the maximum relative error of 8.5%.