Study On Drying Rice By Far Infrared And Hot Air In Screw Conveyor Of Harvester

In order to solve the problem that rice cannot be dried in time and mildew after harvest,and improve the energy utilization rate of combine harvester,the heat and mass transfer process of rice in the combined harvester lifting screw conveyor were analyzed using CFD-DEM coupled simulation method and experimental method,as well as the drying mechanism of rice in the combined harvester lifting screw conveyor.The main research contents and results are as follows :According to the structural characteristics of the combine harvester lifting screw conveyor,two drying schemes were proposed: the internal heating of infrared heater installed in the screw conveyor center and the external heating of infrared heater installed in the screw conveyor outer tube.Based on the computational fluid dynamics and discrete element method,the CFD-DEM coupling model of two drying schemes was established,and the flow field change heat,the mass transfer and movement process of rice in the screw conveyor were simulated.t,The change of flow field,heat and mass transfer and movement of grain in the screw conveyor were obtained.The effects of two drying schemes on grain drying were compared and analyzed.The results show that the external heating schemes is better than the internal one.CFD-DEM coupling method was used to analyze the influence of different factors on the drying effect of external heating drying scheme.The results show that the grain temperature rise decreases with the increase of auger speed,hot air speed and feeding amount,and increases with the increase of hot air temperature,radiation temperature,auger length and auger diameter;the grain precipitation amplitude decreases with the increase of auger speed,feeding amount and auger length,increases with the increase of hot air temperature,radiation temperature and auger diameter,and first increases and then decreases with the increase of hot air speed;increasing the length and radius of the auger has no obvious effect on the precipitation range;the main factors affecting the drying effect are the auger speed,hot air temperature,hot air speed,radiation temperature and feeding amount.The test bench of external heating schemes was set up and the validation test of simulation analysis shows there is a certain error between experimental results and simulation results,but their change trends are consistent,which indicates the feasibility of studying rice drying based on CFD-DEM method,and the results have certain reference value.Taking the auger speed,hot air temperature,hot air speed,radiation temperature and feeding amount as the experimental factors,the precipitation range and burst waist rate as the experimental indexes,quadratic regression orthogonal combination test was conducted and the regression equations between the two indexes and the five factors were obtained,as well as the primary and secondary factors,influence rules and interaction affecting the experimental indexes.The results show: the influence order of the factors on the precipitation range of rice is as follows: hot air speed,feeding amount,auger speed and hot air temperature;the influence order of the factors on the burst rate is as follows: radiation temperature,hot air temperature,feeding amount,auger speed and hot air speed.The optimization function of design expert software was used to optimize the drying parameters based on the regression equations.The optimized operation parameters are as follows: the speed of auger is 1000 r / min,the temperature of hot air is 60 ℃,the speed of hot air is 6m / s,the radiation temperature is 400 ℃,the feed rate is 1.24kg/s,the precipitation range is 5.78%,and the burst waist rate is 1.49%.The experimental results with the optimized dying parameters show that the precipitation range is 5.45%,the burst waist rate is 1.42%,and the relative errors with the optimization calculation are 5.71%and 4.70% respectively.