Design And Optimization Of Harvester Header With Hot Air Drying Rice

In order to decrease the clogging of conveyor,threshing device and sorting device,and the additional losses caused by wet straws entrainment of combine harvester while harvesting the high humidity rice in rainy or frog days,improve the thermal efficiency and utilization rate of the combine harvester,and reduce the mouldy loss of rice,a new technique reuses the waste heat of the harvester to generate hot air,and import the hot air into the header and rice conveyor of the harvester to dry the rice before threshing was proposed.A series of studies have been conducted on the use of hot air to dry rice at the combine harvester header.(1)Based on the theory of heat and mass transfer of rice and the calculation of waste heat recovery of internal combustion engine,the feasibility analysis of waste heat of harvester before desiccation of rice was carried out.The overall scheme of the integrated drying device of the header was analyzed,and a header with hot air cavity at the bottom of the main body of the header was designed,and the effect of installing a diversion cover on the drying process of rice was compared with that without diversion cover by simulation,and the scheme without diversion cover was considered to be better.(2)The coupled CFD-DEM method was used to establish a simulation model of the rice drying process.The model was used to analyse the effects of four factors,namely the rice feeding quantity,the initial moisture content,the hot air velocity and the hot air temperature,on the magnitude of rice precipitation using the quadratic orthogonal centre-of-rotation combination test method.The results show that the four selected factors all have a highly significant effect on the rice precipitation magnitude,and the order of influence is: rice feeding quantity > initial moisture content > hot air temperature > hot air velocity;the rice precipitation magnitude decreases with the increase of rice feeding quantity and rice initial moisture content,and increases with the increase of hot air velocity and hot air temperature;in the selected level range,the optimal drying conditions are: rice feeding quantity is 100 g,hot air velocity of 6 m/s,hot air temperature of 150°C and an initial moisture content of 20%,where the maximum precipitation magnitude of1.541 % is achieved.(3)Using the rice drying process simulation model,the correlation equations between the hot air velocity,hot air temperature and drying time and the magnitude of rice precipitation were obtained,and the graded drying design and hot air flow distribution were carried out for the drying area of the header according to the different movement times of the rice in each area of the header,and the effects of different tilt angles of the air inlet,different porosity of the porous plate and the diameter of the air inlet on the hot wind flow field were obtained.The optimized parameters for the drying area of the header are:the tilt angle of the air inlet is selected as 110 °,the porosity of the porous plate is selected as 18.78% and the diameter of the air inlet is selected as 120 mm.(4)A test bench was built to verify the simulation analysis of rice drying process based on CFD-DEM,and the simulation results were compared with the experimental results.The results show that although there is a certain error between the numerical simulation results and the experimental results,the overall change trend of the two is consistent,which verifies the feasibility of using the coupled CFD-DEM method for the numerical simulation of rice heat and mass transfer process.