Theoretical And Experimental Investigations Of Cereals Threshing And Separation On Tangential-Longitudinal Axial Device

A threshing and separation device is the core component of combine harvester. The threshing and separation performance of the device directly decide the work performance of the combine harvester. So, the study of threshing and separation performance is the key step to improve harvesting performance. In this paper, stalk motion model was researched when the threshed stalk was movement in the threshing and separation space, and the optimal structure scheme of tangential-longitudinal axial device was exploded to improve the conveying, threshing, separation performance of threshing and separation device, which based on the structure characteristics of tangential-longitudinal axial device. Threshing and separation model of the tangential-longitudinal axial device was established to learn the optimum working parameters of the device with high efficiency and high performance threshing for wheat and rice, by the experimental exploration of relations between threshing and separation device and the harvesting performance influence factors. These were of great scientific significance and practical value to improving the technical level of tangential-longitudinal axial combine harvester, to accelerate the upgrading of products, to promote China’s harvest machinery industry technical progress. Based on summarizing the research status at home or abroad and the existing research work of project group, the related research works were carried out by the combined method of theoretical research, numerical simulation and experimental verification. The major research work is as follows:Based on the grain characteristic, the variable structure tangential axial drum and longitudinal axial drum were designed. Five thresher bars were designed for the tangential axial drum and longitudinal axial drum to thresh rice and wheat crops. The probabilistic model of threshing and separation with five thresher bars were estabilsed. The best combinations of thresher bars on the longitudinal axial drum were obtained by calculating the probabilistic model. The material flow model of tangential-longitudinal axial structure was established to derive the motion model of rice and wheat crops, which were from tangential axial drum to the longitudinal axial drum. The variable mass model of threshing and separation was established for the tangential-longitudinal axial structure, and the check experiment was executed on the constant mass and variable mass.Threshing and separation test with multiple factors and conditions were executed for the experimental factor of drum rotational speed, threshing clearance, thresher bar, arrangement of thresher, and the thresher bar tooth spacing. The mathematical models between main influence factors and performance index of unthreshing grain loss, unseparation grain loss, broke grain loss and threshing power, were executed for tangential-longitudinal axial structure. Significant level of influencing factors to the performance index was studied. The evaluation methodology of multiple factors and multiple targets were deviced based on the influencing factors. Rice threshing and separation performance test and grain distribution test were executed and studied by the adjustable length of longitudinal axial drum designed by ourselves, on the test bench of tangential-longitudinal axial device. The threshed grain distribution equation of longitudinal axial drum was established to calculate the length of longitudinal axial drum. The length of longitudinal axial drum was optimization to learn the optimal length value verified by the rice threshing and separation test, based on calculating the best guide angle of longitudinal axial drum cover plate. The above researches provide the design basis of longitudinal axial drum.The structure and working parameters of tangential-longitudinal axial device was optimization studied by the method of theoretical analysis and experimental verification. The combination mode of thresher bars on the tangential axial drum and longitudinal axial drum were verified by threshing and separation performance testing with7kg/s rice harvesting. Three main influence factors of drum threshing speed, threshing clearance, and the thresher bars tooth spacing were studied on the rice test with the feed rate of7kg/s. The threshing power and total grain loss rate were handled by the normalization method with the single factor test results. The parameters infecting the threshing and separation performance were studied by regression analysis and significance lest of regression effect. Optimum parameters and their confidence interval were forecast and test verified by controlling the threshing and separation performance.The threshing and separation torque values of longitudinal axial drum were collected with torque sensor, when the threshing and separation test was executed with the feed rate of6kg/s～8kg/s on the threshing and separation device. The performance index of threshing and separation power and grain total loss were learned by wheat bench test on the tangential-longitudinal axial device. The feasible regions of threshing and separation optimal performance index were studied by the plural amplitude calculation method. Vector index angle tangent value of threshing and separation performance were calculated to learn the best structure and motion parameters, by changing threshing and separation power and grain total loss into plane geometry vector index.Distribution characteristics and distribution regularity of separation mixture under longitudinal axial drum were determined and analysis, by the wheat threshing performance test with feed rate of6-8kg/s on the threshing and separation device. Threshing and separation matrix equation of unthreshing grain rate, threshing and separation impurity rate, and threshing and separation grain rate was established, based on distribution characteristics and distribution regularity of separation mixture. The above researches provide the selection of working parameters and design of drive structure for tangential-longitudinal axial combine harvester. The above optimized results were transferred to tangential-longitudinal axial combine harvester to test the harvesting performance of the threshing and separation device in the field rice harvesting.