Design And Mechanism Research On Threshing And Separation Device For Southern Soybean Combine Harvester

Southern China as the main soybean producing areas,the temperature and the humidity of air during soybean harvest were high,led to the ratio of soybean grass to grain and the proportion of immature pods were high.The adaptability of the existing threshing and separation device of soybean combine harvester was poor to the characteristics of Southern soybean,led to the crushing rate and loss rate in the process of machine harvest were high.In order to develop a combine harvester suitable for soybean characteristics in Southern China,need to improve the working quality of threshing and separation device.The commonly used threshing and separation device of longitudinal axial flow combine harvester was used to the research object,and designed a new threshing and separation device to reduce the crushing rate,loss rate and impurity rate in the process of harvester.Through theoretical analysis and finite element simulation,the feasibility of the designed threshing and separation device to improve the working quality of combine harvester was verified,Finally,the structure and working parameters of the designed threshing and separation device were optimized and experimented through bench experiment and field experiment.The main research contents and results of this paper are as follows.（1）Ressarch on threshing and separation mechanismAnalyzed the changes of the structure and working parameters of the threshing cylinder and their effects on the changes of material energy and deformation in the threshing room.It was found that the kinetic energy and the equivalent shape variable after the grain and the material collision with the rod teeth were greater.The greater the cylinder speed and the number of collisions between the material and the threshing teeth,the greater the energy accumulated in the material,while the separation quality of the grain was affected by the kinetic energy and speed direction of the grain.The results of the study provided theoretical and data support for the subsequent analysis of the changes of evaluation indicators.（2）Design and performance experiment of segmented differential threshing systemAccording to the characteristics of soybean in the harvest period in Southern China,designed a segmented differential threshing cylinder with adjustable speed difference,and the working quality of the designed differential threshing cylinder and the existing single speed threshing cylinder was compared through pre-experiment.The experiment results showed that the type of threshing cylinder suitable for soybean threshing in Southern China was differential threshing cylinder,and the optimal parameter combination:the speed of the front cylinder was 450 r/min,the speed of the rear cylinder was 150 r/min.compared with the traditional single speed threshing cylinder,the crushing rate,unthreshed rate and entrainment loss rate were reduced by 0.47%,0.03%and 0.10%respectively,The experiment results provided a structural and parameter reference for the further study of the threshing and separation device suitable for soybean harvest in Southern China.（3）Design and performance experiment of separating partsA symmetrical adjustable concave was designed,and the mathematical model of the variation of the cross-sectional area of the threshing gap between the symmetrical adjustable concave and the traditional vertical adjustable concave was constructed by using the analytical geometry method,as well as the variation law of the density of the internal material flow and the internal rubbing strength of different concaves.According to the variation law and the field experiment results,the working quality of the symmetrical adjustable concave was better than the traditional vertical adjustable concave.Through the orthogonal experiment,the optimal parameter combination of the symmetrical adjustable concave was determined as follows:the forward speed was 3.3 km/h,the cylinder speed combination was 500/650 r·min^-1,the threshing clearance in the threshing section was 18.7mm,and the threshing clearance in the separation section was 15 mm.In this condition,the crushing rate,unthreshed rate and entrainment loss rate were reduced by 0.46%,0.71%and0.55%compared with the traditional vertical adjustable concave.（4）Performance experiment of complete machineAccording to the structure of harvester,differential threshing cylinder and symmetrical adjustable concave,built a harvest experiment bench.Through the bench experiment,it was found that the distribution of the existing combine harvester didn’t match the air flow field,led to the loss rate and other indicators were high.According to the experiment results,improved the structure of the designed symmetrical adjustable concave,an independently adjustable concave with four concaves whose corresponding threshing clearance can be adjusted separately was designed.Through orthogonal experiment,the optimal parameter combination of threshing and separation device was determined as follows:the feeding amount was 3.2 kg/s,the length ratio of front and rear cylinders was 1:2,the rotating speed of front cylinder was 406 r/min,the rotating speed difference of cylinder was 143 r/min,the left front threshing clearance was 22.1 mm,the front threshing clearance difference was 6.7mm,the left rear threshing clearance was 18.1 mm,and the rear threshing clearance difference was 10 mm,In this condition,compared with the existing threshing and separation device,the crushing rate,loss rate and impurity content were reduced by 0.56%,0.52%and 0.65%respectively,which verifies the superiority of the designed threshing and separation device of soybean combine harvester in Southern China in threshing performance.