Study On Threshing And Separation System With Adjustable Concave Clearance

According to the different rice yields in different fields,the cutting height and the advance speed of the machine changed,which led to the unstable feedrate during harvesting.A threshing separation device with adjustable concave clearance was developed to adapt to different federate conditions and improve the harvester performance.The main research contents are as follows:(1)On the basis of analyzing the research status of the domestic and foreign combine harvester threshing separation systems,the main factors influencing threshing separation performance and the influence of various factors on threshing separation performance and power consumption were studied.2)Orthogonal test was carried out with the feed rate,concave clearance and cylinder speed as the influencing factors.The unthreshing rate and unseparated rate were used as evaluation indexes.According to the test results,the influence of various factors on the performance index of threshing separation process was analyzed.The feasibility of adjusting the concave clearance and the speed of the threshing cylinder to adapt to different feeding conditions was also analyzed.(3)The material motion in the threshing separation system was analyzed,and the mathematical model of the axial flow threshing separation device with tangential feeding was established by using the probability theory.The coefficients were constructed as a function of the speed of the threshing cylinder,the feed rate,and the concave clearance.The mathematical relationship between the main factors influencing the performance,the cylinder speed,feed rate,concave clearance,the performance evaluation index,and the unseparated rate were determined.Based on the kinetic analysis of the threshing separation process,a mathematical model of the cylinder speed,feed rate and concave clearance on power consumption was established.(4)The structural design of the threshing and separation device with adjustable threshing gap and the main structural parameters of the device were designed.An innovatively sized barrel was made available.The structural design and key technical parameters of the main components of the threshing drum,gap adjustment mechanism,gap control mechanism and the threshing gear bar were calculated.The kinematics and dynamics analysis of the gap adjustment mechanism was carried out to determine the mathematical relationship between the adjustment angle of the adjustment sprocket and the amount of clearance adjustment,and the required adjustment torque.(5)The experimental test was carried out by using the designed threshing and separation device.The unthreshing rate and unseparated rate and the threshing power were used as performance evaluation indexes.The regression test was carried out with the cylinder speed,feed rate and concave clearance as performance influencing factors.According to the test results,the undetermined coefficients in the model were numerically calculated.The reliability of the model was verified by experiments.The test showed that the relative error between the theoretical and actual values of the unthreshing rate of the model was 8.23%,and the relative error between the theoretical and actual values of the unsparated rate was 2.90%.The relative error between the theoretical and actual power consumption was 1.62%.Through the single factor experiments,the influence of various factors on the threshing and separation performance and power consumption was analyzed by mathematical model.(6)A mathematical model was used to predict the orthogonal test value,and establish a comprehensive performance evaluation system for the performance of the threshing and separation device through normalization.The optimum concave clearance and cylinder speed that should be matched for different feed rate were optimized.It provided parameters for the feeding rate adaptive to feed-adaptive degranulation separation system design.