Study On The Design Of Threshing System Of 4LZ-9L Tangential Longitudinal Axial Flow Wheat Combine Harvester

Threshing device is the core component of wheat combine harvester,with the development of wheat threshing technology,traditional transverse flow and single longitudinal flow threshing technology have some problems such as high loss rate and incomplete threshing under large feeding rate.The longitudinal threshing technology has been widely used in the mainstream models abroad because of its high removal rate,low loss rate and strong adaptability,but the domestic research on tangential longitudinal threshing technology is still in the initial stage.In order to solve the problem of the lack of design research of domestic tangential longitudinal axial flow technology,the following research is carried out in this paper for the tangential longitudinal axial flow threshing system of 4LZ-9L wheat combine harvester,and the main research contents include the following five aspects:(1)Taking the 4LZ-9L tangential longitudinal axial flow wheat combine harvester threshing system as the research object,the structural parameters of the main components of the tangential longitudinal axial flow threshing device were designed and calculated,and based on the calculated results,the 3D modeling of each component was carried out by Solidworks,and the virtual assembly was completed,and the threedimensional model of the tangential longitudinal axial flow threshing system was obtained.(2)The biomechanical properties and geometry of wheat plants were studied with the main wheat variety "Huai Mai 40" in Henan Province,and the physical parameters of the stalk and spike part were measured.The experimental study was carried out for the mechanical properties of wheat stalk and wheat spike as well as the contact parameters between materials,which provided the data basis for the subsequent establishment of a discrete element model of wheat plant.In order to realize the discrete element simulation experiment of wheat threshing system,a discrete element model of thresh-able flexible wheat plant was established by using the Hertz-Mindlin with bonding model and the multi-scale particle aggregation method.The accuracy of the discrete element model of wheat plant was verified by conducting parameter calibration tests on the established wheat plant model.(3)According to the structural characteristics of the tangential longitudinal axial flow threshing system,a tangential longitudinal axial flow threshing test bench was established.The test bench is driven by dual motors and the overall structure is modularized.The test bench includes a cutting table,a conveyor chain harrow,a plate tooth type tangential flow drum and a column tooth type longitudinal axial flow drum,a grid concave plate screen,a threshing chamber top cover,a receiving box,a conveyor belt feeding device and an auxiliary support device.The reliability of the test function and operation of each part of the test bench has been verified through pre-tests,which provides the basis for the design of the tangential longitudinal axial flow threshing system.(4)The research work verified the reliability of wheat plant model application in threshing simulation tests by comparing the results of tangential flow drum threshing simulation tests with those of bench tests,using the threshing rate as the evaluation index.The discrete element simulation test was used to analyze the tangential flow threshing and separation process.The threshing rate of the tangential flow drum was around 16%,which verified the design objective of the tangential flow drum as the main accelerated conveying function.The tangential longitudinal axial flow threshing simulation test was conducted to obtain the movement pattern of the wheat in the threshing device and the mass accumulation distribution of the threshing material and the seeds;the single-factor test was carried out with the entrained loss rate and the threshing clearance as the evaluation index,the feeding quantity and the axial flow drum speed as the test factors,and finally the two-factor three-level orthogonal test was carried out with the entrainment loss rate as the evaluation index,and the drum speed ratio was obtained.The optimum ratio was 554 r/min for the tangential flow drum and895 r/min for the longitudinal axial flow drum.(5)The cumulative distribution pattern of detritus and seeds was studied under the test conditions of 9 kg/s feeding rate,600 r/min cutting drum speed and 900 r/min axial drum speed,and the cumulative distribution pattern of threshing material was obtained by comparing simulation and bench test.A bench test was conducted with the speed ratio of the two drums as the test factor and the entrainment loss rate as the evaluation index,the bench test was carried out with two factors and three levels,and the best ratio of two drums’ speed was obtained by the extreme difference analysis and response surface analysis,the results were that the speed of the tangential drum was 550 r/min and the speed of the longitudinal axial flow drum was 900 r/min,and the entrainment loss rate was the lowest 0.31%,This meets the national and industry requirements.