Structural Design And Experimental Study Of Millet Header With Low Loss Rate

Millet is the main small grain cash crop in China,with a planting area of about20 million mu.At this stage,it is mainly harvested manually,and the low mechanized harvest rate has become an important reason to limit the further expansion of millet planting scale.In recent years,in order to improve the mechanized harvest level of millet,many manufacturers have modified the rice wheat combine harvester to meet the harvest demand of millet.According to the investigation,the modified millet combine harvester has some problems such as difficult feeding and high total grain loss rate during field operation.The header loss accounts for about 40% of the total loss rate.The main reasons for the large header loss include: 1)The high growth height of millet in the mature stage and the large sliding loss caused by the insufficient depth of the header of the traditional grain combine harvester.2)After the millet is mature,the weight of spike head accounts for a large proportion of the total weight of the plant itself,resulting in the interweaving of spike head,stem,leaf and stem,and the serious dragging in the ordinary divider,resulting in large dragging loss.3)At maturity,the spike head of millet is heavy and tilted and bent forward as a whole.Due to the improper installation of reel position,the effect of reel is poor.4)Because the diameter of the feed auger of the header is too small,the plant is wound on the auger,resulting in the blockage of the header.In order to solve the problem of high header loss rate of traditional grain combine harvester when harvesting millet in the field,it is necessary to develop a low loss rate header device suitable for millet harvest,so as to further improve the mechanization level of millet harvest.The main research contents of this paper are as follows:1)Field investigation and experiment.The morphological characteristics of millet plants were measured and the biomechanical characteristics were studied.The morphological characteristics such as the length of millet plants,natural height,center of gravity height,spike head length and spike width difference at maturity were mathematically counted,and the mechanical characteristic parameters such as tensile,bending and shear of millet plants were measured by using relevant instruments and equipment,so as to provide data support for the design of millet header.2)Movement process analysis of header and structural design of key parts.According to the morphological characteristics and biomechanical characteristics of mature millet plants,the overall and key components of the header of millet combine harvester(such as header depth,header auger,divider,cutter and reel)are designed,the header layout is optimized,and the relative position relationship of cutter,reel and header auger in the header system is determined.3)Kinematics simulation analysis of reel.The three-dimensional modeling of the reel is carried out by using Solid Works software,and the kinematic simulation analysis of the reel is carried out by Recur Dyn software to obtain the motion track of the reel rod and the speed curve and displacement curve of the elastic tooth end of the reel,so as to verify whether the reel structure can meet the needs of millet reel.At the same time,on the premise of the best function degree of the reel,it is concluded that the reel speed ratio when harvesting millet should be between 1.5-1.6,which provides a reference for determining the range of reel speed ratio when harvesting millet by combine harvester.4)Finite element simulation analysis of header frame.The three-dimensional modeling of millet header frame is carried out by using Solid Works software,and the finite element simulation analysis of millet header frame is carried out by ANSYS software.Firstly,the computer modal analysis of the millet header frame is carried out to study the stability of the header frame structure and then the mechanical simulation analysis of the header frame is carried out to verify the strength and stiffness of the header frame.At the same time,the experimental modal analysis of millet header frame is carried out,which is verified with the data obtained by computer modal analysis,so as to improve the accuracy of modal analysis results.5)Field harvest test verification.After the processing,manufacturing and preliminary commissioning of the millet header are completed,the millet header is installed on the millet combine harvester for field test.The single factor and multifactor field experiments were carried out with the forward speed of the millet combine,the speed of the reel and the vertical height of the reel central axis relative to the cutter,and the best parameter combination of the header working parameters was obtained.The test showed that the header loss rate of the millet combine was 0.49%,which was lower than the national industry standard level.