| Rice is one of the main crops in China,and ratoon rice refers to the production of a second rice crop in one cropping season developed from regenerating rice tillers from nodal buds of the stubble that was left behind after the first seasonal rice harvest.It can make full use of temperature and light resources as well as save labor and seed.In addition,with high quality,the ratoon rice can help to increase both production and income.At present,the main bottleneck restricting the development of ratoon rice is the high rolling rate of machine harvesting in the first season.Therefore,to reduce the rolling rate and improve the operation efficiency,a double channel full feeding ratoon rice harvester was developed according to the agronomic requirements and biological and physical characteristics of the first seasonal ratoon rice at maturity stage.The working principle of double-channel full feeding ratoon rice harvester was analyzed,and its technical parameters were determined based on the model of machine harvesting and rolling in the first season of ratoon rice.In view of the high rolling rate of ratoon rice harvester and winding blockage due to long straw conveying distance of wide header,a double channel header with shunt function was designed.The germination of ratoon stubble is affected by the straws covering the stubble after been chopped by the tail part of harvester.To solve this problem,a kind of scattered device of broken straws was designed,and the field performance test of the whole machine was carried out.The main research findings include:(1)The biological and physical characteristics of ratoon rice in the first harvest season were studied.Through the study of three typical rice varieties,namely Huanghuazhan,Fu'e'you 6981 and Fengliangyouxiang No.1,it was found that mostly,the plant spacing was300mm and the row spacing was 150mm in the first seasonal ratoon rice;the plant height of in the first season at maturity was about 1100mm;the moisture content of fresh stem was about 70.45%,the moisture content of grain was about 22.61%,and the average outside diameter of stem above 350mm stubble was 3.72mm.The results showed that the bending load,shear force and tensile force decreased with the increase of stem position.The maximum average bending load was 4.64N,the maximum average shear force was 142.84N,and the maximum average tensile force was 201.54N;the bending strength,shear strength,tensile strength and elastic modulus of the stem increased with the increase of the stem position.The maximum average bending strength of the stem was 12.38MPa,the maximum average shear strength was 8.62MPa,the maximum average tensile strength was 24.67MPa,and the average elastic modulus was 25.45MPa.These data serve as an important parameter basis for the working parts design,straw modeling and simulation of the ratoon rice harvester.(2)The overall scheme of ratoon rice harvester was determined according to the agronomic requirements of machine harvesting in the first season of ratoon rice.Through the analysis of four agronomic requirements of machine harvesting in the first season of ratoon rice,the structure model of double-channel full feeding ratoon rice harvester was built,consisting of a crawler chassis,a header,two sets of symmetrically arranged threshing and cleaning devices and grass throwing device,grain tank and power and transmission system.The overall parameters are as follows:the feeding rate 4.0kg/s,cutting width 3000mm,chassis gauge 1500mm,track grounding length 1800mm,crawler width 400mm,theoretical straight rolling rate 26.7%.The 65k W Xinchai 498bzt engine was selected as the power of the whole machine,and a complete set of mechanical transmission scheme and hydraulic transmission system were also designed.(3)A double channel header was developed,which could shorten the conveying distance of straws,transfer the power of auger,reel and cutter separately,effectively balance power consumption and avoid single side power shortage.Based on the analysis of the speed and stress of the material transported by the two-way screw auger and the requirement of stubble height in the first harvest season of ratoon rice,the inner diameter of the auger was set to be250mm,the height of the spiral blade was 65mm,the outer diameter was 380mm,the pitch was 260mm,and the circumferential angle between the two long spiral blades in the middle of the auger was 180°.In addition,the transmission arrangement of retractable fingers was determined.According to the rice feeding process of the reel,the diameter of the reel was700mm,the rotational speed was 45r/min,and the installation height of the reel shaft relative to the cutter was 600mm.(4)The strength analysis and structure optimization of crawler chassis was carried out.According to the determined chassis parameters,the structure size of chassis running system,transmission system and gearbox type were further refined.On the basis of the structure layout of the whole machine,the frame was designed and statically analyzed.It was found that the weak parts were mainly where the grain tank was installed on the cantilever beam,where the threshing and cleaning device was installed on the cantilever beam and the support beam of header lifting cylinder.After optimization,the maximum stress of the frame was213.93MPa,which was less than the material yield limit of Q235,and the maximum deformation was only 1.8mm,which meet the design requirements.The parameters of threshing and cleaning device were designed.Rod toothed longitudinal axial flow threshing drum,fan plus vibrating screen cleaning mode and chain harrow conveyor were adopted.The effective volume of grain tank was designed to be 1.5m~3.(5)In this paper,a new type of straw throwing device was designed for double channel feeding ratoon rice harvester,and the performance of straw crushing and throwing was analyzed.The straw crushing and scattering device mainly included the main box,straw guide tail plate,moving knife roller,fixed knife group and other parts,which could crush and scatter the straws thrown out by the threshing roller to the rolling area.The process of crushing and scattering was divided into straw crushing process and straw scattering process.The dynamic analysis of straw crushing process was carried out,and the main factors affecting straw crushing effect were determined.According to the different space position when leaving the blade,the straws were divided into up throwing,flat throwing and down throwing.The kinematics analysis of the space track of the straw in the three kinds of scattering conditions was carried out,and it was concluded that the scattering characteristics of the straw were affected by its initial position,initial angle and initial speed.The dynamic analysis of the straw guiding performance of the straw guide tail board showed that the angle and size of the straw guide plate had a great influence on the scattering performance of the straw.(6)The structure parameters design and simulation analysis of the grass crushing device were carried out.The rotation speed of the cutter roll was 2800r/min,the blades on the cutter roll were arranged in double helix,and the rotation direction of the cutter roller of the left and right straw crushing devices was opposite.The modal analysis of the cutter roller will not produce resonance.Based on EDEM,the simulation analysis of straws spreading process was carried out.The results showed that the optimal parameters combination of straw guide tail plate was 45°between the straw guide cover plate and the vertical direction,the height difference between the tail of the guide plate and the straw outlet was 200 mm,the inclination angle of the inner side board was 0°and the angle of the outer side board was 35°and the throwing qualified rate was 72.2%.The results showed that the qualified rate of straw throwing was 93.6%in the bench test,95.2%in the field test,and 91.6%in the crushing length,which meet the requirement of harvest.(7)Field performance test and yield measurement of ratoon rice harvester with double channel feeding were carried out.The field test showed that the operation speed could reach0.83m/s,the detection value of feeding amount was 4.6kg/s,the total loss rate was 2.1%,the impurity content rate was 0.4%,and the crushing rate was 0.2%,which are in line with the standard requirements.Compared with the ordinary harvester,the crushed straw of the double-channel full feeding ratoon rice harvester was basically scattered to the track rolling area,and the qualified rate of straw throwing reached 95.2%,while the straw of the control group was evenly scattered and covered with a large amount of straw on the stubble.The ratio of stubble area after harvest of double-channel full feeding ratoon rice harvester was larger than that of the control group.The direct rolling rate of two harvesters was 26.7%and45%respectively.That is,the double-channel full feeding ratoon rice harvester can reduce the rolling rate by 18.3 percentage points,which has a significant advantage.The yield test of ratoon season was carried out.The yield was 401.1kg/mu in the ratoon season.In the harvesting area of common harvester,the yield was 323.8kg in ratoon season.The double-channel full feeding ratoon rice harvester could increase the yield by 77.3kg per mu,or 23.9%,compared with common harvesters. |
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