| Corn combine harvester for reaping both corn stalk and spike(CHRSS)is essential for taking full usage of corn.Header is the most important part of the CHRSS.However,there are some issues need to be solved,such as unsatisfied green and yellow feeding requirement due to poor cutting quality.A new type of header for the CHRSS was designed based on analyzing the construction of existing domestic and foreign headers of the CHRSS.Theoretical analysis,simulation and field tests were made for the produce of its main components and a new type of header was thus manufactured and validated by farm tests.The main research contents and conclusions are as follows:A new kind of header was designed,which cut corn plant by reciprocating cutter,gripped and delivered corn plant by gripping chain,cut up by rollers,picked corn cob by plate and pulled corn stalk by ejector roller,cut corn stalk by transversal roller cutter,transported corn ear and break stem by dragon conveyor.Working principles of its main components were analyzed,and mathematical models between its structure and motion parameters were built.Physical parameters and bending characteristics of corn plants were measured.Radial compression and shearing characteristics of corn stalk were conducted.Mathematical relations among physical parameters and equation between deflection angel and measure height were studied.Force-displacement curve of radial compression and shearing were gained.Maximum force of radial compression and shearing tests from root to head were recorded.Multi-body dynamics and analysis software RecurDyn was utilized to build corn plant and gripping-cutting-delivery rigid-flexible simulation model and analyze corn plant cutting and gripping process.Effects of horizontal distance between reciprocating cutter and gripping point and ear growth direction on gripping and transporting performance were studied.Simulation results showed that:the horizontal distance between reciprocating cutter and gripping point of gripping chains must satisfy to grip first and then cut.Finite element analysis software ANSYS/LS-DYNA was employed to build corn stalk and cutter simulation model and analyze corn stalk cutting process.Influences of cutting knife angle,chopper rotating speed and stalk amount on movement of break stems and connect force between transversal chopper and corn stalk were investigated.Simulation results indicated that:cutting force between transversal chopper and corn stalk had a tendency to increase first and then decrease with the increase of cutting rake angle,and was minimum with cutting rake angle of 53°.The cutting force increased rapidly,when chopper rotating speed was more than 1534 r/min.Divider,grippign-cutting-delivering device,ear picking and stalk pulling device,cutting up rollers,transversal chopper and corn ear and break stem conveyor were designed and manufactured.In order to get the optimum of structure and working parameters,Box-Benhnken Design(BBD)response surface method was used to design the field experiments.An orthogonal rotary combination experiment was conducted with the angle of gripping chain,the teeth number of sprockets in enter shaft,the horizontal distances between reciprocating cutter and the nip point of gripping chains and the working speed of com combine harvester as four independent factors,as well as loss rate of corncobs,maximum offset of x axis and y axis as three dependent indices.The height of 1.2 m in corn straw was signed by a variety of colorful paper tape.And two high speed cameras were utilized to shoot the motion of mark point.ProAnalyst motion analysis software was applied to get the maximum offset of x axis and y axis.Design-Expert software was employed to analyze the test results,mathematical equations and influences between independent and dependent factors were gained.The results indicated that at the angle of gripping chain in 200,the teeth number of sprockets in enter shaft in 22(corresponding gripping and delivering chain speed in 4.54 m/s),the horizontal distances in 22 mm as well as the working speed of corn combine harvester in 1.30 m/s,the gripping and delivering device showed optimal performance with loss rate of 0.4%and maximum offset of x axis of 23.99 mm.BBD response surface method was also employed to design the corn stalk cutting experiments.Aiming at studying the effect of the chopper's parameters on picking and smashing performance,an orthogonal rotary combination experiment was conducted with the working speed of corn combine harvester,the fixed angle of cutting knives and rotating speed of stalk chopper(SC)as three independent factors,as well as broken rate and loss rate of corn kernels,average length and geometric standard deviation of smashed corn stalk as four dependent indices.Parameters optimization showed that when working speed of com combine harvester was 1.35 m/s,the fixed angle of cutting knives was 52°,rotating speed of SC was 1350 r/min,the device had optimal performance with loss rate of corn cob in 1.0%,broken rate of corn kernels in 1.34‰,loss rate of corn kernel in 7.46‰,average length in 30.67 mm,and geometric deviation in 1.29.Seven types of cutting up device were manufactured and compared,high-speed cameras were used to observe the experimental procedure.Observation results revealed:panel didn't have cutting up ability,but cutting up roller had,the third roller is necessary to cut up and feed.On the basis of the optimal setting of the movement parameters and structural parameters,the header was manufactured,consisted of motion transfer system,hydraulic control system and mechanical structure as above mentioned.4YJ-4 corn combine harvester was employed to hang the header to take field trials,the results indicated this header had less corn ear loss and less length and more uniform of break stem could reap both com stalk and spike with the working speed in the range of 4 km/h and 6 km/h and the row distance between 550 mm and 680 mm,the break stem could be used as forage directly.Field experiments were carried out to obtain theoretical models for the angle and length of cut stems,as well as the conveying efficiency of broken stem conveyor. |
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