| Development of silage feed is an effective measure to alleviate the shortage of livestock feed in autumn and winter.Silage corn and feed rape forage are widely planted in the Yangtze River Basin in China.Silage corn,cut and rolled into strips,is the main source of silage feed,while the fresh and tender stems of winter rape have high biomass yield and can be an important supplement to silage feed after moderate cutting.In response to the problem of the single shredding form of existing silage harvesters,which is difficult to meet the differential requirements of corn coarse and hard straw shredding and moderate shredding of feed rape crispy and tender plants,a material chopping and throwing device for both silage corn and feed rape is proposed based on the current situation of a large number of combine harvesters in various regions.The device is mounted on a crawler type mobile chassis and can be used to complete the harvesting,chopping,throwing and collecting of silage corn or feed rape.The overall structure and process flow of the machine were explained based on the harvesting requirements for silage corn and feed rape.Key components,such as the double-roller feeding device,the hob-type chopping device,and the straight knife type kneading and chopping device,were designed,and mechanical and kinematic analyses were conducted for the material chopping and conveying process,the structural parameters and working parameters of the key components are determined.Using EDEM simulation,we identified the optimal speed ratio for the chopping and throwing process for silage corn and feed rape,and the transmission ratio of the whole machine was optimized.Based on the simulation optimization experiments results of the chopping and throwing device,the field optimization experiments were conducted.,using evaluation indicators such as the harvesting loss rate and the chopping qualification rate,to analyze the optimal combination of the main technical parameters of the machine.Field experiments were conducted to analyze the optimal forward speed of machine harvesting silage corn and the optimal working parameter combination for harvesting feed rape,using harvest loss rate and chopping qualification rate as evaluation indicators.The main research contents are as follows:(1)The design and parameter analysis of the overall structure and material chopping and throwing device were carried out.(1)A dual purpose material chopping and throwing device for silage corn and feed rape is proposed,which is equipped with a crawler type mobile chassis.Through modular design,the material chopping and throwing device,collection and unloading box replace the threshing,separation,and cleaning device and grain box of the combine harvester,achieving the functional reorganization of the entire machine;The material chopping and throwing device includes key components such as a double-roller feeding device,a hob-type chopping device,and a straight knife type kneading and chopping device.It is designed as a dual channel structure,and the material flow path is changed by adjusting the outlet position of the hob-type chopping device to meet the requirements of shredding silage corn and feeding rape respectively.(2)A double-roller feeding device was designed,and the force analysis of the feeding device during material feeding was conducted.Based on the thickness change of the material flow,the feeding roller radius was determined to be 55 mm,and the feeding roller speed range was 521～868r/min.(3)The structure design and parameter analysis of the hob-type chopping device were carried out.The chopping drum and moving blade structure,chopping motion process,and material conveying trajectory were analyzed.The radius of the moving blade trajectory was determined to be 250 mm,the forward angle of the moving blade installation was 40～48°,the inclination angle of the rolling cutter was5°,the chopping and sliding angle was 15°,the number of moving blades was 18,and the chopping drum speed range was 647～991r/min.The installation height of the fixed knife is 70 mm,and the gap between the moving and fixed knife is 0.4～1 mm.(4)The force analysis of the straw kneading and chopping process of the straight knife type kneading and chopping device was carried out.The blade arrangement was determined to be symmetric,and the speed range of the straight knife cutter was 1833～2200r/min.(5)The transmission line of the entire machine was designed,and the power of the machine was taken from the crawler-type walking chassis.(2)The simulation experiment of the chopping and throwing process of the material chopping and throwing device was carried out based on EDEM.(1)The discrete element particle bonding model of corn straw and rape stem was established using EDEM discrete element simulation software,and three-dimensional models of silage corn chopping and throwing device and feed rape chopping and throwing device were established.(2)The single factor discrete element simulation experiment and orthogonal optimization simulation experiment were conducted on the process of material chopping and throwing silage corn using the feeding roller speed,chopping drum speed,and straight blade cutter speed as experimental factors,and the throwing pass rate and breakage rate of corn straw as performance evaluation indicators.The optimal working parameter combination of the silage corn chopping and throwing process was obtained as follows: the feeding roller speed is 659.46r/min,and the chopping drum speed is 959.46r/min,The speed of the straight blade cutter is 2159.46r/min,and under this parameter combination,the theoretical maximum throwing qualification rate is 91.71%,the maximum breaking rate is94.14%,and the theoretical optimal speed ratio of the three is 1:1.45:3.27.(3)The single factor discrete element simulation experiment and orthogonal optimization simulation experiment were conducted on the chopping and throwing process of feed rape using the material chopping and throwing device,with the feeding roller speed and chopping drum speed as experimental factors and the throwing and throwing pass rate and chopping length pass rate of rape stalks as performance evaluation indicators.The optimal working parameter combination for the feed rape chopping and throwing process was obtained as follows: the feeding roller speed was 729.68r/min,and the chopping drum speed was629.29r/min,The theoretical maximum throwing pass rate under this parameter combination is 98.98%,the maximum chopping length pass rate is 92.95%,and the theoretical optimal speed ratio of the two is 1:0.86.(4)After comprehensive analysis of the optimal parameter conditions of two material chopping and throwing experiments on the chopping and throwing effect of the other material,the optimal speed ratio of silage corn chopping and throwing is selected as 1:1.45:3.27 as the transmission ratio of each component of the material chopping and throwing device.The transmission ratio and selection of the entire transmission system were determined based on the chassis engine speed,and the prototype processing and trial production of a tracked silage corn and rape dual purpose harvester was completed.(3)Field optimization experiments on the working parameters of the whole machine were conducted.(1)Based on the optimal working parameter range obtained from the simulation experiment of chopping and throwing silage corn and feed rape,the reasonable range of engine speed for silage corn harvesting was about 2000～2600r/min,and that for feed rape harvesting was about 1700～2300r/min.(2)Taking engine speed and machine forward speed as experimental factors,and using the qualified throwing rate and qualified chopping rate as performance evaluation indicators,the field optimization experiment of silage corn harvest was conducted.The optimal working parameter combination of the silage corn and rape dual-purpose harvester for harvesting silage corn was obtained,with an engine speed of 2512.13r/min and a machine forward speed of 0.48m/s.The theoretical minimum harvesting loss rate under the optimal working parameters was 3.12%,and the highest chopping rate was 99.27%.(3)Taking engine speed and machine forward speed as experimental factors,and using the qualified throwing rate and qualified chopping length rate as performance evaluation indicators,the field optimization experiment of feed rape harvest was conducted.The optimal working parameter combination of the silage corn and rape dual-purpose harvester for harvesting feed rape was obtained,with an engine speed of 1979.31r/min and a machine forward speed of 0.56m/s.Under the best working parameters,the theoretical minimum harvesting loss rate was 5.15%,and the highest chopping length rate was 94.22%.(1)According to the design scheme of the overall transmission ratio of the crawler-type silage corn and rape dual-purpose harvester,the engine speed was controlled at 2600r/min,and the overall forward speed was used as the experimental factor.The harvesting loss rate and chopping qualification rate were used as performance evaluation indicators.A single factor field experiment for harvesting silage corn was conducted,and the optimal overall forward speed of the crawler-type silage corn and rape dual-purpose harvester was obtained at 0.5m/s.Under this parameter,the theoretical minimum harvesting loss rate obtained from the operation is 2.77%,and the highest chopping qualification is 96.61%.(2)Based on the speed range of the shredding drum obtained from the simulation experiment of feed rape chopping and throwing,with engine speed and overall forward speed as experimental factors,harvesting loss rate and chopping length rate as performance evaluation indicators,an orthogonal optimization field experiment for feed rape harvesting was carried out.The optimal working parameter combination for the crawler-type silage corn and rape dual-purpose harvester to harvest feed rape was obtained as follows: engine speed 1979.31r/min,overall forward speed0.56m/s.Under the optimal working parameters,the theoretical minimum harvesting loss rate is 5.15%,and the maximum chopping length rate is 94.22%.During the machine harvesting operation,the material is cut and transported smoothly,the stubble is cut neatly,and there is no obvious blockage.They meet the operating standards for silage corn harvesters and green feed harvesters respectively.(3)A comparative experiment was conducted on the chopping performance of materials.Harvesting silage corn using the machine’s feed rape chopping and throwing harvesting function,and harvesting feed rape using the machine’s silage corn chopping and throwing harvesting function.The results of the two experiments showed that the materials obtained could not meet their respective chopping standards,proving that only one chopping form could not meet the requirements for both silage corn and feed rape,It is necessary to design a dual channel to distinguish between the harvesting function of silage corn and the harvesting function of feed rape. |
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