| The straw chopping device on the rice-wheat-rape combine harvester,as the main machines of returning crop residue to the field,has gradually become the standard configuration of most domestic combine harvester.The straw chopper in the chopping device needs to cut different types of crop straws during operation.Compared with the wheat straws which are easy to cut,the thin,soft and tough rice straws and strong rape straws bring greater cutting resistance to the straw chopper when they are being cut,which leads to poor chopping quality.In addition,the increase of cutting resistance intensifies the wear of the straw chopper,which not only reduces the performance and operational reliability of the knife,but also increases the cutting power consumption of the combine harvester.In order to improve the efficiency of cutting rice and rape straws with straw chopper and reduce the energy consumption of straw chopping device,this paper mainly studies the cutting parts in the straw chopping device of combine harvester,and carries out the design of bionic straw chopper.Based on the straw chopping device of a 4LZ-6.0crawler self-propelled full feed grain combine harvester from World Corporation,and comparative experiments for cutting rape and rice straws of the bionic straw chopper with different types of knives were carried out.The research contents mainly include:(1)Taking the locusta migratoria manilensis as the bionic prototype,which is a common creature in the field with crop stems and leaves such as rice and rape as the main food source,and the mouthparts of locusta migratoria manilensis were observed through the ultra depth of field three-dimensional microscope,and the tooth features with cutting function were inversely reconstructed by image processing.The characteristic models of the left and right teeth of the locusta migratoria manilensis of the straw chopper knives with different cutting blade were designed according to the design parameters of the existing straw chopper knives and the extracted bionic contour curves.(2)In view of the movement mode that the fixed knife and the moving knife support each other in the straw chopper,the force of the straw chopper was analyzed,and the motion model of the moving knife and the fixed knife was established.The motion position and overlapping length between the two knives are obtained by establishing the fixed knife angle and the blade length.In addition,the static analysis of the structure of the bionic straw chopper was carried out to obtain the stress and strain distribution under the loading condition;Based on the discrete element simulation of EDEM,the particle model of rice and rape straw was established to simulate the straw chopper of straw chopping device.The simulation results show that the force distribution of the cutting straw was obtained.Compared with the smooth knife as the fixed knife and moving knife,the force value of cutting rice straw with the right tooth of locusta migratoria manilensis as the moving knife and the left tooth of locusta migratoria manilensis as the fixed knife was reduced by 44.9% and the force of cutting rape straw was reduced by 53.41%.(3)The bionic straw chopper was processed and trial produced,and the cutting force of cutting a single rice and rape straw was tested in the mechanical tester.The results showed that under the condition of the same size of crop straw,the loading speed had a significant effect on the change of cutting force,followed by the sliding cutting angle of the knife,and the support distance had little effect on the change of cutting force;Compared with smooth knife and sawtooth knife,bionic knife can effectively reduce the resistance of cutting stem and reduces the average cutting force of rape stem by 15.58%～24.49%;Compared with the smooth knife,the bionic knife reduces the average cutting force of cutting rice straws by 18.74%～38.23%;In this experiment,the drag reduction effect of bionic knife of the right tooth of locusta migratoria manilensis is better than that of the left tooth of locusta migratoria manilensis as the moving knife with the fixed knife.(4)Further verify the drag reduction effect of the bionic knife under the actual working conditions,cutting bench test and field test were carried out in this study.The results of bench test show that compared with the test group of the smooth knife as the fixed knife and moving knife respectively,the cutting resistance of straw in the test group with bionic knife was significantly reduced,and it is verified that bionic knife combination cutting method has better drag reduction effect than smooth knife cutting method.The maximum cutting peak force of rice straw was reduced by 50.56% and rape straw by 47.10%;In addition,the bench test verifies the above discrete element simulation of the cutting process of rice straw and rape straw.The simulation error is less than 16.21%,which is basically consistent with the actual cutting force.Through the field comparative experiment,it is concluded that when the combine harvester harvests with full cutting width,the straw chopping device of replacing a seventh of the smooth knife with the bionic straw chopper group reduces the power consumption by 5.48% on average compared with the device of the full smooth knife group. |
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