| Rice straw returning is an effective measure to ensure food security and improve soil fertility.With the development of mechanized field returning technology,the mechanized ditch buried field returning technology has gradually been analyzed and studied by experts and scholars.The technology of rice straw mulching and returning to the field started late and the research is relatively shallow.At this stage,experts and scholars only focus on the integrated configuration of the whole machine.There is less research on the design of key components.In addition,most of the developed mulching and returning machines have poor trenching effect and stability of ditch type,which cannot meet the requirements of stable straw entering the ditch and burying and covering the soil,resulting in difficult or poor follow-up operations,It affects the operation performance of the whole machine.The ditching device is the most important part of the rice ditching and returning machine,and its ditching performance will directly affect the operation effect and returning rate of the machine.According to the form of trenching,the trenching devices are mainly divided into spiral type,ploughshare type,disc type and chain type trenching devices.Among them,the chain type trenching device has become the preferred new type of trenching device at home and abroad because of its high efficiency and applicability.Therefore,to improve the technology and research and development of rice straw mulching and returning machine,it is urgent to carry out the design and research of rice straw mulching and ditching device.Based on the comprehensive analysis of the above research background and key issues,this study,by reviewing the research status of relevant trenching machines and chain trenching devices at home and abroad,aimed to solve the key core problems of rice straw trenching devices,combined with theoretical analysis,numerical simulation,processing trial production and field experiments and other methods and means,carried out innovative design and optimization research on rice straw trenching devices,Improve the mechanization level and technology of rice straw mulching and returning to the field,so as to provide theoretical support and technical reference for the innovative research and development and optimal design of the trenching device of rice straw mulching and returning to the field.The main contents are as follows:(1)Analysis and design of deep buried trenching deviceBased on the comprehensive analysis of the structural characteristics and existing problems of the ditching device for rice straw ditch burying and returning,a deep buried ditching device and key components suitable for rice straw ditch burying and returning machine were optimized by using the chain ditching form.The overall structure,working principle and main parameters are systematically described.According to the sine exponential function and the form of curve expansion line,the side cutting edge curve and tangent cutting-edge curve of type I circular arc grooving cutter and type II circular arc grooving cutter are designed,and the unsymmetrical array configuration of right-angle grooving cutter,type I circular arc grooving cutter and type II circular arc grooving cutter is constructed.The theoretical mechanical analysis method is used to analyze and calculate the motion parameters of the deep buried trenching device,and the required transmission power of the trenching device is 9.36 k W.At the same time,the force analysis of the soil particle kinematics during the trenching process is carried out,and the working parameters that affect the trenching performance of the trenching device are the forward speed v_x and the driving wheel speedω、Horizontal inclinationθAnd ditching cutter structure dimensions.The three-dimensional model of the ditching device is drawn by Creo 6.0 software,which provides a basis for the subsequent numerical simulation,prototype processing and field test.(2)Dynamic characteristics analysis of deep-buried trenching deviceThrough the research and study of the absolute node coordinate method and the system dynamics equation in the basic theory of multi-body dynamics,the dynamic behavior characteristics of the deep-buried trenching device are analyzed and studied based on the Recur Dyn multi-body dynamics simulation software,and the structural stability and motion stability of the trenching device during the operation process are explored.The model is simplified based on the 3D model,and the corresponding condition constraints and motion forms are added to the model,so that the deep-buried trenching device can run more accurately and quickly in the Recur Dyn software.According to the change rule of the angular velocity,angular acceleration and stress of the driving sprocket and the driven sprocket during the movement of the deep-buried trenching device,the simulation results show that the amplitude of the impact vibration phenomenon of the driving sprocket and the driven sprocket during the operation is small,and the stress condition is basically the same,and the impact on the chain drive system and the overall structure is small,and the trenching device operates stably.When analyzing the motion speed of the chain link in X,Y and Z directions,it was found that the motion speed of the chain link in X direction changed more complex,and the changes in Y and Z directions were basically the same and showed the same law,which had less impact on the transmission system.Therefore,more attention should be paid to the influence of the motion speed of the chain link in X direction on the stability of the entire transmission system.Through the analysis of the simulation results of the driving torque of the driving sprocket,it was found that,the maximum driving torque required by the driving sprocket is 8560000 N*mm.The overall structure design of the deep-buried trenching device is reasonable,and the transmission system is stable during operation.(3)Simulation Analysis of Operation Process of Ditching Device Based on MBD-DEMCombined with the multi-body dynamics analysis software Recur Dyn and the discrete element simulation software EDEM,the numerical simulation analysis of the trenching process test and the single factor test of the trenching device was carried out.By simplifying the three-dimensional model of the actual trenching device,the multi-body dynamics analysis software Recur Dyn is used to simulate the state and motion constraints of the actual field operation of the trenching device.The discrete element analysis software EDEM was used for simulation analysis to explore the trajectory and impact point of soil particles in different locations during ditching;According to the different movement rules of soil particles in the trenching process,it is divided into disturbance stage,throwing stage and falling stage for analysis.The movement state of soil in the three stages is clarified,and the curve fitting of soil velocity in different stages is carried out.The combined velocity of soil particles has a certain correlation with the trenching operation time,R~2 is greater than 0.7.The single factor simulation test results show that the stability of the groove decreases with the increase of the forward speed,the increase of the driving wheel speed and the decrease of the horizontal inclination when the groove section is taken as the test index;When the maximum values of the horizontal,vertical and lateral resistance of the three types of trenchers are taken as the test indicators,the change of the maximum values of the three resistance of the right-angle trencher is not the same as the change of the arc trencher,but the maximum value of the horizontal resistance is generally greater than the maximum value of the vertical resistance and the maximum value of the lateral resistance,and the horizontal resistance is the most important factor of power consumption.(4)Field test of deep buried trenching deviceTo determine the rationality of the deep buried trenching device and the accuracy of simulation analysis,solve the most effective working parameter combination,trial produce and process the deep buried trenching device,integrate and configure the rice trenching prototype,and carry out field test research with John Deere 904 tractor.The forward speed,driving wheel speed and horizontal inclination analyzed in the previous stage were taken as test factors,and the stability coefficient of the ditch depth and the consistency coefficient of the ditch bottom width were taken as test indicators.The single factor and multi factor orthogonal tests were carried out,and the test results were processed using the Design Expert 8.0.6 data analysis software.The fixed factors of simulation test are selected for verification test.The test results show that when the forward speed is 0.54m/s,the driving wheel speed is 266r/min,and the horizontal inclination is 30°,the ditching stability is the best.The stability index of ditching depth and the consistency index of ditch bottom width are greater than 96%,meeting the requirements of paddy field ditching stability.At the same time,combined with the analysis of the previous single-factor and multi-factor test results,the power consumption of the trenching device under different test factors is tested and verified by the two-factor five-level quadratic orthogonal rotation center combination test.The test results show that the driving wheel speed and forward speed have an interactive effect on the power consumption.When a certain experimental factor is fixed,the power consumption increases first and then decreases. |
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