| Plastic film is a crucial agricultural means of production.As it serves functions like warming and moisture retention,which can effectively improve crop yield and quality,it has made vital contributions to ensuring national food security and the effective supply of major agricultural products.However,heavy use and light recycling result in the problem of residual pollution of farmland plastic film rising.And plastic film has also evolved from a"white revolution"to a"white pollution."Research shows that it is hard to degrade in the soil and then severely affects the ecological environment of soil,crop yield,root growth,and agricultural operations,becoming an outstanding problem that restricts the green development of agriculture in China.That can be solved by the mechanized residual film recycling technology in an essential way.Most of the existing residual film recycling equipment is mainly based on surface residual film recycling equipment after autumn,while there are few pre-sowing residual film recycling equipment.Therefore,this article focuses on the problems of low residual film pickup rate,difficult detachment of the prototype,and serious soil blockage in the pre-sowing residual film pickup machine designed by the research group in the early stage.Specifically,we designed an innovative design of a seeding residual film recovery machine based on the arc-shaped toothed drum structure,determined the structural and working parameters of the machine and its key components;mainly conducted the dynamic analysis of the operation process of the machine;established mathematical models for each key task stage;And finally clarified the impact of various operation parameters on the residual film pickup rate and film wrapping rate.The main research content and conclusions are as follows:(1)The study of the characteristics of residual film and soil materials in farmland before sowing was conducted.First,this thesis measured the retention of residual film in Shihezi,Xinjiang.That included the average residual amount reached 272.00 kg/ha,the distribution coefficient of film residue in the 0?150 mm cultivated layer reached 65%;the mass ratios were 23.52%,42.58%,and 33.90%in three intervals of contour area(<400.00 mm~2,400.00～2500.00 mm~2,and>2500.00 mm~2);conducted tensile and tear mechanical properties tests on farmland plastic films and found that the maximum value of tensile load distribution,tear load distribution,and displacement distribution were 0.70～0.80 N,0～100%,1.0～2.0 N,respectively;determined the average distribution of soil compaction within 150 mm was ranging from 171.05 to 271.70k Pa,and the average distribution of soil moisture content was within 11.78%～25.76%.Second,we measured the mass ratios of soil particle sizes>5.00 mm,2.00～5.00 mm,1.00～2.00 mm,0.50～1.00 mm,0.25～0.50 mm,and<0.25 mm were 21.70%,23.80%,10.80%,16.70%,15.30%,and 11.70%,respectively;employed the Box Behnken test with three factors and three levels to determine the contact parameters of the soil model:dynamic friction coefficient of 0.30,the static friction coefficient of 0.40,and collision coefficient of restitution of 0.20.(2)The design of the complete machine and key operating components for the residual film recycling machine in the seeding layer.This thesis proposed the overall plan and working principle of the seeding layer residual film recycling machine,combined with theoretical analysis and virtual simulation methods determining the structural shape of the arc-shaped teeth of the residual film pickup component,and finally obtained the working parameter range of the key operating components of the machine.The results show that the minimum total power consumption of the machine was 71.00 k W,the speed of the tooth drum device was20.00～138.00 r/min,the minimum depth of soil penetration was 43.75 mm,the rotation speed of the membrane removal device was 628.00～1884.00 r/min,and the height of the membrane collection box from the ground during operation is 260.00 mm.(3)Research the dynamic characteristics of the toothed drum device during the operation process.This study constructed a mathematical model of the key operating component of the tooth binding drum device,the arc tooth insertion stage;clarified its working parameters(machine operation speed,operation depth,insertion angle),structural parameters(arc tooth width,arc tooth length),the influence of soil parameters,and the friction coefficient between soil and arc-shaped teeth on the stress situation of arc-shaped teeth in soil;built the mathematical model of the key operating part of the tooth binding roller device during the film binding stage of the arc tooth binding and determined the influence law of the parameters such as the taper angle of the arc tooth binding,the soil resistance,the traction force of the machine and the elastic modulus of the residual film on the strain energy of the residual film in the extrusion process;identified a mathematical model for the key operating component of the arc-shaped toothed drum device during the film conveying stage,clarifying that the resistance in the soil during the arc-shaped toothed film conveying process is related to the operating speed of the machine,the operating depth,the friction coefficient in the soil,and the friction coefficient between the soil,arc-shaped toothed and residual film,the resistance in the air is related to parameters such as the suspension speed of the residual film,the resistance coefficient of the air flow,and the area of the residual film;defined mathematical model of soil particle throwing resistance was constructed,and the influence of structural parameters(arc tooth width,rotation radius of tooth roller device),working parameters(machine operation speed,rotation angle speed of tooth roller device),soil bulk density,and friction coefficient between soil and arc tooth roller device on soil throwing resistance;finally clarified the reasons for soil blockage in the tooth roller device during operation and obtained the range of values for the operating speed of the machine,the speed of the toothed drum device,and the operating depth based on the discrete element method optimization were 4.00～6.00 km/h,30.00～70.00 r/min,and 80.00～140.00 mm,respectively.(4)For investigating the dynamic characteristics of the key component of the seed layer residual film recycling machine during the operation process of the film removal device,first of all,this thesis constructed the mathematical model of the film removal device within the scraping stage while clarifying the influence of factors such as air resistance coefficient,density,residual film quality,residual film area,and installation position on the initial velocity of the residual film.Then,we also built the mathematical model of the membrane removal device in the pneumatic conveying stage,clarifying the influence of parameters such as residual film suspension velocity,airflow resistance coefficient,residual film area,residual film mass,and initial residual film velocity on the movement speed and force situation of the residual film at any time.Finally,based on theoretical analysis,the operating mechanism of the membrane removal device was explored by combining the flow field simulation of the membrane removal device and the field performance test of the device.(5)A field operation performance test was conducted on the residual film recycling machine for sowing layers.This study conducted a single-factor experimental study using the Taguchi OA experimental design method,illustrating the influence of operating parameters such as depth of machine operation,the forward speed of the machine,and speed of the toothed drum on the residual film pickup rate and wrapping rate;obtained the significance order of each factor on the residual film pickup rate was as follows:operating depth,speed of the toothed drum,and forward speed of the machine,whereas the order of significance on the film wrapping rate is the speed of the toothed drum and the operating depth,respectively.To study their interaction factor effect,this thesis conducted and analyzed a three-factor and three-level Box Behnken central combination experiment on the residual film pickup rate;built the quadratic mathematical regression model about that experiment;finally,obtained the significance order of the influence of each interaction on the residual film pickup rate was(the forward speed of the machine×the speed of the toothed drum)and(the forward speed of the implement×depth of operation)and(speed of the toothed drum×depth of operation).(6)Research on optimizing and verifying the residual film recycling machine for the seeding layer.By setting constraints,the combination with the highest satisfaction was obtained as follows:the forward speed of the machine is 4.84 km/h,the speed of the toothed drum is 49.34 r/min,the operating depth is 100.00 mm,and the predicted residual film pickup rate of the model is 69.20%.Meanwhile,through field validation experiments,the average residual film pickup rate of the machine was 66.84%,and the average film wrapping rate was 1.39%,the relative error between the average value of the residual film pickup rate and the optimized value was 3.41%.That indicated that the constructed mathematical regression model is accurate and reliable.As the designed residual film recycling machine for the sowing layer has feasible operating principles and effects,it can be used for picking up agricultural sowing layer residual film.This study can provide a theoretical basis for the research and development of agricultural and residual film recycling technology equipment. |
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