| The research was supported by the special fund project for the Modern Agricultural Industry Technology System(Project No.GARS-04)and the National Key R&D Plan Project(Project No.2018YFD0201004).Aiming at the problems of low effective accumulated temperature,increased pest and disease rate and low utilization rate of straw stubble resources caused by the full coverage of straw stubble under the mode of no tillage and straw mulching.This paper has carried out the following research.Based on the 2BMFJ series of no till planter,this paper studies the technology of straw stubble recycling and mixing ratio.Aiming to improve the soil environment and reduce the use of chemical fertilizer and pesticide.Based on the study of the working principle and characteristics of the straws cleaning device,and the mechanical energy of straws scattering.This paper puts forward a technical method and supporting device of the ratio of straws returning to the field.The key technologies are theoretical analysis,digital virtual prototype design and modeling,computer simulation analysis,high-speed camera technology and experimental research.The main research contents and results are as follows:(1)Construction of the experiment platform of the ratio adjustment technology of the side stubble recovery of the no tillage precision straw mulching machine in the original stubble field of corn.This paper compares the operation mode and principle of the rigid-tooth and spring-tooth type straw cleaning device of 2BMFJ series no till planter.Puts forward a platform construction scheme,analyzes and designs the key structure and parts of the straw cleaning device through theoretical analysis and digital modeling technology,and probes into the time when the straw cleaning device of 2BMFJ series no till planter throws straw residue laterally by combining three factors and three levels orthogonal test method.The experimental results show that the primary and secondary order of the influence of each factor on the rate of stubble removal is rotation speed,operation speed,and the angle of tooth deviation of the stubble removal,in which the rotation speed and operation speed have a significant effect on the rate of stubble removal,but the angle of tooth deviation of the stubble removal is not significant.The factors have an effect on the rate of stubble removal The order is the declination angle,rotation speed and operation speed of the cleaning straw,and the declination angle and rotation speed of the cleaning straw have a significant effect on the width of the covered straw,while the operation speed has no significant effect.(2)Dynamic characteristics of stubble based on high-speed camera technology.First,collect and sort out the corn stubble in the standard ridge of northeast in China,and measure its basic physical parameters.On this basis,the movement process of the stubble on the stubble cleaning tine and the lateral throwing process after the stubble is separated from the stubble cleaning tine are studied in depth,and the corresponding dynamic model of the stubble is established.From the model,we can see that when the stubble cleaning tine is thrown laterally.When the stubble is scattered,the stubble near the end of the toothed rod slides outward,and finally throws out along the tangent direction of the tine.The stubble near the inner side keeps relatively static with the tine.The dividing point is related to the deflection angle,rotation speed of the tine and the dynamic friction between the tine and the stubble.At the moment of separation,the stubble is affected by the centrifugal force generated by the rotation of the spring-tooth around the axis and the internal air flow of the stubble cleaning device.The process of stubble throwing in the air is modeled and analyzed.Combined with the high-speed camera technology and the three factors and five levels quadratic regression center combination test method,the process of lateral throwing of stubble is dynamic Modify the mechanical model.Finally,the modified model is used to draw the trajectory of stubble movement with MATLAB,and the spatial distribution of stubble is visualized and analyzed.According to the distribution of stubble,it can be seen that when the height of stubble throwing increases with the increase of rotation speed of spring-tooth around the shaft.And too large angle of spring-tooth is easy to cause the stubble not easy to be separated from the teeth and brought back to the seed bed.To reduce the quality of straw cleaning.According to the cloud chart of the spatial distribution density of the stubble,it can be seen that most of the stubble is in the lower side at the beginning of the scattering process.With the process of the scattering,the vertical height of the stubble increases gradually,and the spatial vertical distribution difference is also significant.(3)Research and design of the ratio adjustment device for straw stubble recycling.Based on the characteristics and distribution of straw stubble,this paper presents a technical method and supporting device of straw stubble recycling and proportioning.By using the mechanical energy of straw stubble side dumping and proportioning,part of straw stubble can be recycled to the recycling box.A kind of control baffle of straw stubble recycling and proportioning in the same step is designed to adjust the ratio of straw stubble splitting by changing the area of recycling port.The structure of each part of the device is deeply analyzed with modular design.Based on the study of the spatial distribution cloud chart of straw stubble,the proportion of straw stubble mulching and returning to the field under the combination of different parameters of the scattering control baffle angle and the recycling port area is explored.When the ratio of straw stubble recycling is no less than 50%,the angle of the scattering control baffle is 45°and the existing straw cleaning device is not reduced.On the basis of industrial quality,a multi link angle control mechanism is designed,and the influence rule of each component parameter of the structure on the tooth deflection angle of the straw cleaning bullet is explored through theoretical modeling and software dynamic simulation analysis.Based on the principle of the brachistochrone,the curvature of the guide plate on the dispersion control baffle is analyzed,and the brachistochrone model considering friction resistance is constructed,on which the guide plate is designed.The preliminary design of the ratio adjustment device for straw stubble recycling was completed.(4)Based on the computer simulation,the influence analysis of the performance parameters of the straw stubble recycling ratio adjustment device.Through the computer simulation technology,this paper analyzes the flow field characteristics,the mechanical characteristics of the spring-tooth and the scattering characteristics of the stubble in the straw cleaning device.Firstly,the CFD numerical calculation model of the straw cleaning device is established,and the flow field pressure and air flow characteristics are studied.The results show that,in terms of air pressure distribution,with the movement of the straw cleaning tines,there is a low pressure area at the bottom of the rotating shaft of the straw cleaning tines and at the recovery port of the scattering control baffle,and a high pressure area at the lower side of the scattering control baffle and in front of the straw cleaning device.In terms of air flow,one part of the air flows around the shaft with the straw cleaning tines,and the other part flows out through the recovery port of the scattering control baffle.The rest of the air flows around the surface under the influence of the control baffle.On this basis,the influence of three factors on the pressure and air flow characteristics of the internal flow field of the straw cleaning device is explored.The results show that the air flow velocity at the recovery port of the dispersion control damper has great difference in different positions,which is mainly affected by the rotation speed and operation speed of the cleaning straw bullet teeth.Through the discrete element simulation analysis,the process of cutting soil with straw cleaning tine is studied.The results show that with the movement of straw cleaning tine,the soil resistance increases first,then stabilizes and finally decreases.The depth of soil,the working speed of machine tools and the working speed of spring-tooth are selected as the experimental factors.The influence law of each experimental factor on cutting load is explored by orthogonal test method.The results show that the primary and secondary order of the influence of each factor on the mean value of soil load is:the depth of soil,the speed of cutting,the speed of cutting.At last,the simulation analysis of the process of scattering the stubble in the straw cleaning device is carried out by the discrete element simulation software.When the position of the control damper is not changed,the coverage width of the stubble to the seed bed is adjusted by the angle of the end of the control damper.The simulation results show that there is a positive correlation between the spreading width of stubble and the end break angle.When the design object is two rows of straw cleaning device with ridge distance of 65 cm,the end break angle is 150°.(5)Field test and environmental factors analysis of the ratio adjustment device for straw stubble recycling.Through the field experiment to explore the relevant parameters of the proportion of stubble mulching and returning to the field,using four factors and five levels of quadratic regression orthogonal central combination experiment method,the optimal parameter combination corresponding to different stubble returning to the field was obtained.The experimental results show that,based on the mechanized planting mode of no tillage and no straw mulching,the ratio adjustment device of straw stubble returning to the field can realize the parameter adjustment of straw stubble returning to the field.In order to verify the accuracy of the model,taking 50%and 70%of the ideal stubble mulching and returning ratio as examples,the corresponding structure and operation parameters of the device were explored.When the combination of the parameters was 21°of the angle of deflection of the teeth,1120 cm~2 of the recycling port area,5 km/h of the operation speed,1.1 kg/m~2 of the stubble mulching amount,the proportion of stubble mulching was 52.3%.When the combination of the parameters was 21°angle of the spring-tooth,890 cm~2 area of the recycling port,8 km/h operation speed,1.1 kg/m~2 of stubble mulching,the proportion of stubble mulching was 71.9%.Based on the analysis of the influence of environmental factors on the optimized ratio adjustment device of straw stubble returning to the field.Taking the environmental natural wind as a single factor variable to explore its influence on the operation quality.The test results show that different environmental wind speed and wind direction have significant influence on the ratio error of straw stubble returning to the field.Among which,for the environmental wind speed,when the ratio adjustment device of straw stubble returning to the field is from south to north.During operation,the wind speed shall not exceed 7.2 m/s,the proportion error of straw stubble mulching and returning to the field increases with the natural wind speed of the environment,while from north to south,it mainly decreases first and then increases.For the environmental wind direction,when the straw stubble returning to the field recycling ratio device works from south to north,the proportion error of straw stubble mulching and returning to the field decreases first and then increases with the natural wind direction of the environment trend.While from north to south,the main trend is to increase first and then decrease. |
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