| Rapeseed is widely planted in the middle and lower reaches of the Yangtze River.In this area,the groundwater level is high,the rain and heat in the sowing season are at the same time,and the rainfall is more.The seedbed leaching is the key factor affecting the yield of rapeseed.The rapeseed direct seeding machine widely used in current production practice has problems such as uneven bed surface,unstable furrow type and difficult control of sowing depth after operation.Combined with the requirements of traditional rapeseed planting seed bed preparation,this paper proposes a convex ridge surface construction agronomy with high middle and low sides of the box surface,and develops a set of box surface finishing device with closed furrow opening,active spinning convex ridge and profiling furrow opening.Discrete element simulation analysis and field verification test were carried out,and the evolution of furrow and box surface after operation was tracked and analyzed.The main research contents are as follows:(1)Combined with the agronomy of rapeseed planting,the traditional seedbed preparation requirements were analyzed,and on the basis of traditional agronomic requirements,a convex ridge seedbed structure was further proposed.The overall structure of the convex ridge box surface construction device and the composition of functional components such as rotary tillage stubble components,furrow opening components,side transmission system,box surface shaping components,profiling components were clarified.The working principle is described and the technical parameters of the device are formulated.(2)The key working parts of the convex ridge surface construction device were designed and analyzed.The structural design of closed ditching components was carried out.The design of plough body is based on the horizontal straight line method.The height of plough guide curve before furrow opening is 350 mm,the opening is 120 mm,the endpoint tangent clamp is 85°,the soil lifting angle of plough blade is 20°,and the variation law of element line angle decreases from 42 ° to 41°,and then increases from 41°to 48°.After ditching,the height of plough guide curve is 520 mm,the opening is 210 mm,the angle of endpoint tangent is 65°,the soil lifting angle of plough blade is 5°,and the variation law of element line angle decreases from 35 ° to 32°,and then increases from 32°to 47 °.Based on the change law of soil migration and volume before and after the operation of the device,the structure design of the shaping roller is carried out.The shaping roller is composed of the middle straight section,the cone section and the bell mouth section.The angle between the cone section bus and the middle straight section is 3°,and the angle between the bell mouth section bus and the horizontal plane is 61°.The force analysis of the shaping roller is carried out,and its balance equation is listed.The motion of the shaping roller is analyzed,and the minimum speed range of the shaping roller is 127-175 r/min.The transmission system of the floating shaping roller is determined.The force calculation of the profiling mechanism was carried out.The material of the spring was oil quenched and tempered silicon-manganese spring.The free height of the spring was 264.80 mm,the height when it was compressed was 97.50 mm,the total number of turns was 20,the wire diameter was 5.00 mm,the pitch was 14.29 mm,the spiral angle was 6.49°,and the unfolding length was 2529.48 mm.(3)The simulation model was established by using the discrete element simulation software EDEM,and the three-factor and three-level Box-Behnken test was carried out.The forward speed of the convex ridge chamber surface construction device,the rotation speed of the rotary blade roller and the rotation speed of the shaping roller were used as the test factors.The inclination angle of the ditch wall and the inclination angle of the arc chamber surface were used as the response indexes.The response surface analysis of the ditching quality and the chamber surface finishing quality of the device was carried out,and the quadratic polynomial regression model of each response index was obtained.The optimal operating parameters of the device are forward speed of 3.8 km/h,rotary blade speed of 276 r/min and shaping roller speed of 146 r/min.The soil mixing ability of the device was analyzed.The soil after the operation was vertically downward from the horizontal height of the top of the box surface to a depth of 50 mm,and a total of 3 layers were taken.The analysis showed that 54.88%of the particles in the upper layer were mixed into the depth range of 50-150 mm after the operation of the device.The distribution of the original middle layer particles in the upper,middle and lower layers accounted for 28.91%,35.29%and 35.80%respectively,indicating that the device had the strongest mixing ability for the middle layer particles.The function of the shaping roller is verified by EDEM,and the shaping roller can effectively achieve the expected shaping goal.The finite element analysis software was used to analyze the trenching components.The maximum stress value appeared at the bolt hole at the bottom of the front end of the side retaining plate,which was about 221.42 MPa,which was less than the yield limit of the material.The maximum deformation appeared at the plow tip before the trenching,which was about 2.87 mm.The structural strength of the trenching components met the requirements of the stable operation of the device.(4)Field experiment of convex ridge construction device.Field experiments were carried out under the conditions of average soil moisture content of 9.61%～37.21%,average soil firmness of 1403.90～5130.14 kPa,and average stubble height of 0～43.31 cm.The results showed that the average width of upper furrow fluctuated in the range of 31.47～43.22 cm,the average depth of furrow fluctuated in the range of 14.70～20.32 cm,the stability coefficient of upper furrow width fluctuated in the range of 92.16%～97.01%,and the stability coefficient of furrow depth fluctuated in the range of 93.39%～95.26%.The flatness of the box surface fluctuates in the range of 7.93～12.31 mm.Compared with the operation quality of the tillage device of the rape direct seeding machine,the results showed that the flatness of the box surface increased by 42.40%,the stability of the furrow width increased by 41.69%,and the width of the furrow decreased by 20.31%under the premise of realizing the same furrow depth.In order to test the construction effect of convex ridge compartment,irrigation test was carried out.During the irrigation process,the water level gradually increased from the bottom of the furrow to the edge of the compartment,and then gradually spread from both sides of the compartment to the center of the compartment.The evolution process of the furrow type of the drainage furrow was tracked and analyzed.The analysis showed that the average furrow depth gradually decreased from the initial 18.53 cm to 12.66 cm,the average furrow depth decreased by 31.68%,the average upper furrow width gradually increased from 37.18 cm to 45.23 cm,the average upper furrow width increased by 21.65%,and the anti-waterlogging effect of the convex ridge surface reached the predetermined target.During the whole tracking period,the furrow type showed a slow leveling law,and there was no field drainage phenomenon caused by the collapse of the ditch wall. |
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