| The Huang-Huai-Hai summer corn region is the largest corn concentrated production area in China,and is also the main double cropping area of wheat corn rotation.At present,the straw returning method has many problems,such as large wheat straw coverage,more stubble,uneven cutting stubble,and poor straw crushing effect,which brings many problems to corn sowing.The existing small and medium-sized corn planters mostly use spade type and disc type trenchers.During high-speed seeding operation,excessive wheat straw will lead to the blockage of the trencher,resulting in missed sowing,missed planting,and later seedling size issues.In addition,the wheat straw,wheat bran and weeds covered on the corn planting belt will increase the disease and insect pests of corn,so it is necessary to clean up the corn rows far away from the plant.In view of the above problems,this paper had carried out the research on the anti blocking device of the corn no tillage planter.The main research contents and conclusions are as follows(1)The wheat-corn planting pattern in Huang-Huai-Hai region was investigated,and the influence of planting specifications on mechanized operation was analyzed.According to the mechanical and physical properties of wheat plants and soil,the calibration tests of intrinsic parameters,mechanical parameters and contact parameters were completed by combining physical repose angle with EDEM simulation.Through the conventional soil bin test,the influence of different openers on the amount of straw,the forward speed of the machine and the depth of the soil under the no-slip model on each index was determined.According to the optimal parameter combination obtained by discrete element calibration,the influence of straw,stubble and soil on the opener under the bonding model was analyzed,and the aggregation law of straw under high-speed motion and the blocking mechanism of opener were obtained.(2)According to the blocking mechanism of the opener,the method of oblique cutting and shallow rotary stubble cleaning was defined to achieve anti-blocking effect.According to the existing agronomic requirements of corn planting,the overall structure of the anti-blocking device for oblique shallow rotary stubble cleaning was designed,and the operating parameters of the machine were defined.The structure increased the stubble area(cutting width)and stubble angle,and improved the side throwing amount of straw and soil.Through theoretical analysis,the structural parameters of the inclined shallow rotary anti-blocking device were designed,and the range and relationship of each parameter were determined.According to the device structure,the stress analysis of the process of the plow blade moving into the soil and removing the stubble from the soil was carried out,and the factors affecting the working performance were determined.(3)An oblique tilling blade was designed and optimized to address the problems of large soil movement and high power consumption in traditional rotary tilling blades.Before the design,the relationship between wheat straw and shear angle and tool edge angle was analyzed.With the increase of shear inclination angle,the shear force decreases,and with the increase of tool edge angle,the shear force increases as a whole.Choosing the appropriate blade could effectively reduce the cutting resistance and power consumption,achieving the cutting effect on the straw.On the basis of comparing the force of the oblique blade at different points,the value of the blade angleθwas guaranteed,and the side cutting edge curve preferentially selects the Archimedes spiral as the edge curve with the smallest power consumption and torque.In order to ensure that more soil and straw slip from the side of the blade,the end face of the blade’s tangent section was designed according to the structure of the backward rounded grass wheel.The structural parameters of the blade were as follows:the initial radius was 66 mm,the initial sliding angle was 30°,the end radius of the side cutting edge was 210 mm,and the end sliding angle was 50°.(4)The discrete element method was used to simulate the operation process of the anti-blocking device in the field,and the multi factor and single factor experiments were carried out with straw clearance rate,soil disturbance coefficient and power consumption as evaluation indexes.When the oblique angle was 0°,the multi factor discrete element simulation test results showed that the influence of the index from large to small was the blade rotation speed,the forward speed and the cutter blade spacing.Through regression analysis and significance test,the influence of rotation speed,speed and oblique angle on the three evaluation indexes and the primary and secondary order were determined.The oblique angle had the greatest influence on each index.The regression model was optimized by multi objective function to obtain the optimal parameter combination,rotation speed 400 r/min,forward speed 6km/h,oblique angle 18.5°,straw clearance rate74.5%,soil disturbance coefficient 34.7%,power consumption 1.36k W.The single factor test was carried out on the structural parameters of the blade,and the effects of the bending angle and the optimized blade curve model on the straw clearance rate,soil disturbance coefficient and power consumption under the same conditions were compared and analyzed.The simulation test showed that the greater the bending angle,the greater the impact on the straw and soil in the tillage layer,and the optimal bending angle was 150°.(5)In order to determine the influence of the structural parameters of the device on the actual operation,an indoor soil bin test was conducted.Firstly,the structure of the soil trough bench was designed to realize the functions of oblique angle adjustment,constant speed and blade replacement.The torque sensor was combined with the six-component force sensor to realize the determination of power consumption.In the soil bin test,the oblique angle of 0°was used as the control group and compared with the oblique angles of15°,22.5°and 30°.The single factor test showed that when the oblique angle was 0°,under the same operating conditions,when the rotation speed of the blade reaches more than 400r/min,it could meet the operating requirements and the outer structure of the blade was better than the inner structure of the blade in terms of straw cleaning and force.The comparative test results showed that increasing the oblique angle and rotation speed could effectively reduce the straw residue on the seedbed and realize the cleaning of the seedling belt.The rotation speed and oblique angle had a great influence on the seedbed parameters.Reducing the oblique angle and rotation speed can effectively improve the seedbed quality parameters.When the rotational speed was constant,the horizontal resistance increases with the increase of the oblique angle,and the vertical resistance and lateral resistance change more complicated.When the rotational speed was 500r/min,the oblique angle had little effect on the overall power consumption.The results of oblique angle optimization test showed that the straw clearance rate increased by 14.7%,the soil disturbance coefficient,soil breaking rate and soil backfilling rate increased by 72.1%,33.2%and5.0%respectively,and the power consumption increased by 4.7%.(6)The field test results of the anti blocking device of the corn no-tillage planter showed that when the straw coverage was 1.02 kg/m~2and the forward speed was 8 km/h,the straw clearance rate was 91.85%,the stability of the ditch depth was 86.67%,and the soil moving rate was 26.47%.The results showed that the anti blocking device could effectively reduce the soil disturbance and ensure the stability of the fertilization and sowing depth during high-speed operation.The field test of sowing was conducted by optimizing the improved device,The sowing requirements shall meet the national standards,and can meet the requirements of high-speed operation of corn no tillage planter in the wheat straw mulched land in the Huang-Huai-Hai region. |
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