| Rapeseed is an important oil crop in China.The mid-lower reaches of the Yangtze River is the main production areas of rapeseed in China.The rice oil water dry rotation is the main planting mode in this area.The key difficulties of seed bed preparation are the stubble height,straw amount and water content fluctuation of rice before direct seeding of rapeseed.In view of the practical problems such as shallow plough layer caused by long-term rotary tillage in the rice oil rotation area in the mid-lower reaches of the Yangtze River,and the decline of seed bed quality caused by a large amount of straw returning to the field,this paper systematically analyzed the research progress of technology and equipment in this field at home and abroad,combined with the agronomic requirements of rapeseed planting,aimed at developing high-quality seed bed preparation suitable for mechanized sowing of rapeseed.In this paper,the working mechanism of the plowing-rotating combined seed bed preparation device and its buckle of rapeseed direct seeder were studied.The main research contents were as follows:(1)The research status of seed bed preparation technology at home and abroad was systematically analyzed,and the overall design of rapeseed direct seeder plowing-rotating combined seed bed preparation was carried out.(1)The physical and mechanical parameters of soil and rice stubble in the rice oil rotation area in the mid-lower reaches of the Yangtze River were measured and analyzed.(2)The results showed that the suitable tillage depth of rapeseed bed preparation device was 160 ?200 mm.The rapeseed bed preparation device should achieve a more uniform mixture of rice straw and soil,and had a higher straw coverage rate;It was clear that the preparation of rapeseed direct seedbed in the rice oil rotation area of the mid-lower reaches of the Yangtze River was soil crushing,leveling and furrow opening.The main influencing factor of the quality of rapeseed direct seedbed preparation was the treatment of the previous rice straw.(3)The main structure of rapeseed bed preparation was analyzed and determined.The working process of seedbed preparation was described as the tillage operation of deep tillage and stubble burying first,and then rotary tillage and soil breaking and leveling.The influence of interaction among the plough device,rotary tillage device and furrow opening device on the quality of seedbed preparation was explored.(4)It was put forward that the rotary blade roller adopted the "inverted U" type installation mode in the same rotary plane,and its operation principle was defined as the inner side throwing behind the cutting block syncline and the blade arrangement mode of rotary tillage device.(5)The mechanical model of throwing soil with rotary blade was established,and the lateral migration distance of soil particles from rotary blade was positively correlated with rotary radius of rotary blade and angle between normal section and lateral section;The angle between the front section and the side section was 60°.When the turning radius of the outer blade was 260 mm and the turning radius of the inner blade was 245 mm,the interaction of the rotary tillage device,the furrow opening device and the plough device could form a seed bed suitable for rapeseed mechanical sowing.(2)The working mechanism and device design of buckles made by plowing-rotating combined seed bed.(1)The overall structure design of plough device was carried out,the main structural parameters of plough and double wing plough were determined,and the working process and working principle of double wing plough were defined;The analysis results showed that the machine had good trafficability and applicability when the number of the plough body of the plough group was small,and the symmetrical arrangement could ensure the smooth operation of the machine.The plough device was determined to be composed of two groups of plough arranged symmetrically and the double wing plough installed in the middle position.Combined with the standard requirements,the longitudinal spacing of the plow body should not hinder the overturning requirements of the latter plow body.The analysis results showed that the transverse center installation spacing of the two adjacent plows was 300 mm,the transverse center installation spacing of the adjacent plows and double wing plows was 320 mm,and the width of the plough device was1540 mm.(2)The mechanical model of the bucking stage was established,and the bucking mode of the plough was defined as the bucking mode of the plough.The key analysis was that in order to achieve better bucking in the bucking stage,the bucking mechanism of the plough was determined based on the larger overturning torque when the width depth ratio was 1.5 ? 1.96,there was a negative correlation between the turning torque and the aspect ratio.(3)Based on the bucking mechanism,the plow surface structure and parameters were analyzed.The results showed that the length of plowshare affected the bucking effect,and the length of plowshare should be greater than 89.9mm.The forming principle of plow surface was analyzed,and the mathematical model of the key influencing factors was established;The surface parameter model of double wing plow was established.Combined with the actual operation requirements,the height of guide curve of plow surface was 230 mm,the opening was 180 mm,and the installation angle of plowshare was 25 °,The tangent angle was 110 °,element line angle was 32 °,the was 45 °;Considering the installation size and sliding cutting effect of the cutting edge,the mechanical analysis of the cutting edge showed that the sliding cutting angle was 35°,the normal cutting edge angle was 50°.(4)The analysis results showed that the left and right forces counteract each other,and there was no obvious lateral force;The mechanical model of plow surface operation was established,and the main factor affecting the operation resistance was the width of plowshare,and the operation resistance increased with the increase of the length of plowshare;The mechanical model of soil ridge and plough was constructed,and the process of plough surface bucking was explained.(3)EDEM software was used to simulate and test the preparation process of plowing-rotating combined seed bed.(1)The simulation test results of soil straw distribution under different forward speeds showed that the cross section of the box surface was V-shaped symmetrical distribution,and the angle between the V-shaped edge and the horizontal plane increased with the increase of forward speed;The results showed that with the increase of forward speed,the soil particles on the outside of the compartment increased significantly.Under the three forward speeds,the distribution ratios of soil particles on the left side of the compartment,the middle side of the compartment and the right side of the compartment were 1:0.92:1.05,1:0.89:1.05 and 1:0.88:1.07,respectively;The results showed that with the increase of forward speed,the straw on the outside of the compartment increased significantly.Under the three forward speeds,the distribution ratio of soil particles on the left side of the compartment,the middle side of the compartment and the right side of the compartment were 1:0.52:1.25,1:0.7:1.44 and 1:0.59:1.04,respectively.(2)The simulation test results of soil straw transport law after seed bed preparation showed that the surface quality could meet the agronomic requirements of rapeseed planting;The analysis of soil transport law showed that soil particles were exchanged up and down along the vertical direction under the interaction of plough device and rotary tillage device,which realized the downward movement of surface soil particles and the upward movement of middle and bottom soil particles,and achieved better seed bed preparation quality;The analysis of straw migration law showed that straw moved downward along the vertical direction to meet the requirements of straw burying operation.(3)The results of single factor simulation showed that the optimal forward speed was 2.1 ? 3.5km/h,the tillage depth was 160 ? 200 mm,and the rotary tillage speed was 180 ? 250 r / min,which could meet the requirements of rapeseed sowing surface flatness and straw coverage rate.(4)The simulation test results of the effects of different seed bed preparation devices on seed bed quality showed that after the seed bed preparation devices of rapeseed no tillage direct seeder,rotary rapeseed direct seeder and plowing-rotating combined rapeseed direct seeder were operated,the car surface flatness were 32.11 mm,24.32 mm and 18.48 mm respectively.The distribution ratio of straw in the surface layer(0 ? 5cm),middle layer(5 ? 10cm)and bottom layer(> 10cm)of the seed bed was 1:0.13:0 after the operation of the seed bed preparation device of no tillage rapeseed direct seeder with rear furrow.The distribution ratio of straw in the surface layer,middle layer and bottom layer of the seed bed was 1:0.30:0.33 after the operation of the seed bed preparation device of rotary tillage rapeseed direct seeder.However,the ratio of straw distribution in the surface,middle and bottom layer of the seed bed was 1:1.24:0.40 after the operation of the plowing-rotating combined seed bed preparation device.The straw cover and seed bed thickness of the plowing-rotating combined seed bed preparation device were better than those of the no tillage direct seeder and the seed bed preparation device with only rotary tillage.(4)The field experiment on preparation of plowing-rotating combined seed bed of rapeseed direct seeder and comparative analysis of its performance.(1)The results of field experiment and comparative analysis of different preparation methods showed that the length of plowshare had a significant effect on operation resistance;The tillage depth had a significant effect on the bucking rate and the resistance.With the increase of tillage depth,the operation resistance increased significantly,and the straw coverage rate increased significantly;The results showed that the length of plowshare was 150 mm,the working depth was 180 mm,the working resistance was 5.54 k N,and the bucking rate was 91.25%.(2)The results showed that the seedbed could be turned first and then rotated,and the stability of the depth into soil was higher than90.58%;The results showed that the flatness of the chamber surface was 14.27 ?20.06 mm,the straw coverage rate was 84.65% ? 93.24%,and the soil crushing rate was higher than 91.26% under different soil depths.The chamber surface quality met the requirements of rapeseed sowing.(3)The results of field orthogonal experiment on the preparation of rapeseed direct seeder plowing-rotating combined seedbed showed that the depth of soil had a significant effect on the operation power and the straw coverage rate;Forward speed had a significant effect on power,straw cover rate and soil crushing rate;Rotary speed had a significant effect on the rate of broken soil;The results showed that the depth of soil was 180 mm,the forward speed of the whole machine was 2.1km/h,the rotary speed was 250 r / min,the power was 27.43 kw,the thickness of plough layer was 231 mm,the straw coverage rate was 90.88%,the soil crushing rate was 93.2%,and the flatness of chamber surface was 21.15 mm.(4)The results showed that under two different conditions of rice straw,the seed bed preparation quality of the two methods met the requirements of rapeseed sowing;The average tillage depth of the combined plough and rotary seedbed was 249 mm and231 mm respectively,which was 137 mm and 110 mm higher than that of the rotary seedbed;Compared with the rotary tillage seed bed,the straw mulching rates were increased by 33.94% and 28.36%,respectively,which was better than the rotary tillage seed bed;(5)The field experiment results showed that: after the seed bed was prepared,the evenness of the chamber surface and the straw coverage and distribution were the best,the broken soil rate met the agronomic requirements of rapeseed planting,the seed bed thickness was 241 mm,and the seed bed quality was significantly better than that of no tillage direct seeder and rotary tillage direct seeder.The results showed that the seedling emergence rate of plowing-rotating combined rapeseed direct seeder was the best,and the plant height,biomass and main root system length of seedling stage,full flowering stage and harvest stage were better than those of no tillage direct seeder and rotary rapeseed direct seeder.The preparation of plough rotation seedbed is helpful for stable and high yield of crops. |
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