| Rapeseed and wheat are important oil-bearing crops and food crops in China.The sowing time of rapeseed and wheat is adjacent and the mechanized operation process is similar,which is an urgent need to develop the planter for rapeseed and wheat to improve the utilization rate of the agricultural machinery.With the rapid development of modern agricultural new business entities,the development of large and medium-sized combination planter to improve the efficiency has become the development direction of promoting the mechanized sowing level of rapeseed and wheat.Aiming at the problems that the existing no till planters are difficult for rapeseed and wheat to achieve high-speed sowing and synchronous fertilization due to wide range of sowing quantity adjustment and obvious seed size difference,meanwhile,the adaptability of metering device and ditching device to wide operation under land slope is poor,a broad width and high speed air-assisted planter for rapeseed and wheat was developed.The research in more detail including:(1)The research status of rapeseed and wheat sowing technology at home and abroad was systematically analyzed.According to the requirements of high-efficiency sowing operation of broad width and high speed air-assisted planter for rapeseed and wheat,the overall design scheme of broad width and high speed air-assisted planter for rapeseed and wheat was put forward based on foldable frame,air-assisted seeding and fertilizing,and profiling chisel sowing ditch.The working process and principle of the prototype were described The structure and its parameters of the air-assisted seeding system,the air-assisted fertilizer system,and the profiling chisel sowing ditch device were determined.In order to realize broad width and high-speed sowing operation and meet the planting agronomic requirements of rapeseed and wheat,the operation width of the planter was 4.8 m,the operation speed was in the range of 6 to 12 km/h,the operation efficiency ranged from 2.88 to 5.76 hm~2/h,the profiling chisel sowing ditch device was dislocation arrangement,the number of sowing lines was 24,and the number of fertilizing lines was 12.(2)The structural design and parameter analysis of the key components of the broad width and high speed air-assisted planter for rapeseed and wheat were carried out.a)In view of the fact that the land has a certain slope,which is difficult to match the broad width and high-speed sowing operation,and there is a lack of reliable seeding air-assisted centralized metering device for rapeseed and wheat,a conveying component based on the Venturi principle,a dome shaped distributor device for 24 rows seeding,and a even seeding turbine driven by conveying airflow were developed.When the structure of conveying component and distributor device was fixed,the greater the flow ratio between seed and conveying airflow was,the greater the total pressure loss was,indicating that the greater the quantity of seed conveying was,the higher the requirements for airflow pressure and conveying airflow speed generated by the fan belonging to air-assisted seeding system were.The results showed that when the inner diameter of the conveying seed tube was 81 mm,the length of the accelerating section of the feeding tube was greater than 715 mm,the sphere radius of dome shaped upper arc plate ranged from133.5 to 1 000mm,and the number of even seeding turbine impeller ranged from 4 to10,the seeding for rapeseed and wheat could be realized and the uniformity of seeding mass of each row could be improved.b)The flat top type,the inverted cone installed on the flat top type,the dome type,and the inverted cone installed on the dome type distributor device of the air-assisted fertilizer apparatus were designed and analyzed for realizing the synchronous fertilization as the broad width and high speed air-assisted planter for rapeseed and wheat sowing.Based on Hertz theory,the elastic collision model between pelletized fertilizer and distributor device main part was established.The analysis results showed that the larger the curvature radius of the upper covering plate and the inverted cone of the distributor device,the smaller the speed of the fertilizer particles and the upper covering plate close to each other when the fertilizer particles collided with the distributor device,the easier the fertilizer particles were damaged.Meanwhile,when the diameter of the upper covering plate was 130 mm,the cone angle was 80°,and the height of inverted cone was50 mm,12 rows of fertilizer could be discharged.c)The profiling chisel sowing ditch device based on elastic deformation of profiling roller was developed in order to improve the consistency and stability of sowing depth of each row in uneven land and broad width sowing operation.The interactive profiling mechanical model between soil and chisel sowing ditch device was constructed.The analysis showed that increasing the diameter of the profiling roller and the distance between the profiling wall and the axis could reduce the tendency of the chisel sowing ditch device to rotate anticlockwise in the range of 0°to 45°and ensure the embedded depth.The results indicated that the function of profiling sowing ditch could be realized when the blade edge width ranged from 10 to 14 mm,the profiling roller diameter ranged from 22 to 26 mm,the entrance angle ranged from 15°to 31°,and the sowing depth ranged from 10 to 50 mm.(3)Based on the DEM-CFD gas solid coupling simulation,the performance simulation experiment of the air-assisted seeding system and fertilizer system,and the analysis of seed and fertilizer migration trajectory were carried out.The effects of the structure of the air-assisted seeding system and the air-assisted fertilizer system on the seeding and fertilizing performance were revealed.a)Based on DEM-CFD gas solid coupling simulation,the effects of structural type of conveying components on conveying performance and seed migration trajectory were analyzed and compared.The simulation results showed that the combination of Venturi conveying seed chamber with accelerating conveying tube section and the conveying seed tube with elbow joint had better conveying performance,the backflow rate of rapeseed was 3.01%,however there was no counterflow of rapeseed,and backflow and counterflow of wheat seed.Based on the DEM-CFD gas solid coupling simulation,the parameters of the distributor device of the air-assisted centralized metering device were optimized through the quadratic rotation orthogonal combination test.The sphere radius of dome shaped upper arc plate had the most significant effect on the uniformity of seeding mass of each row.The optimization analysis determined that when the sphere radius of dome shaped upper arc plate was 245 mm,the length of diversion baffle was 20mm,and the height of guiding seed outlet was 20.5 mm,the uniformity variation coefficient of seeding mass of each row of rapeseed and wheat was 4.96%and 3.82%,respectively.The secondary mixing of seeds and conveying airflow could be realized effectively in the dome shaped distributor device.Meantime,DEM-CFD gas solid coupling simulation was used to explore the influence of the distributor device structure of the air-assisted fertilizer apparatus on the fertilizing performance.The results showed that the average values of maximum velocity,the maximum collision normal force,and the uniformity variation coefficient of each row fertilizing quantity of fertilizer particles in the distributor devices of the dome type,the flat top type,the inverted cone installed on the flat top type,and the inverted cone installed on the dome type all increased gradually.The dome type distributor device had the best performance among different structural type distributor device.b)The effects of three kinds of even seeding turbine on the distribution of conveying airflow and the rotating speed of even seeding turbine were compared and analyzed by using the 6-DOF dynamic mesh model in CFD simulation.The simulation results showed that the even seeding turbine with acute inlet and outlet working angles could improve the transportation and mixing of seeds.The rotating speeds of even seeding turbine were 142,135,and 124 r/min respectively,when the inlet working angles of even seeding turbine were acute angle,right angle,and obtuse angle,respectively,and the outlet working angles were all acute angle.The 6-DOF dynamic mesh model in CFD simulation was used to compare and analyze the airflow field distribution in the distributor device with both inlet and outlet working angles being the acute angle,and even seeding turbine with4,6,8 and 10 impellers,respectively.The simulation results indicated that with the increase of the number of impeller,the stability and uniformity of the airflow distribution at the outlet of the even seeding turbine could be improved,and it was conducive to the stable transportation of seeds after mixing.The upper limits of conveying airflow pressure in the distributor device with 4,6,8 and 10 impellers were 1 448,1 508,1 557,and 1 620Pa,respectively.(4)The EDEM simulation and DEM-CFD gas-solid coupling simulation were used to explore the effects of land slope on feeding performance,discharging performance and seed migration trajectory.a)The influence of land slope change on the seeding process of the broad width and high speed air-assisted planter for rapeseed and wheat was analyzed.The seeding random process model of the air-assisted seeding system was established.Theoretical analysis showed that the total seed feeding rate increased with the increase of the tilt angle in the range of-5°to 5°when the tilt direction was the same as the rotating speed of the feeding device.The uniformity variation coefficient of seeding mass of each row of the air-assisted centralized metering device first gradually decreased and then gradually increased with the increase of the random tilt and swing in the range of-5°to 5°along the working direction of the planter.b)Based on EDEM simulation,the effects of random tilt on feeding performance and seed migration trajectory were explored.The simulation results showed that the seeds had a tendency to migrate to the tilt direction when the random tilt was applied.Under the premise of increasing the rotating speed of the feeding device,the influence of the random tilt on the total seed feeding rate could be reduced.The change rate of total seed feeding rate gradually increased with increase of the absolute value of front and back tilt angle in the range of 0°to 5°and the change rate could be up to 50 percentages.At the same time,based on DEM-CFD gas-solid coupling simulation,the effects of random tilt along the working direction of the planter on discharging performance and seed migration trajectory were explored.The results of simulation experiment indicated that the seeds generally migrated to the tilt side of the guiding outlet,and the uniformity variation coefficient of seeding mass of each row of rapeseed and wheat gradually increased with the increase of tilt angle in the range of 4.99%to 14.57%and 3.84%to 19.32%,respectively.(5)Based on intelligent test platform for planting machines,bench test analysis and improvement of the air-assisted seeding system,the air-assisted fertilizer system,and the profiling chisel sowing ditch device of the broad width and high speed air-assisted planter for rapeseed and wheat were carried out.a)Based on adaptability analysis of high speed seeding,verification test of conveying component and distributor device of air-assisted centralized metering device was carried out.The test results showed that when the rotating speed of the seed feeding device ranged from 20 to 50 r/min,the backflow rate of rapeseed was less than 3.2%,however there was no counterflow of rapeseed,and backflow and counterflow of wheat seed.The uniformity variation coefficient of seeding mass of each row of rapeseed and wheat was less than 5%and 3.9%,respectively.The stability variation coefficient of total seeding quality of rapeseed and wheat was less than 1.15%and 1.35%,respectively,and the damaged rate was both less than 0.05%,which could meet the requirements of broad width and high-speed sowing with the working speed in the range of 6 to 12 km/h.b)The fertilizing performance of different structural type of the air-assisted fertilizer apparatus was compared and analyzed,and the verification test was carried out.The test results showed that it was reasonable and reliable to characterize the damaged rate of granular fertilizer by the maximum velocity of fertilizer particles and the maximum collision normal force between fertilizer particles and the distributor device.The fertilizing performance of the dome type distributor device was better than that of the flat top type,the inverted cone installed on the flat top type,and the inverted cone installed on the dome type distributor devices.The analysis showed that the uniformity variation coefficient of each row fertilizing quantity of fertilizer particles in dome type distributor device was in the range of 6.35%to 7.52%,the stability variation coefficient of total fertilizing quantity was in the range of 1.53%to 1.92%,and the damage rate was in the range of 2.97%to 3.26%,respectively.c)The ditching performance of the profiling chisel sowing ditch device based on high speed digital soil slot platform was optimized and analyzed.The test results showed that the profiling roller diameter had the most significant effect on the stability of ditching.When the blade edge width was 12 mm,the profiling roller diameter was 24 mm,and the entrance angle was 22°,the stability coefficient of ditching depth was higher than 94%through the optimization analysis,the stability of ditching was better.d)The effects of structural type and impeller quantity of even seeding turbine on seeding performance of distributor device affected by land slope were focused on analysis and validation.The test results showed that the uniformity variation coefficient of seeding mass of each row with the even seeding turbine was significantly lower than that without the even seeding turbine.When the reciprocating swing combination of front and back,and lateral was 10°relative to the flat land,the uniformity variation coefficient of seeding mass of each row of rapeseed and wheat with 8 impellers was in the range of 4.99%to5.42%and 3.98%to 4.91%,respectively.(6)The influence of land slope on the feeding performance and discharging performance of the broad width and high speed air-assisted planter for rapeseed and wheat was analyzed and determined,and the simulation test was carried out.The test results showed that the total seed feeding rate was mainly affected by the front and back tilt and swing along the planter.The total seed feeding rate gradually increased with the increase of reciprocating swing angle from 0°to 10°and reached 16.31 percentages higher than that without tilt.Meantime,the uniformity variation coefficient of seeding mass of each row of rapeseed and wheat gradually increased from 6.74%to 11.94%and6.71%to 15.89%,respectively,with the increase of absolute value of unidirectional swing angle in the range of 0°to 5°.The uniformity variation coefficient of seeding mass of each row of rapeseed and wheat gradually increased in the range of 4.86%to 10.48%and3.85%to 14.77%,respectively,with the increase of reciprocating swing angle from 0°to10°.(7)Field test and analysis of the broad width and high speed air-assisted planter were carried out.The effect of the structure of the profiling chisel sowing ditch device on the operation performance of the planter was studied.The results of field experiments showed that the operation performance of the profiling chisel sowing ditch device in sandy loam area of Xinjiang was better than that of the brown soil area with high water content in the middle and lower reaches of the Yangtze River.The sowing depth of winter rapeseed and winter wheat ranged from 18.1 to 18.4 mm and 26.8 to 27.9 mm,respectively,and that of spring rapeseed was 28.7 mm.The field sowing test results of rapeseed and wheat showed that the effect of soil depression caused by tractor tire indentation on spring rapeseed cultivation area was less than that on winter rapeseed cultivation area.Using passive disturbing soil device could effectively reduce the impact of tractor tire indentation on sowing depth stability and emergence effect.Meanwhile,the average seedling number of rapeseed and wheat in each row ranged from 10 to 14 and 35 to 36,respectively,and the variation coefficient of each row seedling number of rapeseed and wheat ranged from7.53%to 8.36%and 8.11%to 8.56%,respectively.The performance of the broad width and high speed air-assisted planter for rapeseed and wheat could meet the requirements of rapeseed and wheat emergence effect.Innovation point 1:The combination technique of combined type Venturi conveying seed and dome shaped distributor device discharging seed,and even seeding turbine even distributing seed was put forward.The air-assisted centralized metering device was developed,which could achieve broad width and high speed sowing adapting to the wide range of sowing quantity adjustment and obvious seed size difference of rapeseed and wheat under working condition of land slope.Innovation point 2:The profiling chisel sowing ditch device based on elastic deformation of profiling roller was developed,which could effectively guarantee the consistency and stability of sowing depth in broad width and high speed sowing operation. |
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