| Wheat seed and rapeseed are important grain and oil crops in China,the acreage of rapeseed is relatively stable as approximately7,000,000hectares in2012, but the level of mechanization of its planting is only14.51%; The acreage of wheat seed is increasing very year, which approaches to24.27million hectares in2012, the level of mechanization of its planting is86.52%, but majority of it is based on mechanized drilling. Rapeseed and winter wheat are autumn crops, especially in the Yangtze River basin,rapeseed and wheat sowing period are adjacent to each other,the rapeseed’s planting process is similar to the wheat seed’s.Anewdual-purpose both for wheat seed and rapeseed pneumatic precision seeder was developed to improve the utilization of the planterand plant both the rapeseed and wheat seed with only one seeder.Based on the working principle of the sucking section with negative airflow pressure and the releasing section with positive airflow pressure and the integrated pneumatic precision seed technology,a dual-purpose both for wheat seed and rapeseed pneumatic precision metering devices was proposed with innovationbecause of the extremely physical properties differences of the rapeseed and wheat seed, and on this basis,the pneumatic precision metering system and mechanism of dual-purpose for wheat seed and rapeseed were researched.The main contents include:(1) The test and analysis of mechanical and physical properties and parameters for wheat seed and rapeseed were carried out, and the basic size of seed shape,the thousand grain weight of seeds,natural angle of repose for seeds,coefficient of friction of the seeds were obtained,which could provide the theoretical basis for the main structural parameters design,according to the working principle of the sucking section with negative airflow pressure and the releasing section with positive airflow pressure,a kind of rapeseed and wheat seed combined type pneumatic precision metering systems was developed and the structural parameters and operating parameters were analyzed.(2)The releasing process of the seeder both for rapeseed and wheat was analyzed,the kinematics and dynamics model of the seeds when they were in the sucking section,taking section and releasing section were established with the help of mechanical analytical method and got the discipline of how the working index affects the moving seed and analyzed the situation when the seed would not slide or roll while it was moving.The analysis showed that:the filling angle y of seed filling area,the rotating speed ω of seed plate,the radius r of seed plate,the angle of guiding strip90°-θ had a relationship with the friction coefficient f1between seeds and guiding strip and the friction coefficient f2among seeds;The negative pressure of sucking and taking had a relationship with the mass of seed m, the size of seed shape,the diameter d of seed plate,the diameter dx of hole carrying single seed, the angle a of sucking and the rotating speed co of seed plate;The positive pressure of sucking and taking had a relationship with the mass of seed m, the diameter d of seed plate,the diameter dx of hole carrying single seed and the rotating speed ω of seed plate.(3)The test for dual-purpose pneumatic precision metering device both for wheat and rapeseed was carried out in a system way. The hole carrying seed on the seed plate was identified that it was straight cylindrical bore, the diameter of the hole for carrying rapeseed was1.2mm and1.5mm instead for wheat seed plate;The guiding stripes on the seed plate for wheat were a rectangular shape and they were arranged like L.Tests showed that the seeder’s qualified index,multiple index, missing index were affected by rotating speed of the seed plate,the positive and negative pressure significantly.The test results showed that when the rotating speed of the seed plate was18r/min,the negative pressure was2200Pa,the positive pressure was400Pa,the qualified index for seeding rapeseed was90.02%,the missing index was2.59%;when the rotating speed of the seed plate was15r/min,the negative pressure was2300Pa,the qualified index for seeding wheat was90.62%,the missing index was2.96%with guiding strips fixed on the seed plate.(4)Based on the analysis of the common technology and structural features of a public body of dual-purpose pneumatic precision metering for both wheat seed and rapeseed a kind of dual-purpose seeder with guiding strips fixed on the seed plate and its structural of the hole carrying seed was developed for its dual-purpose pneumatic precision metering.Studies had shown that:when the negative pressure was2900Pa,the average qualified index for wheat seeding with guiding strips fixed on the seed plate relatively increased by0.76%and the missing index decreased by38.61%; when the negative pressure was900Pa,the positive pressure was500Pa,the qualified index for rapeseed seeding with guiding strips fixed on the seed plate relatively increased by3.72%and the missing index decreased by8.58%;while the rotating speed of seed plate inside the dual-purpose pneumatic precision metering device was20r/min-30r/min, the seeding performance of the dual-purpose pneumatic precision metering device could meet the requirement of sowing for wheat seed and rapeseed,and there were no mechanical damage to the seeds while the guiding strips were fixed on the seed plate.(5)The process of filling,sucking,taking,releasing in the seeder with guiding stripe fixed on the seed plate was analyzed and observed based on the with the high-speed camera technology.Research results showed:while the rotating speed of seed plate inside the dual-purpose pneumatic precision metering device was10r/min-45r/min, the seeds filling angle and the rotating speed had a linear correlation,the filling performance improved while the seed plate fixed with guiding stripes;The height of sucking point had a relationship with the height of the seed inlet point, when the height of the seed inlet point was47mm,the height of sucking point had a best linear correlation with the rotating speed;The path length of taking section had a relationship with the rotating speed,the faster of speed,the shorter of the path length of taking section;The releasing trace and the path length of releasing had a relationship with the rotating speed of the seed plate,the radius of the seed plate and the falling time of the seed.The faster of the rotating speed,the better of degree of fitting for the releasing trace and the closer to the parabola when it was doing a horizontal cast movement,the width of the releasing outlet would be40mm.(6)A simulation of the seed flow movement was carried out with the help of EDEM,the velocity,displacement,force and time of the seed granules and granule group was conducted in a exploratory way:when the rotating speed didn’t get changed,the displacement of the granules group got a regular cycle changing with time,the force of the granule group would be stable with the time went on,the velocity of the granule group would get changed within a narrow range after the seeds became to granule group,which were stable overall,the simulation results with the results obtained consistent high-speed camera;Meanwhile,a simulation of the air flow inside the seed chamber was carried out based on the software named of ANSYS-fluid module ANSYS/CFX and FUENT,defined the velocities of the air flow with the different holes shape,and when the hole was drawn straight cylindrical bore hole shape,its airflow velocity changed in a uniform way,which could match the requirements of the uniform air negative flow for the seeder.(7)The test for the seeding system in field was carried out,results showed that:every row of the output volume had a good consistency,the variable coefficient of each row was under10%when seeding rapeseed and wheat seed;Meanwhile,the test and analysis of the seedling rate in field were carried out,the test results showed that rapeseed planting density could be29,200/acre;wheat planting density could be39,200thousand/acre,the tiller number was about3to10,after that it could be about254,800/acre,which could match the agronomic requirements of wheat and rapeseed.Field production test showed that:the pre-production of rapeseed would be202kg/acre;the pre-production of wheat would be480kg/acre. Innovation Point1:Using the basic principles of positive and negative pressure modular, developed a suitable particle size combined use of two different type Pneumatic precision seeder;Innovation Point2: Innovatively proposed a dual-purpose seeder within guiding stripes and holes inside to match the purpose of a a pneumatic precision metering device for dual-purpose use;... |
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