Mechanism Analysis And Experimental Research On Centrifugal Conical Disc Seed Metering Device

The precision seeding technology is a hot topic of widespread concern of researchers at home and abroad,because of the mechanical seeder are overall operating speed is not high,the seed shape and size requirements strictly,sowing rate of single seed needs to be improved,in recent years,some scholars began to pneumatic precision metering device was improved and research.The current study found that pneumatic metering device is excellent in adaptability,efficiency and uniformity with the traditional mechanical type metering device,however,the sealing structure is complex,appear in the air gap cavity leads to loss of air pressure,prone to leakage sowing phenomenon;highspeed operation and smooth in the field of soil not,if the air pressure is insufficient,the machine will cause the seed from shock intensified suckers have serious missed and repeated phenomenon;at the same time,to produce a single centrifugal blower is driven by the pressure of the power output shaft of the tractor,with the increase of seeding width with the more severe problems of energy consumption.At present,studies reported in the transformation of metering charging and discharging mode of domestic less related research for mechanism analysis and optimization of application documents,for the domestic farm population density,wide distribution,planting of large flexibility,put forward a kind of vertical centrifugal cone disc metering device.Compared with the traditional precision seeding technology: static accumulation-A-grain cleaning-seed-Guide,the way of the operation process of this change,namely the grain group into the cone to be given continuous centrifugal disk with the same kinetic energy and angular speed of the cone disc,with disc friction,moving cone disc push,regional corrugated motions,in order to discharge the same attitude.At the same time,the aim is to improve the working speed greatly,improve the quality stability and meet the requirements of precision seeding.Its research content and specific conclusions are as follows:(1)in the gravitational charging process of the traditional mechanical seed metering device,the increase of the grain position angle leads to the decline of the filling force linearly,which is the key factor to limit the efficiency of the filling.Therefore,it is an important way to increase the filling performance of the seed metering device by increasing the type of filling force and expanding the effective filling area.Through the analysis of the charging mechanism for discharging the grain in the vertical cone disc,studied the effects of filling factors on stress and effective filling area,key structure and key parameters are determined from the theory analysis,the cone angle in [0,23 °] to fill the large stress cone at 17.2 degree interval.Composite filling,stress()reached the maximum in grain filling setting;composite centrifugal push device after the stress has increased significantly,when the push plate number is 2,as the limit tensile force of centrifugal exert maximum efficiency;in the selected working speed range,grain position angle of about 8 degrees,composite filling stress reached the maximum,installation of centrifugal push filling feeding device and the stress increased nearly 4 times,at the same time,compared with the(static and dynamic)effective mode area [-5 °,16 °],the filling angle area has been enlarged.(2)using the discrete element numerical simulation of particle motion during centrifugal type wedge in the conical container of wedge particles are movement of the sliding flip conversion mechanism analysis,the study found that at the same speed conditions,with particle week angle increasing,the overall conversion of particles to the lateral attitude tendency is obvious,and the amount of transformation the lateral posture with the contact surface roughness increases.At the same time,the dynamic effect of cone disk speed on the particle switching characteristics is not obvious,and the particles in the moving cone centrifugal switching characteristics in motion by the geometric shape and size parameters of its own influence,therefore through quantitative method to describe the particle motion vector mark law and the attitude in the turnover process of distribution.Analysis of the stress and motion characteristics in the context of a specific particle,the research results mainly in the macro law to reflect,it is the prototype of a wedge-shaped granular corn grain type,in practice,the grain moisture content determines the adhesion between the particles,the particle particle collision,friction and other complex issues still need further study.Conclusion the mathematical model and the research under this condition can provide a theoretical reference for the metering device of key parts,cleaning device configuration and other agricultural engineering problems.(4)through simulation test and preliminary bench filling test,we can confirm that compared with the vertical cone tray seeding without pushing structure,pushing structure in the seed cavity can make full use of the centrifugal pressure of the upper population to improve seed filling performance.The results of comparative experiments show that the speed of moving cone with push structure can reach 30.1r/min,and the speed of single operation is 13km/h.In this range,the average miss seeding index is about 3.93%,which is 2.52% lower than that of no push structure filling mode.At the same time,reference [12],under the same experimental conditions,the operation speed test value increased by 3km/h compared with the finger clamp metering device,and under the same operation speed(9km/h),the miss seeding index decreased by 3.94%.The performance verification test shows that when the working speed is within 20.8 ~ 25.5r/min,the performance and indicators of the seed metering device perform better,while the fragmentation rate varies greatly,and the internal materials need further improvement.(5)the redundant cone structure was further simplified and perfected through the dynamic cone disk 3D model established by Solidwork.For the seeding mechanism and the early stage theoretical analysis,the material of the core components was improved.On this basis,using Modal module inside the ANSYS to make a preliminary set of 3D environment,add the corresponding constraints,fine mesh according to the corresponding algorithm for modal analysis of vibration simulation,the working process of generating dispatched cone disc in the first 6 order modal and natural frequency analysis,the external excitation frequency range is 0.009 ~ 0.017 Hz the moving cone disc,natural frequency and vibration characteristics of the assembly,the external adaptability improvement,further up the modal defects,improve the sealing degree and improve the operational performance of seedingapparatus.(6)through high-speed photography tracking record,the seed throwing track is parabolic,and the angle of delayed seed throwing is about 12 to 18 degrees.The probability of delayed seed throwing and timely seed throwing is more than 98%,while most seeds are concentrated in delayed planting area.The feeding test results showed that when the working speed of 15 ~ 30r/min range,the overall stability of grain delivery trajectory of horizontal displacement in the range of 22.8mm,and the dynamic between the cone disc groove and stationary disk for the existence of Caton phenomenon in the laboratory and extrusion.With the increase of the working speed of the metering device,the line speed of the horizontal component of grain discharge increases gradually,parabolic trajectory openings become larger when the working speed of 15 ~ 25r/min,the grain projection trajectory and landing position of intensive,when working speed is greater than 30r/min,the grain projection trajectory and landing position gradually discrete,and the change range,grain from the coefficient of variation increased significantly.This study provides a theoretical basis and practical reference for the optimization design of the seeding device of the centrifugal conical disc seed metering device and the structure of the guide tube.(7)through the metering device installation height,speed and with migration rate parameters to grain distance variation coefficient,multiple index and no seed index as the main performance indicators,reference to the national standard national standard GB/T6973-2005 "single particle(precision)method" drill test,bench test and single factor has many factors are.The single factor test results showed that the speed of seed metering device had a significant effect on seed filling performance,while the installation height of seed metering device was not the main factor affecting seed metering performance,and it had great influence on the coefficient of variation.The results of multivariate tests show that the working speed is 24.7/min,the metering device installation height of 48 mm under the condition of centrifugal cone disc metering device operation optimal performance,further validation test for parameters optimized,the measured coefficient of variation was 5.6%,the replay index was 7.1%,seed index was 4.9%,test the optimization results are consistent,the error in the acceptable range,precision seeding technology and agronomic requirements.