Design And Experiment Of Wheat Seed-Metering Device With Stirred Trapezoidal Hole Wheel

Wheat is an important food production material in China,and it is of great significance to maintaining national food security by ensuring its high and stable yield.The application of external grooved wheel seed-metering device in wheat drill is relatively large,and it has pulsatility under low speed operation conditions,which has a significant impact on the stability and uniformity of seed-metering.This study aims at the problems existing in the grooved wheel seed-metering device,based on the characteristics of wheat seed materials,a wheat seed-metering device with stirred trapezoidal hole wheel was designed.The stirring ring of the hole wheel was used to guide the seed arrangement and exert disturbance on the population,controlling the number and distribution status of the seed in the trapezoidal hole.The seed chute structure allows the seed to be smoothly and evenly cast,ensuring the stability and uniformity of the seed amount.The main work of this study is as follows:(1)Measurement of material properties of wheat seed and calibration of simulated contact parameters.The material properties of Jimai 22 seed were measured.A wheat particle model was constructed in the EDEM software using the 5-sphere combination method and the physical properties and intrinsic parameters of the simulation model was defined.Based on the constructed wheat particle model,the contact parameters between the wheat particle and the material were recalibrated.The results showed that the simulated contact parameters between the wheat particle and the material were basically consistent with the actual experiment values,and could be used for subsequent simulation experiment of wheat seed and seed-metering device.(2)Design of the structure and key components of the seed-metering device.The overall structure and working principle of the seed-metering device were described,and a kinetic model for the seed-filling and seed-feeding process of the seed-metering device was established.Based on the material characteristics of the Jimai 22 seed,the key structural parameters of the seed-metering device were designed according to the posture probability and arrangement state of the seed-filling into the mold hole.The value range of the trapezoidal hole bottom was 3.49～4.41mm,the seed-feeding groove angle range was35°～45°,and the stirring ring angle range was 30°～48°.(3)Simulation experiment of working performance of seed-metering device.Taking the lower bottom of the trapezoidal hole,the angle of the seed-feeding groove,and the angle of the stirring ring as the experiment factors,and using a 3-factor and 3-level orthogonal rotation combination experiment,under the conditions of the advance speed of the drill of4km/h and the rotation speed of the seed-metering wheel of 25r/min,the optimal combination parameters were obtained as follows:the lower bottom of the trapezoidal hole was 4.157mm,the angle of the seed-feeding groove was 42.295°,the angle of the stirring ring was 45.3°.Under this combination,the average seeding rate was 6.151g/s,and the coefficient of variation of seeding uniformity was 25.758%.The average kinetic energy of the population under the disturbance of stirring ring with inclination angles of 45.3°,40°,48°,and 30°was higher than that without seed stirring ring,respectively 132.65%、124.23%、117.48%、114.73%。(4)Performance bench and soil bin experiment of seed-metering device.The error of the results of the bench and soil bin validation experiment is within a reasonable range,and the simulation prediction model is reliable.At a rotational speed of 10～80r/min,the metering rate of the seed-metering device was 155.44～946.96g/min,the space utilization rate of a single hole was 61.34～80.59%,the coefficient of variation of the stability of the metering rate was less than 4.0%,and the seed breakage rate was less than 0.2%.The active working experiment of the seed-metering device was conducted in the bench and soil bin.The experimental results showed that under the conditions of the wheat drill with a seeding rate of 150 to 300 kg/hm~2 and a forward speed of 4 to 6 km/h,the maximum error rate between the metering amount of the metering device and the amount of the active metering device prediction model obtained from the bench experiment was not more than 5%,The coefficient of variation of the stability of the seeding rate under each gradient was less than 4.0%,and the seed breakage rate was less than 0.2%;the maximum error rate between the metering amount of the metering-device and the amount of the active metering-device prediction model obtained from the soil bin experiment was not more than 9%,the stability variation coefficient of the metering rate under each gradient was less than 4.0%,and the uniformity variation coefficient of the metering is less than 30%,which meets the design requirements of the mechanical wheat metering-device.