| Notoginseng is one of rare medicinal herbs in China, and it is mainly grown in Yunnan Province. Market demand of notoginseng is very large, and hence, until December 2014, the planting area of notoginseng has reached 40000 hm2. At present, the main planting pattern is through manual operation, and the labor intensity is very high and the sowing quality is discrepant. However, there is no precision seeding device suitable for notoginseng. Therefore, the mechanization planting of notoginseng has important practical significance. Notoginseng is planted on small plots of land, the planting density and the requirement of seeding precision are high, so we designed a small sized precision metering device. The liquidity of the seeds is not good and the shape of seeds is irregular for notoginseng, so we chose the pneumatic seed-metering device to adapt to the characteristics of the seeds accordingly. In order to meet the precision seeding requirements of notoginseng planting, a unique pneumatic cylinder-type precision metering device was designed, which can effecitively solve the problem, such as structure complex, positive and negative exchange interfere. This device integrated the features of vacuum suction, insulated pressure for seed-clearing and zero speed of seed dropping. According to the characteristics of seeds and planting requirements, determine the basic size of seed metering device.Internal flow field analysis of seed metering device to determine hollow shaft progress between stomatal aperture and hole and the hole distribution, and seed experiment was carried out.At the same time in order to improve the qualified rate of seed, seed filling link add vibration and air blowing, and has carried on the simulation and experiment.Concrete study content as follows:(1) To experimental measurement on the basis of the basic parameters of notoginseng seeds and planting requirements, determine the suction drum metering device suction hole size and location.The CFD simulate working condition of suction seed metering device, to determine the hollow shaft into the hole size and location, in order to realize the whole cavity flow field stable in the body.(2) To realize zero velocity for metering process, this article through analyzed dropping process, and determines the unique angle and clamp installed device speed linear relationship, so as to realize under the condition of the different speed regulating absolutely clamp installed Angle to throw to achieve zero speed.(3) The EDEM-Fluent software simulated and predicted notoginseng seeds suspension speed under different volume, and the feasibility of this method is proved by experiment and theory, and puted forward a new measurement method for this, at the same time for the suction drum metering device provides the basis for the determination of negative pressure value.(4) At homemade seeding test-bed, we studied the seeding performance. Experiment design used three factors five levels quadratic orthogonal rotation combination test method, vacuum degree, speed, and suck angle as influencing factors, qualified index,multiple index,missing index as the objective function.Established between the factors and the objective function of the mathematical model, analyzed the various factors on the influence law of the objective function, optimization of the vacuum degree is obtained. Speed and angle of the suction of the best parameter combination, namely vacuum degree during 660-720 pa, forward speed in 0.72-0.76 m/s,when angle of the suction is 20°, can obtain qualified index greater than 90.2, missing index is less than 4.9, multiple index is less than 5.3.(5) In order to further improve the performance of seed metering device, we added vibration and air blowing on the box. By EDEM simulated vibration, with Fluent simulated gas blowing, we found between the two ways could reduce the population in the transient friction, advantageous to the filling.The DEM coupling CFD method simulated the vibration method combining the gas blowing on the properties of filling effect, the results show that the vibration frequency is 125 Hz, wind pressure of 2.25 kPa, vibration angle 45°populations within the transient friction force between the youngest, filling effect is best.(6)Vibration frequency, vibration angle, wind pressure as factors, qualified index,multiple index,missing index as the objective function, three factors five levels orthogonal experiment method is adopted to experiment, and adopted the Design-Expert software for data analysis and optimization, the results show that the vibration frequency, wind pressure as significant factors, the vibration angle as the significant factors, the optimized result is the vibration frequency 105 Hz, wind pressure of 2.25 kPa, vibration angle 45°. At this time, qualified index 94.78, missing index 4.49, multiple index 0.95 are all in agreement with the simulation results. |
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