Design And Experimental Research Of The Pneumatic Maize Precision Seed-metering Device With Combined Holes

With development of China’s maize mass production and high-level concern over maize yields, higher demand on seeding quality had been drawn by large-scale manager, specially, precision planting was realized under the condition of high density, high speed and high efficiency, which could be met by high quality maize seed-metering device. The top working speed of pneumatic drill was8km/h in China, the main factor was poor seed-filling performance at high working speed which limited improvement of working speed. To solve this problem, A new type pneumatic maize precision seed-metering device with combined holes was developed, which could improve single grain performance and population mobility.There was no seed stirrer which was used in traditional pneumatic seed-metering device in the pneumatic maize precision seed-metering device with combined holes, holes in feeding disk had the functions both seed-filling and seed-stirring, population mobility was improved and internal friction was reduced between seeds in seed-filling area, in addition, it is easier for seed to attach on the surface of hole with the action of positive pressure, so the seed-filling performance was improved of seed-metering device in high working speed. The seed-metering device had simple structure, worked stably with excellent performance at high speed.The conclusion was validated that seed-filling index rose with the seed-stirring strength increased to some extent by simulating and analyzing with EDEM and bench test, meanwhile, the basic structure of plate was fixed based on the conclusion. Parameters of hole were theoretically calculated in pneumatic maize precision seed-metering device with combined hole, a mathematical model was established of seed-stirring process, and the main structure parameter of the plate was determined, the most optimal parameter of air intake was obtained with FLUENT.A coupling model was established of maize seed and its physical property parameter was calibrated, two phases gas-solid coupling model was analyzed of pneumatic maize precision seed-metering device with combined hole with EDEM and FLUNET based on deterministic particle-trajectory model, the distribution of flow field and force situation were obtained in operation, and the effect of operating parameter on seed-filling performance was examined from the standpoint of mechanics, which provided evidence for the optimization of hole parameter.Several parameters were fixed including the minimum pressure of seed-metering device, the most optimal working pressure and the speed range by single factor experiment of operation pressure and speed of plate, the reason why seed-missing index decreased sharply was found out at high speed by comparison between seed-missing index and seed-filling index. Several parts of seed-metering device were improved including seed-eliminating machinery, plate and seed-dropping machinery by simulation and test, meanwhile, two-factor experiment of operation pressure and speed of plate was done to get governing equations of qualified index by regression analysis, and accuracy of governing equations’ prediction was validated., otherwise, two-factor experiments of operation pressure and seed-eliminating gear operation pressure and speed of plate were done respectively and the most optimal positions of seed-eliminating knife were fixed at any speed of plate and under any pressure, A field trail was done both at lower speed, medium speed and high speed and the result indicated that the operation performance was stable of seed-metering device at each speed, the qualified index reach up to95%when the working speed was10.9km/h.