【作者】 李鑫；

【导师】 冯晓静；

【作者基本信息】 河北农业大学 ， 农业机械化工程， 2018， 硕士

【摘要】 随着我国玉米规模化生产的不断发展,对玉米单产水平的关注逐渐提高,对玉米的播种质量提出了更高的要求,即在高速度、高效率、高密植的条件下,实现玉米高质量精密播种,因而对玉米播种机的核心部件精密排种器提出了更高的技术要求。目前国内的气力式和机械式的玉米排种器作业速度只能达到6~8 km/h,难以实现高速作业。因此针对此问题论文将以勺轮式排种器为研究对象,以提高排种器的作业速度为研究的切入点,通过研究籽粒在各个运动过程的受力,对主要参数进行优化,以改善排种器的排种性能作为设计目标,研发一种新型的双勺轮式玉米精密排种器:(1)双勺轮玉米精密排种器在传统的勺轮式排种器基础上进行研究,将双勺轮和双面递种轮相融合,通过降低排种器的转速,保证籽粒在勺轮中的稳定性,降低漏播指数,提高清种能力,降低重播指数,提高排种器在高转速条件下的排种性能。(2)通过分析籽粒充种、清种、递种、护种、投种和在种床上的受力、运动情况,确定排种器的基本形式。建立排种器在各个运动过程的数学模型,通过理论计算,确定其主要结构参数:排种器的隔板展角为75°、初始递种位置为55°~75°、投种口位置为40°~55°和极限转速为73.1 r/min。(3)运用离散元软件EDEM仿真分析,验证籽粒以填补空间、相向运动和同向运动三种运动方式进行充种,其充种率可以达到100%。仿真结果表明递种位置决定清种效果;投种前籽粒在递种轮中发生滑动、跳动;籽粒在投出后做平抛运动,在种床上发生弹跳、滚动和滑动。(4)对排种器进行仿真分析、台架试验和田间试验,通过投种位置、排种器转速单因素试验确定了排种器的最佳投种位置范围40°~55°,与理论计算相吻合。对株距均匀性进行探究,分析转速波动、振动和种床地表形态的影响,得出转速通过影响抛距从而影响株距均匀性;有益振动可以提高排种性能,提高株距均匀性;种床地表疏松有利于降低籽粒在种床上出现弹跳、滚动和滑动,提高株距均匀性。(5)通过对递种位置、籽粒尺差和排种器转速进行试验,探明高速条件下漏播和重播陡增的原因,对试验结果进行回归分析,得到合格指数的控制方程,并对其预测进行试验验证,表明控制方程预测精度较高。(6)进行中低速和高速的台架试验和田间试验,试验结果表明在中低速条件下,双勺轮排种器的工作性能和指夹式、单勺轮相接近,均高于87%;作业速度为10.152km/h时,双勺轮排种器的合格指数为86.63%,明显高于单勺轮的80.35%和指夹式的80.21%,满足《单粒(精量)播种机技术条件》中要求的80%。更多还原

【Abstract】 With development of China’s corn mass production and high-level concern over corn yield,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 corn seed-metering device.The top working speed of seed-metering was between 6km/h and 8km/h in china,the main factor was seed-metering performance at high working speed and it is hard to realize high speed sowing.To solve this problem,a new type corn precision seed-metering device with double spoon wheel was developed,which could improve single grain performance:(1)The double spoon wheel corn precision seed-metering device is studied on the basis of the traditional type spoon wheel seed metering device,which combines the double spoon wheel with the double delivery wheel.To ensure the stability of the grain in the spoon wheel and induce the qualified index by reducing the rotational speed of the seed-metering device.(2)The basic form of seed-metering device is determined by analyzing the force and the movement about the process of seed filling,seed cleaning,seed delivery,seed protecting and seed throwing.The mathematical model of the seed-metering device in each movement process is established.(3)Through theoretical calculation,the main structural parameters are determined: the bulkhead angle of the seed metering device is 75 degrees,the initial delivery position is 55 to 75 degrees,the position of the seed throwing is 40 to 55 degrees,and the limit rotational speed is 73.1 r/min.Through the simulation analysis of the discrete element software EDEM,it is proved that the seed filling is filled with three ways of filling space,opposite direction movement and same direction movement,and the rate of seed filling can reach 100%.The test shows that the position of the seed delivery determines the effect of the seed clearing,the grain slips and jumps in the seed delivery wheel before the seed throwing and the grain bounces,rolls and slides on the seed bed after throwing.(4)Several parameters were fixed including the best position of the seed throwing,the optimum range of rotational speed and the most optimal position of the seed delivery by single factor experiment of position and speed of spoon-wheel,the reason why seed-missing index decreased sharply was found out at high rotational speed by comparison between seed-missing index and seed-filling index.(5)The effects of speed fluctuation,vibration and seed bed topography are analyzed to research on the homogeneity of plant spacing.The experimental results show that the rotational speed can affect the spacing of the plant spacing by throwing distance,the beneficial vibration can improve the performance of the seed row and the uniformity of the ground surface is beneficial to the improvement of the uniformity of the plant spacing.The simulation was done to get governing equation of qualified index by regression analysis,and accuracy of governing equations’ prediction was validated.(6)The results show that the performance of the double spoon wheel seeding device is close to the picker finger and single spoon wheel under the medium and low speed conditions.When the speed is 10.152km/h,the qualification index of the double spoon wheel seeding device is 86.63%,which is obviously higher than the picker finger and single spoon wheel.The operation effect of double spoon wheel seed-metering device meets the requirement of 80% in the technical condition of single grain(precision)seeder.更多还原