气吸振动盘式精密排种装置理论与试验研究
本文选题:气吸振动 + 精密排种装置 ; 参考:《江苏大学》2013年博士论文
【摘要】:精密排种装置是实现精密播种作业的关键设备,其性能优劣直接关系到作物生产的产量和品质。目前,超级稻穴盘育苗精密排种装置还处于探索研究阶段,现有的水稻排种装置大都属机械式,伤种较严重,且每穴播种达3-5粒,难以满足超级稻种植对播种技术的农艺要求(2±1粒/穴,低伤种率),因此,急需开展超级稻穴盘育苗精密排种装置的理论与试验研究。本文以设计的新型气吸振动盘式精密排种装置为研究对象,通过振动理论、计算流体动力学、离散元法、机构学、实验优化等理论,并结合先进的计算机仿真技术深入研究播种过程中排种装置机构运动、振动激励和气力对超级稻种子的作用机理及种群的运动规律、连续播种过程最佳吸种效果的参数组合,提出了精密播种理论,主要研究工作包括: (1)采用专业测量仪器对三个品种超级稻芽种基础物理特性参数进行测试和分析,得到芽种的三轴几何尺寸分布概率、千粒重、密度、摩擦系数、休止角、恢复系数和力-位移变化关系,为离散元仿真和排种装置吸种部件设计提供依据。 (2)运用FLUENT对排种装置气流场进行研究:①分析吸种盘气流场分布规律,得出影响气流场的主要因素为吸孔孔径、真空负压值,得到均匀稳定流场的最佳结构及工作参数;②分析气流场中种子颗粒受力影响因素,得出其主次顺序为种子与吸孔的距离、种子姿态、真空负压值、吸孔孔径;建立种子受力数学模型,分析得出:真空负压值与孔径应合理匹配,小孔径需较大的真空负压值,高度方向的种子最容易被吸附;真空负压值为3~5kpa范围内,吸孔孔径为1.5mm~2.0mm时,吸孔吸附距离范围为0.34mm~1.90mm;③对吸种盘正压气流场进行模拟,得出流量对吸种盘正压气流场影响大,随着流量增加,吸孔口气流流速急剧增大,种子受到气流吹力增大,内板厚度对正压气流场分布和流量几乎无影响;④进行气流场流量测定及种子颗粒吸附试验,试验结果与FLUENT模拟值基本吻合,表明数值模拟结果的正确性。 (3)进行排种装置的机构运动分析:①采用ADAMS对振动种盘机构运动进行分析,得到机构动力源的变化规律:随着频率和振幅的增大,最大驱动扭矩逐渐增大;②基于机构学理论,研究符合水平调节要求的并联机构,对一平移两转动并联机构进行型综合,设计水平调节机构,获得机构位置关系和精度模型;③建立携种过程种子颗粒受力数学模型,推导带动吸种盘运动的机械手动力学特性要求。随着负压值的增大,机械手临界加速度增加。长度方向吸附的种子最容易发生掉落,机械手设计时应满足长度方向不发生掉落的条件;④建立种子颗粒与吸种盘的碰撞运动数学模型,得出种子颗粒不被碰离吸种盘面板的弹回临界速度与负压值的关系。随着负压值增大,种子颗粒弹回临界速度增加。长度方向碰撞的种子最容易发生弹回掉落,当碰撞弹回速度大于临界弹回速度时,种子将脱离气流场约束并弹离吸孔。 (4)基于离散元理论,研究振动种盘内种群运动,得出:①单颗粒种子运动具有波动性,受种群颗粒间约束力的相互作用,种群的运动呈规律性变化;②随着振动种盘振动频率和振幅的增加,种群竖直方向平均位移、平均速度和颗粒受力逐渐增大,种群抛掷运动的激烈程度增加,相对空间分布密度逐渐变小,增大频率和振幅能有效增大种群抛掷高度。单层种群抛掷高度、颗粒平均法向力和平均切向力大于其他种层厚度种群,其他种层厚度种群的竖直方向平均位移和平均速度、颗粒间平均受力及种群空间离散程度受种层厚度的影响较小。种子颗粒受到的作用力最大值小于0.03N,得出振动种盘的运动对种子损伤极小;③分析连续播种过程振动种盘内种子逐渐减少的变质量系统种层厚度与振动种盘振动参数的关系,建立排种装置工作参数与吸种距离(吸种盘面板与种层表面之间距离)之间的数学模型。得出影响种群抛掷高度的因素主次顺序为:振动频率、振幅、种层厚度,振动频率与振幅应合理匹配;仿真模拟倾斜状态振动种盘内种群运动,振动种盘倾角越大时种群运动均匀性越差,倾角越小对振动种群空间分布均匀性越有利;④基于CFD-DEM耦合理论,应用FLUENT-EDEM耦合方法仿真模拟了排种装置吸种过程,得出了参数变化规律。 (5)研制一种新型气吸振动盘式精密排种装置试验台,并开展台架试验。①进行单因素试验和正交试验,着重分析真空负压值、吸孔孔径、振动种盘振动频率、振幅、吸种距离等因素对播种性能指标的影响,得出影响合格率的因素主次顺序为:吸种距离、振动频率、振幅、真空负压值、吸孔孔径;影响重播率的因素主次顺序为:真空负压值、吸孔孔径、吸种距离、振动频率、振幅;影响空穴率的因素主次顺序为:吸种距离、真空负压值、吸孔孔径、振动频率、振幅;吸种距离和频率对播种合格率有显著影响,真空负压值和吸孔孔径对重播率有显著的影响,吸种距离和负压真空值对空穴率有显著影响。②建立排种装置工作参数与播种性能指标之间的数学模型,进行遗传算法的多目标优化,得到最优解:真空负压值3.68kPa,吸孔孔径1.84mm,振动频率10.90Hz,振幅4.09mm,吸种距离3.92mm,并进行试验验证。③对不同品种超级稻进行播种试验,证明排种装置对不同品种超级稻芽种具有较好适应性。采用排种装置对芽种进行播种育苗试验,证明排种装置不损芽。通过对播种后的穴盘进行育苗后发现,该排种装置能满足超级稻种植的育苗要求。试验结果与理论分析相一致,为精密排种装置的设计提供理论依据。
[Abstract]:Precision seed metering device is the key equipment to realize precision seeding operation. Its performance is directly related to the yield and quality of crop production. At present, the precision seed metering device for super rice seedling raising is still in the stage of exploration and research. The existing plant seed metering devices are mostly mechanical, and the injury species is more serious, and 3-5 seeds per hole can not be satisfied. Therefore, it is urgent to carry out the theoretical and Experimental Research on the precision seed metering device for super rice seedling raising and seedling raising. In this paper, a new type of pneumatic vibrating disc type precision seed metering device is designed as the research object. Through the vibration theory, the fluid dynamics, the discrete element method, the mechanism and the reality are calculated. According to the theory of optimization and so on, combined with the advanced computer simulation technology, the mechanism of the arrangement of plant mechanism, the mechanism of the action of vibration and gas on the seed of super rice and the movement rule of the population, the combination of the optimum seed sucking effect in the continuous sowing process are studied. The theory of precision seeding is put forward, and the main research work includes:
(1) to test and analyze the physical parameters of three varieties of super rice sprouts based on professional measuring instruments, the probability of geometric size distribution of three axes, 1000 grain weight, density, friction coefficient, repose angle, recovery coefficient and force displacement change are obtained, which provide the basis for the design of the discrete Yuan Fangzhen and seed metering device.
(2) using FLUENT to study the airflow field of the seed metering device: (1) analysis of the distribution law of the flow field of the suction disc, the main factors affecting the airflow field are the aperture of the suction hole and the vacuum negative pressure value, and the best structure and working parameters of the uniform stable flow field are obtained. Secondly, the influence factors of the force of the seed particles in the airflow field are analyzed, and the order of its primary and secondary is the seed. The distance between the seed and the hole, the attitude of the seed, the vacuum negative pressure and the aperture of the hole, the mathematical model of the force of the seed is established. It is concluded that the vacuum pressure value should match the pore size reasonably, the small aperture needs the larger vacuum negative pressure, the high direction of the seed is most easily adsorbed; the vacuum vacuum pressure is within the range of 3 ~ 5kpa, and the aperture of the suction hole is 1.5mm to 2.0mm, The range of absorption distance of the suction hole is 0.34mm ~ 1.90mm; thirdly, the positive air flow field of the sucking disc is simulated. It is found that the flow rate has great influence on the positive air flow field of the seed suction disc. With the increase of the flow rate, the flow velocity of the suction hole is increased sharply, the seed is increased by the air blowing force, and the thickness of the inner plate has little effect on the distribution and flow of the positive pressure flow field. The results of field flow measurement and seed particle adsorption test agree well with the FLUENT simulation values, indicating the correctness of the numerical simulation results.
(3) the mechanism motion analysis of the seed metering device: (1) the motion of the vibratory disc mechanism is analyzed by ADAMS, and the change rule of the mechanism power source is obtained: with the increase of frequency and amplitude, the maximum driving torque is gradually increased; secondly, based on the mechanism theory, the parallel mechanism which meets the requirements of the horizontal adjustment is studied and the two rotation of a horizontal shift is carried out. The joint structure is integrated, the horizontal adjustment mechanism is designed, the position relationship and the precision model of the mechanism are obtained. Thirdly, the mathematical model of the force of the seed particles in the carrying process is set up, and the mechanical mechanical properties of the mechanical hand are derived. With the increase of the negative pressure, the critical acceleration of the manipulator increases. The seeds with the length direction are the easiest to adsorb. When the manipulator is dropped, the manipulator should meet the condition that the length direction does not fall when the manipulator is designed. (4) establish the mathematical model of the collision motion between the seed particles and the seed suction disc, and get the relationship between the critical velocity and the negative pressure of the seed particles not being touched from the suction plate panel. With the increase of the negative pressure, the critical velocity of the seed particles increases. When the impact velocity is greater than the critical rebound velocity, the seed will be released from the gas flow field and will be released from the suction hole.
(4) based on the discrete element theory, the movement of the population in the vibrating seed disc is studied. The results are as follows: (1) the motion of single grain seeds is fluctuant, and the movement of the population is regularly changed by the binding interaction between the particles. Secondly, the average displacement of the vertical direction of the population, the average velocity and the force of the particle with the increase of the vibration frequency and amplitude of the vibrating seed disc Gradually increasing, the intensity of the population throwing movement increases, the relative spatial distribution density gradually becomes smaller and the increase of frequency and amplitude can effectively increase the height of the population throwing. The single single population throws the height, the average normal force and the mean tangential force of the particle are larger than those of the other layer thickness, and the average displacement of the vertical direction of the species with the thickness of his seed layer is peaceful. The average force between particles and the degree of spatial dispersion of the population are less affected by the thickness of the seed layer. The maximum force of the seed particles is less than 0.03N, and the motion of the vibratory disc is very little to the seeds. Thirdly, the thickness of the seed layer of the variable mass system and the vibration type disc vibration of the continuous sowing in the continuous sowing process are analyzed. The relationship between the dynamic parameters and the mathematical model between the working parameters of the seed metering device and the distance of the seed suction (the distance between the seed plate and the surface of the seed). The order of the factors that affect the height of the throwing height of the population is the vibration frequency, amplitude, the thickness of the seed layer, the vibration frequency and the amplitude, and the simulation and Simulation of the incline vibration species in the disc. The worse the population movement is, the worse the population movement uniformity is, the less the inclination is, the more favorable to the uniformity of the spatial distribution of the vibrating population. (4) based on the CFD-DEM coupling theory, the FLUENT-EDEM coupling method is used to simulate the seed sucking process of the seed metering device, and the variation of the parameters is obtained.
(5) develop a new type of air suction vibrating disc type precision seed metering device test bed and carry out a bench test. (1) single factor test and orthogonal test are carried out to analyze the influence of vacuum negative pressure value, hole suction aperture, vibration frequency, amplitude and distance of seed suction on the performance index of sowing, and the order of factors affecting the qualified rate is obtained. The main and secondary factors affecting the replay rate are vacuum negative pressure, aperture, distance, vibration frequency and amplitude; the main and secondary order of the factors affecting the hole rate are suction distance, vacuum pressure value, aperture, vibration frequency, amplitude, distance and frequency of sucking. The rate has a significant influence on the qualified rate of sowing, the vacuum negative pressure value and the aperture of the suction hole have a significant influence on the replay rate, the suction distance and the vacuum value have a significant influence on the hole rate. Secondly, the mathematical model between the working parameters of the seed metering device and the performance index of the seeding is established, and the optimal solution of the vacuum negative pressure is obtained by the multi-objective optimization of the genetic algorithm. Value 3.68kPa, hole aperture 1.84mm, vibration frequency 10.90Hz, amplitude 4.09mm, seed distance 3.92mm, and test verification. 3. Sowing experiments on different varieties of super rice proved that seed metering device has better adaptability to different varieties of super rice bud. Seed planting experiment with seed metering device is used to prove that seed planting device does not damage bud. After seedling raising after seeding, it is found that the plant can meet the requirements of the cultivation of super rice. The result of the experiment is consistent with the theoretical analysis, and provides a theoretical basis for the design of precision seed metering device.
【学位授予单位】:江苏大学
【学位级别】:博士
【学位授予年份】:2013
【分类号】:S223.25;TH112
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