气助式低频超声雾化喷头的设计及喷雾试验

发布时间：2018-07-11 10:33

本文选题：喷头 + 超声雾化　；参考：《江苏大学》2017年硕士论文

【摘要】：超声雾化喷头比起普通压力喷头,能够产生尺寸更加细小的雾滴,使得其在满足农作物生长需求的同时,达到了节约水资源和减少农药使用的目的。对于农药或者营养液等粘度较大的液体,超声雾化喷头能够更容易地雾化,因而它在农业施肥领域具备得天独厚的优势。为了解决现有的技术问题,进一步细化雾滴粒径并提高喷雾的均匀性,增大喷雾角度,增强喷雾抗干扰能力,本文采用计算机建模与有限元分析结合的方法,设计了气助式低频超声雾化喷头,并在此基础上发展了带有涡流齿轮的设计方案及带有金属悬浮球的二次雾化设计方案。喷头的基本结构包括机械振动结构和流体结构,通过使用计算机软件建模和有限元模拟仿真相结合的方法对喷头进行了设计验证。喷头的机械振动结构包括超声换能器和超声变幅杆两大部分,通过理论计算得出结构中各个尺寸的具体数值,并给出了相应的数学计算过程及计算结果。采用模态分析、谐响应分析等CAE方法对设计的结构进行虚拟仿真,并将仿真结果与理论设计值相比较,验证设计方案,从而确定结构各部分的最终参数。采用流体仿真的方法对喷头的流体结构进行设计分析,通过观察仿真结果中喷头内部气流的运动情况和在喷口处的射流情况来验证结构设计的可行性。根据设计参数制造出喷头样机,并对样机的具体特性进行试验测试。对喷头样机的阻抗特性进行分析,测出样机的谐振频率为57984Hz,与喷头的理论设计频率60KHz相差3.4%;得到喷头换能器的其他关键参数,为喷头驱动电源的设计提供了设计依据。对喷头变幅杆的端面振幅及悬浮球的振幅进行了测量,得出电源电压为40V时,喷头变幅杆端面的平均振幅为3.30μm,悬浮球振幅为0.283mm;当电压增加到46V时,喷头变幅杆端面的平均振幅达到3.96μm,悬浮球振幅增加到0.301mm。由测试结果得出,喷头样机的工作性能满足设计要求,且变幅杆端面振幅和悬浮球振幅正相关于驱动电压。为了了解喷头的实际工作性能,利用所设计的喷头样机完成了喷雾试验。采用高清相机对喷头喷雾角进行了测试,通过对比试验可以发现:在没有采用涡流齿轮的情况下,喷头喷雾角与气压呈现正相关关系;对于采用涡流齿轮的超声雾化喷头,当气流压力较小时,涡流齿轮对喷雾角的影响很小;当气压增加达到0.1MPa时,带有涡流齿轮的喷头喷雾角为36°,而不带涡流齿轮的喷头喷雾角仅为19°;当气压达到0.4MPa时,涡流齿轮帮助喷头达到了平均66°的喷雾角,与不带有涡流齿轮的喷头相比,喷雾角的增加幅度达到60.9%,体现出涡流齿轮在增大喷雾角方面的重要作用。采用激光粒度分析仪对喷头的雾滴粒径进行了试验研究,分析并比较了不同喷口收角、气压大小及悬浮球对于雾滴粒径的影响。由试验结果发现:(1)驱动电压对于60KHz超声雾化喷头的雾化效果具有一定的影响,40V的驱动电压所产生的雾滴粒径大于46V驱动电压下产生的雾滴粒径。(2)喷口收角对雾滴粒径没有明显的影响。(3)气流能够明显地影响到喷头所产生雾滴的平均粒径及粒径分布宽度。当气压为0.05MPa时,喷头产生的雾滴平均粒径减小超过10%,粒径分布宽度也同时减小;而当气压达到0.1MPa时,雾滴平均粒径减小得不明显,甚至有可能增大,但粒径分布宽度进一步缩小。(4)带有悬浮球的超声喷头所产生的雾滴粒径要远小于没有悬浮球的喷头,且悬浮球能够比气流更明显地减小雾滴尺寸。如何更好地将辅助气流与悬浮球这两种手段相结合,对于提高喷头的雾化质量具有重要意义。
[Abstract]:Ultrasonic atomizer can produce smaller droplets than ordinary pressure sprinklers, which make it meet the needs of crop growth and achieve the purpose of saving water resources and reducing the use of pesticides. For the liquid with large viscosity, such as pesticide or nutrient solution, the ultrasonic atomizer can be more easily atomized, so it is in agriculture. In order to solve the existing technical problems, in order to solve the existing technical problems, further refine the droplet size and improve the uniformity of the spray, increase the spray angle and enhance the anti interference ability of the spray, this paper sets up a gas assisted low frequency ultrasonic atomizer with the method of computer modeling and finite element analysis, and is based on this basis. The design scheme of the swirl gear and the two atomization design with a metal suspension ball are developed. The basic structure of the nozzle includes the mechanical vibration structure and the fluid structure. The design of the nozzle is verified by the method of combining the computer software modeling with the finite element simulation. The mechanical vibration structure of the nozzle includes the structure of the nozzle. Two parts of ultrasonic transducer and ultrasonic horn are calculated by theoretical calculation, and the corresponding mathematical calculation process and calculation result are given. The CAE method of modal analysis and harmonic response analysis is used to simulate the structure of the design, and the simulation results are compared with the theoretical design values. In order to determine the final parameters of the various parts of the structure, the fluid structure of the nozzle is designed and analyzed by the method of fluid simulation. The feasibility of the structure design is verified by observing the movement of the air flow inside the nozzle and the jet situation at the nozzle. The specific characteristics of the machine are tested. The impedance characteristics of the prototype of the nozzle are analyzed, the resonance frequency of the prototype is 57984Hz, and the difference between the theoretical design frequency 60KHz of the nozzle is 3.4%, and the other key parameters of the nozzle transducer are obtained, which provide the design basis for the design of the driving power of the nozzle. The amplitude of the floating ball is measured. When the voltage of the power supply is 40V, the average amplitude of the end face of the nozzle is 3.30 mu m and the amplitude of the suspension ball is 0.283mm. When the voltage is increased to 46V, the average amplitude of the end face of the nozzle is 3.96 M, and the amplitude of the suspension ball is increased to 0.301mm. by the test result, and the working performance of the prototype of the nozzle is satisfied. In order to understand the actual working performance of the nozzle, the spray test is completed by using the prototype of the designed nozzle. The spray angle of the nozzle is tested with a high definition camera, and the spray head can be found in the case of no swirl gear. There is a positive correlation between the spray angle and the air pressure; for the ultrasonic atomizing nozzle with swirl gear, the effect of the swirl gear on the spray angle is small when the air pressure is small. When the pressure increases to 0.1MPa, the spray angle of the nozzle with the swirl gear is 36 degrees, and the spray angle of the nozzle without the swirl gear is only 19 degrees; when the pressure reaches 0.4MPa When the swirl gear helps the nozzle to reach the spray angle of an average of 66 degrees, the increase of the spray angle is 60.9%, compared with the nozzle without the swirl gear, which reflects the important role of the swirl gear in increasing the spray angle. The particle size of the spray head is studied by the laser particle size analyzer, and the different spray is analyzed and compared. The effect of mouth angle, pressure size and suspension ball on droplet size is found. The results are as follows: (1) the driving voltage has a certain influence on the atomization effect of 60KHz ultrasonic atomizing nozzle. The droplet diameter produced by the driving voltage of 40V is larger than that of the 46V driving voltage. (2) the nozzle angle is not obvious to the droplet size. (3) the air flow can obviously affect the average particle size and the size distribution width of the droplets produced by the spray head. When the pressure is 0.05MPa, the average particle size of the spray droplets is reduced by more than 10%, and the size distribution width decreases at the same time. When the pressure reaches 0.1MPa, the average particle size of the droplet decreases not obviously, even if it is likely to increase, but the grain size is even larger. The diameter distribution width is further reduced. (4) the droplet diameter produced by the ultrasonic sprinkler with the suspension ball is much smaller than that without the suspended ball, and the suspension ball can reduce the droplet size more obviously than the air flow. How to better combine the auxiliary air and the suspended ball are important to improve the atomization quality of the nozzle. Righteousness.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S237;TH122

【参考文献】