Design And Spray Test Of Air-asistant Low-frequency Ultrasonic Nozzle

Compared with the ordinary pressure nozzle,the ultrasonic atomization nozzle can produce smaller droplets,making it able to meet the growth needs of crops,while achieving the purpose of water conservation and reducing the use of pesticides.Ultrasonic atomization nozzles can more easily atomize pesticides or nutrient solution and other viscous liquid,so it has a unique advantage in the field of agricultural fertilization.In order to solve the existing technical problems,further refine the droplet size and improve the uniformity of the spray,increase the spray angle of the nozzle,enhance the anti-jamming effect of the spray,the method of computer modeling and finite element analysis was used to design the air-assisted lowfrequency ultrasonic atomization nozzle in this paper.And on this basis,nozzle with vortex gear and nozzle with metal levitation ball for a second atomization were designed.The basic structure of the nozzle includes mechanical vibration structure and fluid structure.The design of the nozzle was verified by the combination of computer software modeling and finite element simulation.The mechanical vibration structure of the nozzle includes two parts: ultrasonic transducer and ultrasonic horn.The concrete numerical calculation of each dimension in the structure is obtained by theoretical calculation,and the corresponding mathematical calculation process and calculation result are given.The structure of the design was simulated by CAE method such as modal analysis and harmonic response analysis.The simulation results were compared with the theoretical design results to verify the design scheme,so as to determine the final parameters of each part of the structure.The fluid structure of the nozzle was designed and analyzed by the method of fluid simulation.The rationality of the structural design was verified by observing the movement of the internal fluid in the nozzle and the jet out of spout.A nozzle prototype was manufactured according to the design parameters,and the specific characteristics of the prototype were tested.The impedance characteristics of the nozzle prototype were analyzed,and the resonant frequency of the nozzle prototype was 57984 Hz,which was 3.4% lower than the theoretical design frequency;other key parameters of the nozzle transducer were obtained.These parameters provided the design basis for the design of the nozzle drive power supply.The amplitude of the end face of the nozzle and the amplitude of the suspended ball were measured.When the power supply voltage is 40 V,the average amplitude of the nozzle end is 3.30?m and the amplitude of the suspended ball is 0.283 mm.When the voltage increases to 46 V,the average amplitude of the head of the nozzle is 3.96?m,and the amplitude of the suspended ball is increased to 0.301 mm.From the test results,it can be concluded that the working performance of the nozzle prototype meet the design requirements,and the amplitude of the amplitude of the horn and the amplitude of the levitation ball are related to the drive voltage.In order to confirm the actual performance of the nozzle,the nozzle prototype was used to complete the spray test.The HD camera was used to test the nozzle spray angle.Through the comparative test,it can be found that: in the absence of the use of vortex gear,spray angle and pressure show a positive correlation;for the ultrasonic atomization nozzle with vortex gear,when the air pressure is low,the vortex gear has small impact on the spray angle;when the air pressure increases to 0.1MPa,nozzle with vortex gear has spray angle of 36 °,while the spray angle of nozzle without vortex gear is only 19 °;when the air pressure to 0.4MPa,the vortex gear help the nozzle reached an average of 66 ° spray angle,and the spray angle increases by 60.9% compared to nozzle without vortex gear.This reflects that vortex gear play an import role in increasing the spray angle.The droplets size of the nozzle was studied by laser particle size analyzer.The effects of different nozzle angle,air pressure and suspended ball on the droplets size were analyzed and compared.The conclusions are as follows:(1)The driving voltage has a certain effect on the atomization effect of the nozzle of 60 KHz.The droplets size of the driving voltage of 40 V is less than the droplets size of the 46 V driving voltage.(2)The nozzle angle has no significant effect on the droplets size.(3)The airflow can significantly affect the average particle size and the distribution of the droplets size.When the air pressure is 0.05 MPa,the droplets produced by the nozzle decreases by more than 10% and the particle distribution width decreases as well;when the air pressure reaches 0.1MPa,the decrease of the average droplets size is not obvious,and may even increase,but the particle size distribution width is further reduced.(4)The droplets size of the nozzle with levitation ball is much smaller than that of the nozzle without the levitation ball,and the levitation ball can reduce the droplet size more significantly than the airflow.It is significant to combine the auxiliary airflow and the suspended ball to improve the atomization quality of the nozzle.