Numerical Simulation On Atomization Characteristics Of Ultrasonic Vibration Nozzle

The increase of dust concentration in industrial production poses a great hidden danger to production safety,and the small particle size of respiratory dust in dust causes pneumoconiosis in workers.At present,mainly adopts the wet-type dust-falling of the water medium spray,and for the respiratory dust in the dust,the atomization diameter of the common nozzle is relatively large,and the atomization effect is not ideal.Hartmann whistle ultrasonic atomizing nozzle as a fluid powered nozzle.It can generate ultrasonic using its own structure.The droplet size can reach about 10 micrometers,which can effectively make respiratory dust settle.In this paper,the analysis of previous for Hartmann whistle sound mechanism and ultrasonic atomization mechanism and the advantages of the self-excited oscillating nozzle and the bubble atomizing nozzle are proposed to design an ultrasonic vibration nozzle.The structural parameters such as the resonant cavity and the collision wall and the gas-liquid two-phase mixing are analyzed.After the impact on the internal flow field of the ultrasonic excitation nozzle,the relationship between the resonant cavity structure and the sound pressure is analyzed and calculated.Fluid dynamics software FLUENT was used to simulate the internal flow field of the ultrasonically excited nozzle under liquid working conditions.The simulation mainly analyzed the internal flow of the nozzle under different structural parameters(collision wall angle,resonant cavity diameter,resonant cavity depth,resonance distance).The effect of the field and fluid pouring into and out of the resonant cavity is further analyzed to produce the relationship between ultrasonic intensity and infusion effect.The results show that the velocity distribution and pressure distribution in the flow field are all layered,and there are vortices generated.According to the effect of the fluid poured into and out of the resonant cavity,the design parameters of the structural parameters are obtained:a = 60°-70°、l= 3-4 mm、d= 4-6mm、L = 5-7 mm,provide reference for later research.The acoustical characteristics of the resonant cavity of the key structure of the ultrasonic excitation nozzle are simulated by the acoustic module in the FLUENT software.The simulation mainly analyzes the effects of different structural parameters of the resonator(resonant cavity diameter,resonant cavity depth,resonance distance)on the sound pressure of the ultrasonic excitation nozzle.,And the resonator filling and punching effect and the sound pressure contact,verify the nozzle structure parameters,according to the sound pressure and fluid filling into the situation,It is concluded that the sound pressure of the resonator is the structural parameter of the resonator when the effect of the fluid is goodThe VOF model in the FLUENT software is used to simulate the flow field of the nozzle and the same axis into the nozzle.The simulation mainly analyzes the movement of the gas in the nozzle and the distribution and velocity of the gas at different inlet pressures and gas volume fractions.The simulation results show that the gas phase and the liquid into the nozzle after the same axis into the nozzle.Because the two working substances are incompatible and have different viscosities,velocity difference will occur.The gas phase working medium will continuously gather together in the vicinity of the tube wall and the symmetry axis to form bubbles,and finally into nozzle lumen.when the pressure is constant,the greater the inlet gas content,the easier the gas phase in the nozzle to gather into the bubbles,and the larger the bubble volume in the cavity,the same time the fluid velocity in the nozzle increases;when the inlet gas content is constant When the pressure is higher,the bubbles are easier to collect but the gas content in the nozzle cavity does not change much.The higher the inlet pressure,the greater the fluid velocity in the nozzle.According to the analysis,the imported gas content is 20%30%,and the inlet pressure is 4-5MPa The inlet pressure of 4～5MPa nozzle cavity more fluid,the greater the turbulence disturbance for the liquid in the nozzle cavity.