Introduction to the principle of ultrasonic atomization

Update time:27-02-2020

A piezoelectric ceramic sheet (commonly known as an ult […]

A piezoelectric ceramic sheet (commonly known as an ultrasonic atomizing sheet) is installed on the bottom of a water container, and a driving control circuit generates a driving voltage that is consistent with the resonant frequency of the atomizing sheet and adds the driving voltage to the atomizing sheet. Oscillating energy. The oscillating energy propagates in the water in a direction perpendicular to the surface of the atomizing sheet. Under a suitable water depth, the water surface on the energy propagation axis concentrates a ridge of water, and the front end of the water column generates a large number of small tension waves, which cause the water surface to bulge. The surface tension of water is greatly reduced. The surface of the water is split into many small areas by the wavelength of the surface tension wave. Each area seems to be independent of each other as particles, which are dispersed in the air to form a fog effect. This is The principle of ultrasonic atomization.



Ultrasonic atomization is a process that uses ultrasonic energy to form liquid into fine mist droplets.


Ultrasonic can atomize liquid in two ways:

1. The thin liquid layer on the vibrating surface excites capillary-gravitational waves under ultrasonic vibration.


2. The atomization method is the ultrasonic fountain fogging.

method one


There are two theoretical explanations for the principle of ultrasonic atomization. They are the micro shock theory and the surface tension wave theory.


On the one hand, the microshock theory explains that the cavitation effect of ultrasonic waves in a liquid medium leads to the generation of microshock waves and thus atomization. This theory believes that the cavitation effect is the direct cause of the atomization of the liquid. When the cavitation bubble collapses, in addition to generating heat and light radiation, the rest is radiated in the form of microshock waves. When the microshock waves reach a certain intensity, the liquid is caused. Atomization causes the atomization of the liquid when the micro shock wave reaches a certain intensity.


On the other hand, surface tension theory believes that the generation of mist droplets is caused by the instability of liquid surface waves, which causes the liquid to atomize. Specifically, when a certain sound intensity ultrasonic wave passes through the liquid and points to the gas-liquid interface, the ultrasonic waves form surface tension waves at this interface. Under the force perpendicular to the surface tension wave, once the amplitude of the vibration surface reaches a certain value, the droplets fly out from the wave peak and form atomization. According to this theory, the surface tension wave generates droplets at its peak, and the droplet size is proportional to the wavelength. Surface tension wave model and surface tension wave atomization model diagram.


Way two

Fountain atomization, which is a common form of ultrasonic atomization, uses a piezoelectric chip as a transducer to generate megahertz-level ultrasonic waves. Generally, the formation mechanism of fountain atomization is as follows. When the ultrasonic transducer emits ultrasonic waves at the megahertz level, the directivity of the ultrasonic wave and its cavitation field is very good, so the solution in contact with it will be sprayed up to form an "ultrasonic fountain." .


Radon is accompanied by a large amount of aerosols when the ultrasonic fountain is produced. Among them, the "ultrasonic fountain" can be regarded as an upward spraying ultrasonic cavitation field, which has a unidirectional radiating force and a symmetrical swirling sound stream. In this cavitation field, the distribution of cavitation bubbles is very different. During the cavitation of liquids such as water, due to the effect of acoustic radiation pressure, due to the density of cavitation bubbles and the physical effects of ultrasonic radiation and beam spraying, the concentrated thermal and mechanical effects of a large number of cavitation bubbles are more prominent at the front of the fountain The sound energy density is also greatly increased along the spray direction due to the ultrasonic free jet and beam jet.


In the ultrasonic fountain, the large-scale cavitation bubble collapse, burst high-temperature acoustic rush and high pressure shock wave are the main mechanisms of the ultrasonic fountain. Other mechanical agitation, thermal effects, etc. also exist. Ultrasonic humidifiers designed using this principle are often used as indoor humidifiers. It can humidify and remove static electricity from equipment in computer rooms and wool spinning workshops; add drugs for indoor sterilization and disinfection, perform facial beauty, and shape bonsai.