Introduction To The Principle Of Ultrasonic Atomization

Introduction To The Principle Of Ultrasonic Atomization

Date:Dec 09, 2020

Ultrasonic atomization is the process of using ultrasonic energy to make liquid form fine droplets.

There are two ways to atomize liquid by ultrasonic wave:

   1. The thin liquid layer on the vibrating surface excites a capillary-gravity wave under ultrasonic vibration.

   2. The atomization method is the ultrasonic fountain to form fog.

Method one

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

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

On the other hand, the surface tension theory believes that the generation of mist droplets is due to the instability of the liquid surface wave, which causes the liquid to atomize. Specifically, when a certain sound intensity of ultrasonic waves is directed to the gas-liquid interface through the liquid, the ultrasonic waves form surface tension waves at this interface Once the amplitude of the vibrating surface reaches a certain value under the action of the force perpendicular to the surface tension wave, the liquid droplets fly out of the wave crest to form atomization. This theory believes that the surface tension wave produces droplets at its peak, and the droplet size is proportional to the wavelength. The surface tension wave model and the surface tension wave atomization model diagram.

Method Two

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

A large amount of aerosol is also produced when the ultrasonic fountain is produced. Among them, the "ultrasonic fountain" can be regarded as an upward jetting ultrasonic cavitation field, which has a unidirectional radiation force and a symmetrical whirling sound flow. In this cavitation field, the distribution of cavitation bubbles is very different. When water and other liquids are cavitation, due to the effect of acoustic radiation pressure, the density of cavitation bubbles due to the physical effect of ultrasonic radiation force and bunching jet, the concentrated heat 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 improved along the jetting direction due to ultrasonic free jet and bunch jet.

In the ultrasonic fountain, the high-temperature acoustic rush and high-pressure shock waves when a large number of cavitation bubbles collapse and burst are the main mechanisms of the ultrasonic fountain. Other mechanical stirring effects, thermal effects, etc. also exist at the same time. Ultrasonic humidifiers designed using this principle are often used as indoor humidification devices. It can humidify computer rooms and wool spinning workshops to remove static electricity from equipment; add drugs for indoor sterilization and disinfection, facial beauty, and bonsai modeling, etc.

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