There are two types of ultrasonic atomizers: one is an electroacoustic conversion type ultrasonic atomizer; the other is a fluid dynamic type ultrasonic atomizer. Among them, the electroacoustic conversion type converts an electric signal into mechanical vibration, and then generates ultrasonic waves by mechanical vibration. When the ultrasonic wave propagates from the bottom to the liquid surface, a mist will appear on the liquid surface, thereby effecting atomization. The shade of the mist is related to the intensity of the ultrasonic waves, and the size of the droplets is related to the frequency of the ultrasonic waves and the surface tension of the liquid. According to the operating frequency of the ultrasonic atomizer, it can be divided into various application devices such as low frequency and high frequency. Generally, the frequency range of high-frequency ultrasonic atomization is between 0.8 and 5 MHz for medical treatment, humidification and the like.
Generally, ultrasonic atomizers or aromatherapy machines that can be seen on the market use an oscillation frequency of 1.7M or 2.4M. This frequency is a more mature frequency. It is widely used because of its high conversion efficiency and moderate particle size of water mist.
In the production process of low-power ultrasonic atomizer (5W-25W), we found that there are several major factors that affect the atomization effect of the ultrasonic atomizer and the stability of the atomization amount.
1. The consistency of the atomized sheet and the degree of attenuation of the atomized sheet
The atomizers commonly used in the market usually use 1.7M or 2.4M ultrasonic ceramic oscillators. Due to the introduction of some uncertain factors in the batching and production process of the production of the atomized sheet, the consistency of the atomized sheet is poor. Generally, the fogging efficiency of the atomized sheet will vary by ±20%.
After a long period of work or due to the influence of water quality, the atomized film will have a programmed decay. As a result, the amount of atomization is reduced, or fogging or even complete damage occurs. Therefore, the degree of attenuation of the atomized sheet is an important indicator for evaluating the quality of the atomized sheet.
2. The influence of water level
We all know that ultrasonic waves are attenuated in water. The nebulizer output is generally constant power. When the water level of the atomizer is different, the power of the ultrasonic wave emitted by the atomizing sheet to the water surface is also different, thereby affecting the atomization effect. So when designing the atomizer, the water level is a very important factor. When the water level is high, the atomizer will be difficult to fog, or the amount of atomization will be small. Of course, the lower the water level, the larger the atomization amount. When the water level is too low, the complete liquid level cannot be formed (the atomizer effect is affected by the surface tension of the liquid) and the fog cannot be generated from the surface.
3. Influence of ultrasonic installation direction
Ultrasonic extended linear propagation. Therefore, the ultrasonic wave emitted from the atomizing sheet propagates in the direction perpendicular to the atomizing sheet, and the direction of the water column ejected from the atomizer can also be verified. According to the theory of surface tension, the generation of droplets is caused by the instability of the surface wave of the liquid, which causes atomization of the liquid. Specifically, when a certain intensity of ultrasonic waves is directed to the gas-liquid interface through the liquid, the ultrasonic waves form a surface tension wave at the interface. When the amplitude of the vibration surface reaches a certain value due to the vertical force of the surface tension wave, the droplets fly out from the peak to form atomization. Therefore, keeping the direction of ultrasonic wave propagation perpendicular to the liquid surface can better exert the atomization efficiency of the atomized sheet. Nowadays, there are many atomizer atomizers on the market that are installed at an angle to the horizontal plane. This type of installation will affect the fogging effect of the atomizer. Especially when the water level of the atomizer is low, the atomizer will not be able to fog, and the energy of the atomizer is converted into heat energy in a large amount, so that the water temperature rises remarkably, and the life of the atomizer is greatly affected.