Relevant studies believe that ultrasonic atomization is the process of using ultrasonic energy to make the liquid form fine droplets in the gas phase, that is, ultrasonic waves are generated on the vibrating liquid surface, and the vibration peak composed of amplitude separates and breaks the droplets from the surface. With the increase of ultrasonic frequency, atomized droplets become finer and finer. Generally, fine droplets can be obtained under the action of ultrasonic vibration frequency. In addition, the ultrasonic frequency field can also eliminate or thin the temperature boundary layer near the heat transfer surface, so as to promote heat transfer.
Ultrasonic atomizing nozzle
Ultrasonic atomizers are divided into two categories: hydrodynamic type and electroacoustic energy conversion type. Hydrodynamic ultrasonic atomization uses high-speed gas or liquid to excite the resonant cavity to produce ultrasound. Its frequency is mainly determined by the geometric size of the resonant cavity. The droplet size is related to the liquid flow rate, air pressure and nozzle structure. Ultrasonic atomization technology adopts hydrodynamic ultrasonic atomizer. In addition, ultrasonic atomization of external water, organic liquid, molten metal and other liquid media often adopts this form.
Electroacoustic transducer ultrasonic atomization uses the transducer to convert the high-frequency electromagnetic oscillation into the mechanical oscillation of the liquid, so that the liquid is broken into fog. There are two main forms: one is that the piezoelectric transducer radiates strong ultrasound in the liquid, radiates into the liquid through the thin sound permeable film, and produces fountain atomization on the liquid surface, which is the typical principle of ultrasonic humidifier; The other is that the liquid flows to the surface of the ultrasonic concentrator and forms a thin liquid layer. The thin liquid layer excites the surface tension wave under the action of ultrasonic vibration. When the amplitude of the vibration surface reaches a certain value, the droplets fly out of the wave crest to form atomization.
Atomizing nozzle is a device in the atomization device that enables the atomizing medium to obtain high energy and high speed. It is also a key component that plays an important role in the atomization efficiency and the stability of the atomization process. Its function is to control the flow and flow pattern of atomizing medium in order to effectively break liquid metal and produce powder with specific properties. In fact, the atomizer is a transducer, which converts the kinetic energy of high-pressure gas into the surface energy of metal. As a transducer, its energy conversion efficiency is very important.
