The history of ultrasonic cleaners

Ultrasonic cavitation refers to the dynamic process of growth and collapse that occurs when the sound pressure reaches a certain value, which is caused by the micro-nuclear cavitation bubbles present in the liquid. Cavitation generally consists of three stages: the formation of cavitation bubbles, growth and severe collapse. When a container filled with liquid is subjected to ultrasonic waves, tens of thousands of tiny bubbles, that is, cavitation bubbles, are generated due to the vibration of the liquid. These bubbles grow in the negative pressure region formed by the longitudinal propagation of the ultrasonic waves, and are rapidly closed in the positive pressure region, thereby being compressed and stretched under alternating positive and negative pressures. At the moment when the bubble is compressed until it collapses, there is a huge transient pressure, typically up to tens of megapascals to hundreds of megapascals. Suslick et al. measured that cavitation can bring the temperature in the gas phase reaction zone to about 5 200 K, the effective temperature in the liquid phase reaction zone to about 1 900 K, and the partial pressure at 5. O5 × 10 kPa, the temperature change rate is as high as 10. K/s with a strong shock wave and a microjet with a speed of 400 km/h. This huge instantaneous pressure can cause a sharp damage to the surface of the solid suspended in the liquid. Ultrasonic cavitation is usually divided into two types: steady cavitation and instantaneous cavitation: steady cavitation is the cavitation bubble generated when the sound intensity is low (generally less than 10 w/cm), and its size is balanced. Oscillation near the size, the generation cycle is several cycles. When expanded to make its own resonant frequency equal to the acoustic wave frequency, the maximum energy coupling between the sound field and the bubble occurs, resulting in significant cavitation. Transient cavitation refers to cavitation bubbles with a short life cycle (mostly occurring in one sonic cycle) produced by a large sound intensity (generally greater than 1 O w/cm).

First, the ultrasonic cleaning work is done by cavitation bubbles located on or near the surface of the cleaning workpiece. The ultrasonic cavitation mainly shows the following aspects:

(1) The microbubbles present in the liquid vibrate under the action of the sound field. When the sound pressure reaches a certain value, the bubbles will rapidly become large and then close quickly. When the bubble is closed, the shock wave can generate thousands of atmospheres around it. The pressure destroys the insoluble dirt and disperses them in the cleaning solution.

(2) The direct repeated impact of the vapor-type cavitation on the dirt layer, on the one hand, destroys the adsorption of the dirt and the surface of the cleaning member, and on the other hand, causes the fatigue damage of the dirt layer to be detached from the surface of the cleaning member.

(3) The vibration of the gas-type bubble scrubs the solid surface. Once the dirt is sewed, the bubble can be “drilled” into the crack to vibrate, causing the stain to fall off.

(4) For solid particles wrapped with oil, due to the effect of ultrasonic cavitation, the two liquids are quickly separated at the interface and emulsified, and the solid particles fall off.

(5) Ultrasonic cavitation The high-speed micro-jet generated at the interface between solid and liquid can remove or cut off the boundary layer, increase the stirring effect, accelerate the dissolution of soluble dirt, and strengthen the cleaning effect of chemical cleaning.

Second, the characteristics of ultrasonic cleaning:

(1) Ultrasonic cleaning is characterized by high speed, high quality and easy automation. It is especially used for workpieces with complex surface shapes. For holes, slits, grooves, micropores, dark holes, etc. on precision workpieces, the usual scrubbing method is difficult to achieve, and ultrasonic cleaning can achieve good results.

(2) Another feature of ultrasonic cleaning is that it has a good cleaning effect on materials with hard texture and strong sound reflection (such as metal, glass, ceramics, plastic).

(3) Good cleaning effect, high cleanliness and consistent cleanliness of all workpieces.

(4) The cleaning speed is fast, the production efficiency is improved, and the cleaning liquid is not required to be touched by human hands, which is safe and reliable.

(5) The deep holes, slits and hidden parts of the workpiece can also be cleaned.

(6) No damage to the surface of the workpiece, saving solvent, heat, work site and labor.

The wide application of ultrasonic waves in various fields is the application of its cavitation and its cavitation accompanied by mechanical effects, thermal effects, chemical effects, biological effects, etc., mechanical and chemical effects, the former mainly in heterogeneous reactions The increase of the interface; the latter is mainly due to the high temperature and high pressure generated during the cavitation process, such as polymer decomposition, chemical bond cleavage and generation of free radicals. The processes utilizing mechanical effects include adsorption, crystallization, electrochemistry, heterogeneous chemical reactions, filtration, and ultrasonic cleaning. The processes utilizing chemical effects mainly include organic matter degradation, polymer chemical reactions, and other free radical reactions.