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The phenomenon of ultrasonic atomization originates from the acoustics and physics of the late 19th century. Simply put, when a liquid film is placed on a smooth surface that vibrates in a direction perpendicular to the surface, the liquid absorbs the vibrational energy. This energy converts into standing waves known as capillary waves. As the amplitude of the vibration increases, the amplitude of the waves correspondingly rises. Once the critical amplitude is reached, the height of the capillary waves exceeds the threshold needed for stability. At this point, the waves collapse, and tiny droplets are ejected from the peaks of the degraded waves perpendicular to the atomizing surface.
Figure 1. The working status of ultrasonic spray nozzle
The ultrasonic spray nozzle atomizes liquid using high-frequency sound waves beyond the range of human hearing. The ultrasonic generator converts a 50/60Hz voltage into high-frequency electrical energy, transmitting it to the piezoelectric transducer inside the nozzle, where it transforms into mechanical vibrations. The ultrasonic vibrations are amplified and focused at the nozzle tip, where atomization occurs. Each ultrasonic spray nozzle operates at a specific frequency, and the droplet size produced varies with frequency. The operating frequency of the ultrasonic spray nozzle is typically selected based on different application scenarios. Additionally, the amplitude of the ultrasonic spray nozzle plays a critical role in ultrasonic atomization. To achieve optimal atomization, the vibration amplitude of the atomizing surface must be carefully controlled. At the critical amplitude, the energy is insufficient to atomize the liquid; however, if the amplitude is too high, the liquid may tear and eject large fluid masses, a phenomenon known as cavitation. Thus, precise control of ultrasonic atomization power is crucial for achieving ideal atomization.
The ultrasonic spray nozzle distinguishes itself from other atomizing nozzles with its gentle, low-flow, precisely controlled, and pressure-free atomization. These features offer outstanding advantages in various coating applications. Under pressure-free atomization, droplets tend to deposit on the substrate rather than rebound, thus avoiding overspray. This not only conserves material but also reduces environmental emissions.
Figure 2. Siansonic all series ultrasonic spray nozzles.
The ultrasonic spray nozzle allows for precise spray control and shaping. With the assistance of airflow, it achieves a spray width ranging from a few millimeters to several dozen millimeters. Furthermore, since ultrasonic atomization by the ultrasonic spray nozzle does not rely on pressure, the amount of liquid atomized per unit time is entirely controlled by the liquid supply system. Flow rates as low as a few microliters per minute can be achieved, enabling highly precise spray control. Droplets produced by ultrasonic atomization have a narrow size distribution, meaning more uniform particle sizes. This feature demonstrates significant advantages in both coating applications and pyrolytic granulation.
Siansonic Technology Limited, based in Beijing, brings nearly 40 years of technical expertise in the ultrasonic field, providing ultrasonic spray nozzles and related products for ultrasonic spray coating technology to enterprises worldwide.
