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PrintHow Ultrasonic Nozzles Work
Every ultrasonic nozzle operates at a specific resonant frequency, which is determined primarily by the length of the nozzle.
A cross-sectional view of a typical production nozzle is shown below. There are several features worth noting.
The electrically active elements are contained within a sealed housing that protects the lead zirconate/titanate piezoelectric transducers, electrodes, and connecting wires from external contamination. Chemically impervious o-rings assure the integrity of the seal.
The housing provides a convenient location for mounting the nozzle in most applications since it is the only portion of the nozzle that is not ultrasonically active. For applications involving an interface to a vacuum chamber or another type of chemical reaction chamber, the housing can be fitted with or made an integral part of a mounting flange that bolts to an existing port on the reactor.
Both the front and rear horns are fabricated from a very high-strength titanium alloy (Ti-6Al-4V). This alloy also exhibits exceptional resistance to chemical attack. The housing is fabricated from 316 stainless steel. The electrical connector is a hermetically sealed SMA connector fabricated from stainless steel. The o-ring seals between the titanium horns and the front and rear portions of the housing are Kalrez (trademark of Dupont). The o-ring seal between the front and rear housings is Viton (trademark of Dupont).
The liquid feed tube that runs the entire length of the nozzle is an integral part of the front titanium horn. Thus, the liquid only comes into contact with titanium within the nozzle. Typically, the nozzle is supplied with a 316 stainless steel compression fitting mounted on the rear of the liquid feed tube, which is mated to appropriate polymeric tubing.
The nozzle shown above features a cone-shaped atomizing surface. Its purpose is to spread out the spray. Some applications require that the spray be very narrow. In those cases, the atomizing surface is sculptured into a flat or nearly-flat surface. Depending on the width requirements of the spray pattern and the required flow rate, the atomizing surface may have a very small diameter or an extended, flat section. The possibilities are shown below.
The illustration on the left in the diagram to the right indicates a cone-shaped spray pattern resulting from the conically shaped atomizing surface. Typically, spray envelope diameters from 2-3 inches can be achieved.
The center illustration is characteristic of Sono-Tek MicroSpray™ nozzles. For this type of nozzle, the orifice size ranges from 0.015-0.040 inches. It is usually recommended for use in applications where flow rates are very low and narrow spray patterns are needed.
The illustration on the right depicts a cylindrical spray shape used in applications where the flow rate can be relatively high, but where the lateral extent of the spray pattern must be limited.
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