MIE.30 – Variable Orifice Nozzle Project for Spraying Systems Co.

• Hannan Ahmad
• Matthew Atchison
• Andres Aviles
• Raunak Chakrabarty

The goal of this project was initially to create a variable orifice nozzle using active materials for our sponsor, Spraying Systems. A variable orifice nozzle offers many advantages as compared to a fixed orifice nozzle. Being able to change the exit area allows for the flow and spray pattern to be controlled, as opposed to having a fixed exit area. The initial idea was to use active materials to vary the exit size. Active materials are materials that respond input stimuli; for example, a dielectric elastomer, which is a type of active material, changes size in response to a voltage input. Using this sort of material in place of a mechanical system for varying exit size would save on weight, bulkiness, and complexity. After some time and research, it was concluded that procuring and active material and incorporating it into a design was outside of the scope of the project given the timeline, as active materials are still an area that is being researched heavily; materials for production scale manufacturing are prohibitively expensive.
Because of these issues with active materials, the team had to pivot to a new type of design, that instead used pressurized air to constrict a rubber membrane. This design ended up being refined through several versions, the culmination of which was a prototype. Inside of the nozzle is a chamber, which can be pressurized externally, using a compressor, or in this case, a bicycle pump. The hollow elastic cylinder inside of the nozzle is exposed to this pressure on its outer surface, while the fluid flow passes through the center. The difference in pressures between the pressure chamber and fluid stream causes a force that constricts the elastic material, reducing the area through which the fluid flows. This can change in area is used to change the nozzle’s spray characteristics.
The prototype created was evaluated using a variety of material types for the elastic membrane. Standard sized tubes were used, with different durometers and varying elasticity. A Schrader valve was connected to the pressure chamber, allowing for a bicycle pump to be used to create pressure, and thus change the exit area of the nozzle. Water was flown through the nozzle, and the change in spray characteristics were observed with different pressure and different membrane materials.