Nozzle diameter and expansion ratio of compressed air foam system

Abstract

Variations of nozzles are studied for Compressed Air Foam Systems (CAFS). The CAFS is a self-contained fire suppression system with the capability of injecting compressed air into the foam solution to create a dense mist. Even though this type of foam has a tighter, denser bubble structure that allows it to adhere to vertical and horizontal surfaces and penetrate the fire more deeply before the bubbles burst, thereby making it more effective, the nozzle of CAFS is weak. The experimental study has been done in order to find the expansion ratio of the nozzle. Four sizes of diameter nozzles are 5 mm, 10 mm, and 20 mm, and three holes are 20 mm. Nozzle diameter size has a correlation with bubble size. The highest expansion ratio is found in the nozzle with three holes 20 mm in diameter. It is followed by a nozzle with a 20 mm diameter, then a 10 mm diameter. The last finding is a nozzle with five diameters. The other founding is the linear correlation between nozzle diameter size and bubble size. But it is on the other way than the correlation between nozzle diameter and bubble size. The shorter the nozzle diameter, the faster the fire extinguishing time.