Current aircraft fire suppression bottles for dry bay and engine nacelle applications, which are designed to meet Military Specification MIL-C-22284A (proof pressure of 9.62 MPa and minimum burst pressure of 12.37 MPa), are normally filled with liquid halon 1301 (CF3Br) to about half of the bottle volume, and the bottle is then pressurized with nitrogen to a specified equilibrium pressure (typically 4.1 MPa) at room temperature. The purpose of using the pressurization gas is to expedite the discharge of the agent and to facilitate the dispersion of the agent. Without nitrogen pressurization, the bottle pressure, which is simply the vapor pressure of the agent, can be so low (even sub-atmospheric) at extremely cold ambience that there is virtually no driving force to expel the agent from the bottle in case of a fire, thus hindering a rapid release of the mixture. From the above description, three important issues have emerged and need be considered when using a halon alternative as an in-flight fire suppressant: (1) the system hardware, (2) the thermophysical properties of the agent/nitrogen mixture, and (3) the agent/nitrogen mixture behavior during a discharge. The results obtained from this study provide important technical information on bottle design and agent discharge for new generation aircraft that may use the halon alternatives, for the existing aircraft that may undergo retrofitting, or simply for possible "drop-in" replacements.
Citation: Special Publication (NIST SP) - 890
NIST Pub Series: Special Publication (NIST SP)
Pub Type: NIST Pubs
fire suppression, aircraft engines, nacelle fires, simulation, thermophysical properties, nitrogen, discharge rate, computer simulation, halon 1301, halon alternatives