Integrated Aircraft Fuel Tank Inerting and Compartment Fire Suppression System. Volume 2. Evaluation of Nitrogen-Enriched Air as a Fire Suppressant

摘要

Aircraft onboard generation of nitrogen-enriched air (NEA) for fuel tank inerting offers significant advantages over the stored nitrogen concept currently in use. Additionally, the excess NEA generated in flight offers a potential fire extinguishing agent. To evaluate this potential, a small scale test apparatus was designed based on a survey of actual aircraft fires. Tow configurations, were used to simulate fires dominated by either forced convection or free convection. The fire types investigated were pool, spray, hot surface and combat damage. Test variables included air temperature, fuel type, fuel flow rate and surface temperature. Prior to developing conclusions on the effectiveness of NEA, verification tests were run using other common extinguishing agents (CO2, LN2, and Halon 1301). The quantity of agents required corresponded well with accepted levels based on previous tests. Several important findings were made. The data, presented in terms of volume percentage (air + extinguishant flow) of extinguishing agent required for fire knock-down, indicates the hot surface fire type to be the most severe. A volume concentration of 72% NEA9 (9% oxygen by volume ) was found to be effective in knocking down the hot surface fire. While this concentration is high, when compared on weight basis, NEA compares favorably with other agents.