Numerical analysis of the flow characteristics of ultra-fine powder extinguishing agent in aircraft fire suppression system

The effectiveness of an aircraft nacelle fire suppression system largely depends on the design of the system, specifically on the flow and diffusion of the extinguishing agent. Through simulation studies of a particular aircraft nacelle ultra-fine powder extinguishing system, the results indicate that the nozzles located in the fan compartment ejected more mass of extinguishing agent compared to the nozzles located in the core compartment. The maximum mass flow for injection was 0.649 kg/s, and the overall injection time was 1.8 s. Additionally, at the same inlet air flow, the duration of the extinguishing agent concentration was shorter for higher initial temperatures, and the duration in the core compartment was shorter compared to the fan compartment. For instance, at an initial inlet air temperature of 121 °C and a single inlet air flow of 0.13 kg/s, the minimum duration in the core compartment was 0.93 s. Finally, under various ventilation and temperature conditions, the concentration of ultra-fine powder extinguishing agent exceeded 80g/m3 and maintained above 0.5 s to fulfil the design requirements for the fire suppression system.