Numerical simulation of fire suppression in aircraft compartment by refrigerant

Аuthors

Gurov L. V.

Company «Tupolev», 17, nab. Akademika Tupoleva, Moscow, 105005, Russia

e-mail: leonidgourov@yandex.ru

Abstract

This paper analyses the numerical results obtained in the transient CFD study of fire phenomena in the aircraft compartment that has a fire extinguisher system installed. To perform the study, a simplified 3D CAD model of the full-scale compartment with dedicated sprinklers to supply refrigerant (Freon 114B2) was considered. When setting the initial conditions for the calculation it was as sumed that some kind of fuel leakage occurred in the compartment so that its space is filled with a mixture of air and kerosene. To see how the final result is affected by the heat release rate of fire, this mixture was specified as stoichiometric for one simulation and as fuel-lean for the other one. A small igniter located in the lower part of the compartment is used to initiate the chemical processes. The refrigerant is supplied once the reaction zone becomes large enough so that temperature exceeds the critical value in certain regions, where thermal sensors are supposed to be installed. The ignition and combustion processes were simulated using a simplified kinetic model that includes 77 chemical reactions for 30 components, where kerosene is represented in the form of C12H23 molecule. This model was supplemented with the Freon 114B2 molecule of C2Br2F4 (gaseous phase) that was accounted for in the chemical reactions where third body was present. Further assumption was made regarding the refrigerant streams supplied – it was suggested that as the stream exits the sprinkler it does break up immediately into droplets that are treated in the computation as Lagrangian particles coupled with Ranz–Marshall evaporation model. Thus, the energy released in the chemical reactions gets absorbed with the evaporated particles as they fall into the fire area. When calculating the vapor pressure at the given temperature for the refrigerant considered, Antoine equation is used, while the latent heat of vaporization is determined using Clausius-Clapeyron equation. The results obtained in the calculations indicate that for the given model of aircraft compartment with two sprinklers installed and refrigerant supplied at 8 kg/s rate fire suppression lasts about 0,7 sec. Yet, the refrigerant streams supplied from the sprinkler are also notable for enhancing the mixing of burnt/unburnt regions – this has a significant impact on the production rate of the combustion products during the first 0,1 sec.

Keywords:

Navier–Stokes equations, chemical kinetics, multiphase flow, droplet evaporation, fire extinguisher system

References

1. The TU-145B aircraft. Operation and maintenance manual. Book 2. Part 1, 1975. 162 p.
2. Airworthiness standards for NLG 25 transport category aircraft (Part 25). Мoscow: Federal'noe Agentstvo vozdushnogo transporta; 2022. 355 p.
3. Hewson J, Tieszen S, Sundberg W et al. CFD modeling of fire suppression and its role in optimizing suppressant distribution. Proceedings of the Halon options technical conference, 2003.
4. Meredith KV. Fire Suppression Modeling with Computational Fluid Dynamics: State of the Art. Proceedings of the Ninth International Seminar on Fire and Explosion Hazards (April 21–26, Saint Petersburg, Russia).
5. Gokulakrishnan P, Joklik R, Viehe D et al. Optimization of Reduced Kinetic Models for Reactive Flow Simulations. Journal of Engineering for Gas Turbines and Power. 2014;136(1).
6. Akerblom A. LES modelling of spray combustion. PhD Thesis, Lund University. 2021. 90 p.
7. Fire extinguishers of type 1M and 2M. Technical operation Manual, APS-6600-6300 RE. 1987. 38 p.
8. Dembele S, Dombrovsky L. Modelling fire suppression by water sprays in CFD: a review of progresses and challenges. 18th International Water Mist Conference (19-20 September 2018; London).
9. Zettervall N, Fureby C, Nilsson EJK. A reduced chemical kinetic reaction mechanism for kerosene-air combustion. Fuel. 269. DOI: 10.1016/j.fuel.2020.117446
10. Snegirev AYu, Sazhin SS, Talalov VA. Model and algorithm for calculating heat transfer and evaporation of droplets of dispersed liquid. Nauchno-tekhnicheskie vedomosti Sankt-Peterburgskogo gosudarstvennogo politekhnicheskogo universiteta. Fiziko-matematicheskie nauki. 2011;(1 (116)):44–55.
11. Stephenson RM, Malanowski S. Handbook of the Thermodynamics of Organic Compounds. Elsevier. New York. 1987. 552 p.
12. Ranz W, Marshall W. Evaporation from Drops. Chemical Engineering Progress. 1952:(48):141–146.