Fire suppression using trifluoroiodomethane (CF3I)-carbon dioxide (CO2) mixtures

With the regulatory prohibition for using Halon 1301 (CF3Br) in fire suppression systems onboard newly certified aircraft, significant research efforts have been undertaken to develop suitable halon replacements with comparable suppression performance that are also eco-friendly with low Ozone Depletion Potential (ODP) and Global Warming Potential (GWP). This paper determined the fire suppression effectiveness for mixtures of trifluoroiodomethane (CF3I) with carbon dioxide (CO2) under development as a drop-in halon replacement for onboard aircraft fire suppression systems. Through both experimental measurements and flame simulations using detailed chemical kinetics, we demonstrated that the extinguishment performance of CF3I-CO2 blends can be superior to that of the individual components alone. The extinction concentrations were determined for different CF3I-to-CO2 ratios introduced into ambient air using a heptane cup burner. The extinction concentrations for pure CF3I in air (3.36 ± 0.13% vol.) and CO2 in air (20.74 ± 0.64% vol.) are in close agreement with previously reported values, and first-time extinction concentration data for CF3I-CO2 blends are reported. To elucidate important reaction pathways, detailed chemical mechanisms have been compiled for modeling methane-, propane- and heptane-air flame inhibition at ambient conditions. These mechanisms were constructed from published sub-mechanisms for C7 and C1-C3 hydrocarbons and hydrofluorocarbons with additional oxidation chemistry developed for trifluoroiodomethane. The latter sub-mechanism contains 14 species and 91 reactions. Using the CANTERA software package, critical concentration values of CF3I-CO2 mixtures in air for extinguishing methane, propane, and n-heptane counterflow flames were determined and compared against experimental non-premixed flame extinction data.