Effect of discharged pressure for fire extinguishing agent performance (HFC-125) considering fire accident in the aviation

Abstract

HFC-125 (fire extinguishing agent) affects the charged pressure inside the vessel depending on the ambient temperature. Aviation fire extinguishing systems are exposed to ambient temperatures ranging from −50 °C to 200 °C. In this study, experiments were conducted at changing charged pressure, high ambient temperature, and low ambient temperature under the assumption that the pressure inside the vessel changes depending on the ambient temperature. The charged pressure range is 3.61 MPa–4.90 MPa. It was confirmed that as the charged pressure increased, the discharge time decreased from 2.19 s to 1.67 s and pressure recovery occurred. The charged pressure range where pressure recovery occurs was predicted to be 2.63 MPa–5.12 MPa. The pressure recovery showed the largest pressure difference at 4.21 MPa of charged pressure. In the high temperature experiments, the ambient temperatures were 56 °C and 76 °C, and chalked flow occurred above 56 °C. This means that the discharge rate is constant above 56 °C. In low temperature experiments, HFC-125 was lowered to below −30 °C and discharged at −14 °C and −18.8 °C. The low temperature experiment results showed that pressure recovery did not occur at low temperatures due to unsaturation of dissolved nitrogen. Additionally, oscillations also occurred, resulting in discontinuous discharge rate.