Suppression of Bluff-Body Stabilized Pool Flames

摘要

The suppression mechanisms of a nonpremixed flame stabilized behind a backward-facing step in a wind tunnel have been studied using a gaseous fire- extinguishing agent (Halon 1301, bromotrifluoromethane) into the airflow. Methane or JP-8 jet fuel was used to simulate a pool fire behind a clutter in the aircraft engine nacelle. The characteristic mixing time in the recirculation zone in the wake was measured by impulsively injecting salt water mist into the airflow and by determining a time constant for the exponential decay of the sodium D-line emission at high temperatures. For both methane and JP-8 fuels under relatively high air velocities, the dependence of the critical agent mole fraction at extinction on the injection period is predictable using the characteristic mixing time and the minimum agent mole fraction, which is a fuel property measurable by a steady-state cup-burner method.