Investigation on the CO concentration decay profile and spread velocity of a ceiling jet at reduced pressure in aircraft cargo compartment fires

The transport of carbon monoxide (CO) induced by an aircraft cargo compartment fire is fundamental in the development of a multi-sensor fire detection system. On the basis of fire tests carried out in a full scale simulated aircraft cargo compartment at 100 kPa, 90 kPa, 80 kPa and 70 kPa which corresponds to the pressure within an actual aircraft cargo compartment from the sea level to the cruising altitude (about 10,000 m), further numerical simulations were conducted by Fire Dynamics Simulator (FDS) to investigate the influence of reduced pressure on CO concentration spread and decay profile of a ceiling jet. CO concentration profile is found to be divided into two phases, where CO concentration fluctuates wildly in phase one of 0 <= r/H <= 0.5 close to plume impingement region, and then CO concentration decays smoothly and slowly in phase two of 0.5 <= r/H <= 2.0. Accordingly empirical correlations are proposed to describe CO concentration decay profile. Through comparison of CO concentration clouds at different pressures versus time, CO concentration spread velocity is obtained to show that CO spreads faster at reduced pressure. (C) 2017 Elsevier Ltd. All rights reserved.