An experimental study on fire behavior of an inclined ceiling jet in a low-pressure environment

Inclined ceiling jet fire may occur in a low-pressure aircraft cargo, which poses a great threat to airplane safety. To simulate an inaccessible area in cargo compartment, investigate the effects of pressure on the combustion characteristics of inclined ceiling jet fire, a series of fire experiments under an inclined ceiling (0 degrees, 15 degrees, 30 degrees, 45 degrees) in different pressure environments (50 kPa, 76 kPa, 101 kPa) were carried out in a full-size simulated cargo compartment. N-heptane square pool fires (20 x 20 x 5 cm), as radiation-controlled oil pool fires, were used as fire sources. The burning rate, heat radiation feedback, flame temperature, and ceiling temperature were measured and analyzed. The experiments showed that the heat radiation to pool surface had a significantly positive correlation with ambient pressure, and the penetration of thermal radiation made up a large proportion of heat radiation feedback, which should not be neglected for thin-layer oil burning. When the inclination angle was theta = 0 degrees or theta = 15 degrees, owing to the effects of ceiling, no significant differences existed on the rate of the axial flame temperature decrease in different pressure environments. Moreover, there were some fluctuations when flame was close to the ceiling. Based on previous models, new correlations to predict ceiling temperature in the upward direction and downward direction in different pressure environments were proposed, respectively.