Influence of depressurized environment on the fire behaviour in a dynamic pressure cabin

•Burning rate decreases linearly and is consistent with radiation modeling.•Flame height increases first and then decreases slightly as pressure decreases.•Regions of flame all elongate, in which temperature have different tendency.•Fire behaviour still keep the trend before in the transition stage. Aircraft cargo compartments usually undergo a dramatic pressure change during an emergency landing. Understanding fire behaviour in this dynamic-pressure environment is important for controlling aircraft fires. Pool fire experiments were conducted in a 3m×2m×4.65m cabin to analyze fire behaviour in an environment with varying pressure. A pressure control system was used to reduce cabin pressure during the fire. N-heptane pool fires with diameters of 20cm and 30cm were tested under depressurization from 101kPa to 24kPa with depressurization rates of 148Pa/s, 208Pa/s, 261Pa/s, and 304Pa/s. Fire behaviour such as burning rate, flame height, and flame temperature were analyzed. The results revealed that as the pressure is reduced, the burning rate decreases, which agrees with radiation modeling. Flame height increases as a power function of pressure while the peak time is earlier than the end time of depressurization. Three regions of flame all elongate and flame temperature in each region shows different trends. Moreover, there is a delay for the fire behaviour to reach the next quasi-steady stage after the depressurization, which can be divided into the transition stage.