Factors affecting the burning rate of pool fire in a depressurization aircraft cargo compartment

•The sudden ventilation activates the fire greatly at the beginning of the depressurization.•The influence level of ventilation weakens gradually with the decrease of pressure.•The dimensionless ventilation factor Qρṁp,∞″S has a linear relationship with burning rate.•The faster depressurization rate causes a larger dimensionless ventilation factor and increases the burning rate peak. A full-scale below-floor cargo compartment with the size of 8.11 m × 4.16 m × 1.67 m was used to simulate a depressurized environment for an aircraft fire during flight. Pool fire experiments with 20 cm n-heptane at four depressurization rates of 6 kPa/min, 12 kPa/min, 17 kPa/min, and 20 kPa/min were carried out. The fuel mass, compartment pressure, vent flow rate, and oxygen concentration were measured. The results indicate that ventilation increases the burning rate drastically at the beginning of depressurization, and then its dominant role gradually weakens with a decrease in pressure. A dimensionless ventilation factor qρṁp,∞″S proved to have a linear relationship with the burning rate. In addition, a faster depressurization rate increases the peak of the burning rate. The above conclusions indicate that a fire in the compartment has the greatest risk when the ventilation begins, and the depressurization rate should be as low as possible to reduce the fire hazard.