Abstract:

To investigate the effects of weak gravitational motion conditions on pool fire combustion during aircraft takeoff and landing, an inclined test platform with inclination angles ranging from 15° to 45° was first built to simulate the composite weak gravity conditions of aircraft takeoff and landing. Square fuel pools of different sizes were adopted, and sensors and high-speed cameras were used to collect data including acceleration, flame morphology and fuel burning duration. Next, the flame evolution during the sliding process was observed, and three stages were identified: initial stable stage, rapid tilting stage and oscillatory stabilization stage. The influences of inclined angle and pool size on fuel burning rate, flame tilt angle and flame height were analyzed, and the internal mechanism of flame deflection and height reduction under the combined effect of gravity and horizontal inertial force was clarified. Finally, equivalent simplification was carried out based on the laminar stagnation layer theory, and quantitative correlation models between burning rate, flame tilt angle, flame height and gravity as well as horizontal acceleration were established, respectively. The results show that the burning rate of n-heptane under sliding conditions is higher than that under static conditions. The mass loss rate of n-heptane increases first and then decreases with the rise of sliding angle, reaching its peak at 25-35°. As the pool size increases, the sensitivity of n-heptane flame tilt angle to variations in gravity and horizontal acceleration rises, while the sensitivity of flame height to such variations declines.

Key words: weak gravity, motion condition, n-heptare, mass loss rate, flame height, flame inclination angle