Effects of pool dimension on flame spread of aviation kerosene coating on a metal substrate

Abstract

Experimental investigations are undertaken to study flame spread over aviation kerosene coating on a metal substrate with various pool dimensions. According to the experimental data, flame spread over aviation kerosene is separated into shallow and deep pool for fuel depth of 4.0mm, as well as narrow and wide pool for pool width of 12cm. The variation of flame spread velocity with pool dimension indicates that flame spread accidents on wide or deep pools are potentially more hazardous. Meanwhile, the critical liquid depth is defined as the minimum fuel depth for supporting flame propagation. For pool narrower than 16cm, the critical liquid depth declines inversely proportionally with an increase in pool width. For pool wider than 16cm, however, the critical liquid depth stabilizes at 1.2mm. At critical liquid depth, theoretical analysis verifies that surface deformation possesses a significant effect on flame extinction. The division criterion for deep and shallow pool is also validated by scaling analyses: the values of characteristic length scale ratio (ht/L) and Ra/Ma increase steeply under shallow pool conditions, but remain stable under deep pool conditions. Moreover, the variation trend of Ra/Ma confirms that Marangoni force dominates buoyancy force in driving flame spread at any fuel depths, whereas buoyant effect performs an increasingly importance as the fuel depth increases. Furthermore, the calculated Prandtl number demonstrates that the decrease of flame spread velocity for shallow pool is mainly caused by viscous shear on the metal substrate surface and secondarily caused by heat losses.