Effect of surface gravity wave on liquid-phase heat transfer of flame spread over RP-3 under opposed flow

Abstract

Subflash temperature flame spread under opposed forced flow is controlled by heat transfer of subsurface flow depending on fuel thickness. In this work, the weakened subsurface flow by the surface gravity wave under opposed flow was observed, suggesting that the aerodynamic effect of opposed flow should be determined. Thus, flame propagation under the opposed flow was investigated where both shallow and deep pool condition are available. The flame spread rate and velocity of subsurface flow were determined by the measured position of flame front and leading edge of subsurface flow over time respectively. Results showed that the flame spread rate and relevant velocity of subsurface flow monotonically decrease with the opposed forced flow regardless of fuel depth. By introducing the velocity of surface wave that composed of Stokes drift speed and wind-drag speed, a new equation of subsurface flow velocity under opposed flow was proposed. Furthermore, a newly proposed model of flame spread rate was analytically established based on the modified velocity of subsurface flow, which has a higher forecasting accuracy than the previous model incorporating the effect of wind-induced gravity wave. This work facilitates the fundamental understanding of liquid fuel flame spread behavior under the action of wind-induced gravity wave.