Effects of ambient pressure and inclination angle on flame spread behaviors over polyester GFRP surface: Heat and mass transfer analysis

Abstract

Glass fiber-reinforced plastic (GFRP), a thermosetting plastic composed of glass fibers and polyester resin, is widely used in high-altitude regions. To elucidate the flame spread characteristics under low-pressure conditions, this study investigates the heat and mass transfer mechanisms during flame spread over the surface of polyester GFRP at various ambient pressures (60, 70, 80, and 90 kPa) and inclination angles (10°, 20°, and 30°) are analyzed. The results reveal that the pyrolysis front consistently exhibits an inverted ‘V’ shape, with its opening angle decreasing linearly as both pressure and inclination angle increase. Flame propagation across the material surface shows an accelerating trend, which becomes increasingly pronounced with higher inclination angles. Furthermore, the formation of a wall-like flame structure is supported by the exponential correlation between average flame length and heat release rate (L_f ∼ $\dot{Q}$^0.44). A dimensionless theoretical model for flame length, incorporating the effects of pressure and inclination angle, is also proposed. Additionally, convective and radiative heat fluxes are quantitatively analyzed with respect to variations in ambient pressure and inclination angle, elucidating the governing heat transfer mechanisms during flame spread.