Experimental Study of N-Heptane Pool Fire Behaviors under Dynamic Pressures in an Altitude Chamber

Abstract The experimental observation of pool fires under dynamic pressure is of significant meaning to understand the fire behaviors under different low pressure environments. Previous studies on low-pressure fires mainly focused on fire behaviors at static low pressure, where the fire tests were usually conducted at several discrete altitudes. An altitude chamber of size 3 m× 2 m× 2 m has been built for this study, where different dynamic pressure descent rates were configured to simulate pool fire behaviors under different low pressures. In each test, the chamber pressure varies from standard atmospheric pressure 101.3 KPa to 34 KPa. The dynamic pressure descent rate is controlled by replenishing air at different rates: 0, 15 and 20 Nm3/h. The study tested two different sizes of pool fires, where the pan heights are all 2 cm and the pan diameters are 6 cm and 10 cm respectively. N-Heptane with industrial purity of 99% was used as the testing fuel. Parameters were measured along the whole burning process, including axial flame temperature, burning rate, radiative heat flux, chamber pressure as well as fire video recording. Some specific phenomena were observed for the fires under dynamic depressurization, e.g. the flame transmitted from turbulent to laminar and its base turned blue as pressure drops, then in the final burning stage a polyhedral flame appeared and swirled in the pan until extinguishment. The measurement data, i.e. mass burning rate, flame temperature and radiative heat flux, were analyzed to reveal the pressure effect in influencing fire behaviors.