Modeling the formation of flammable atmospheres within cylindrical containers containing some liquid fuel

Abstract

A two-dimensional axisymmetric mathematical model has been developed to describe the transient formation of flammable atmospheres within the confines of a partially empty open-topped liquid fuel container. The model was numerically solved using a finite volume scheme. The formulation included consideration of local changes in density and thermophysical properties of the formed gaseous mixtures due to the concentration and temperature variations within the container. The flammable zone was assumed to be defined by all the spatial locations inside the container where the fuel vapor concentration is within the lean and the rich flammable concentrations range. It was found that the transient development of the flammable zone above the liquid-gas interface was controlled by the combined effects of molecular and convective diffusion of the fuel vapor from interface. The fuel vapor diffusion and mixing process was also enhanced by natural convection, which was induced by the presence of temperature and concentration gradients within the container. Different flammable zone development regimes evolve that depend on the fuel properties, the fuel flammable concentration range, and the surrounding ambient conditions. Two liquid fuels, namely n-pentane and methanol, are considered to address some of the effects related to fuel properties and the fuel flammable concentration range. The effect of the surrounding ambient temperature conditions on the development of the flammable zone is also considered.