Effect Of Obstacles On Flames

Abstract

The effect of distributed obstacles on flame propagation in gaseous media is studied numerically using a two-dimensional combustion hydrodynamic model. The method is applied to the problem of deflagration underneath a column-supported storage tank, idealized by a horizontal slice across the column array. Dimensions of the model problem are scaled down to expedite the computation. Numerical simulations confirms that distributed obstacles can accelerate a flame to many times its nominal speed. The results show that obstacles' cross-sectional area and separation distance are important factors in determining flame acceleration. The specific distribution of obstacles can also affect the speed of the flame, though not as much as the obstacles' size. The primary mechanism of flame acceleration in this study appears to be the aerodynamic effect due to obstruction of the flow. Also, the fastest moving flame branches are those propagating along line of-sight paths between the obstacles. The rate of flame propagation along each flame branch is controlled predominantly by the local flame and flow characteristics. The implication of these findings on the design of liquefied gaseous fuel (LGF) storage facilities are discussed.