Fire Safety Science Digital Archive

Experiments are conducted to study the effect of buoyancy on the pulsation frequency of a diffusion flame stabilized on a horizontal surface. A pool fire is simulated, in a pressure vessel, by injecting a gaseous fuel through a porous flat horizontal burner; air for combustion is introduced at low velocity from below the burner. The flame behavior is investigated at different gravity levels from reduced gravity to centrifuge conditions - 12 times normal gravity (atmospheric pressure) and at ambient pressures ranging from 0.03 MPa to 0.3 MPa (normal gravity). To model the puffing phenomena, Navier Stokes equations are arranged to define a characteristic equation for gravity wave propagation those celerity is related to flame frequency. This wave propagates horizontally inducing an integer number of nodes n. Its wave length depends on the mode selection and is expressed as the root mean square of gravity. The vertical convection deteriorates the gravity wave, leading to instable flow. The three-dimensional gravity wave induces the puffing phenomenon.