Experimental Study on the Stability of a Diffusion Flame Established in a Laminar Boundary Layer

Clearly defined aspects of fire safety are flame propagation and mass bunting. When a heat source is in contact with a combustible material ignition may occur. Once the fuel is ignited, the flame propagates across its surface and establishes a diffusion flame over the fuel. The flame transfers heat to the surface, the combustible material vaporizes, and this vapor provides the gaseous fuel necessary to sustain the flame. This process is called mass burning. In normal gravity, temperature gradients generated by the chemical reaction, cause natural convective flows. These flows are initially laminar and transition to turbulence as the area of the burning surface increases. In spacecraft, where buoyancy is negligible, no convective flow develops and flow is limited to that induced by the ventilation system. Since characteristic ventilation velocities are of the order of 0.1 m/s, the flow can be expected to remain laminar and parallel to the surface of the fuel. The complex, often turbulent, mixed flow scenario observed in normal gravity turns into a classical combustion problem generally referred to in the literature as "The Emmons Problem". The main assumptions behind this theory are of great relevance to spacecraft fire safety and since the solution neglects gravity, have yet to be verified.