Experimental study on two-dimensional propagating edge flames: cold flow modeling and flame spread rate measurements

This thesis presents the results of an experimental study on two-dimensional, planar propagating edge flames. The results were generated using a new apparatus in which a thin stream of gaseous fuel is injected into a low-speed laminar wind tunnel thereby forming a flammable layer along the centerline. The fuel injector consists of aluminum airfoil with a thin slot in its trailing edge, from which fuel is injected. After the initial stratified fuel/air layer is developed, a flame is ignited near the tunnel outlet, and the flame spreads against the incoming air, toward the fuel source. Experiments were conducted with methane and ethane, with the apparatus mounted vertically such that air and fuel flow is upward while the flame spread is downward. Experiments were conducted with air velocity of 25 to 60 cm/s and fuel flows of 967 to 3036 ccm, resulting in centerline equivalence ratios between 0.5 and 2.0. Experiments results showed that the measured flame speed exceeds the laminar flame spread rate and is a function of the gradient of the equivalence ratio perpendicular to the direction of the flame spread. Prior to conducting the combustion experiments, the apparatus was characterized using a steady-state numerical model of the non-reacting flow developed using the COSMOSFloWorks commercial computational fluid dynamics code. The model provided insights into the behavior of the fuel distribution in the gallery prior to ignition. The COSMOSFloWorks model agreed well with detailed measurements of velocity profiles in the gallery, which were conducted to ensure that the flow field was laminar prior to ignition. The practical extension of this work would be in fire safety in normal and microgravity. Non-uniform mixtures can form in normal gravity at crash sites, along ceiling in mining operations, and fuel spills. Non-uniform mixtures can also form in microgravity and knowing the conditions and possible flame spread phenomenon would be beneficial when designing spacecraft components or terrestrial environments