Opposed Flow Impact on Flame Spread Above Liquid Fuel Pools

Three-dimensional unsteady Navier-Stokes computations have been performed for the ignition and ame propagation above a liquid fuel (propanol) pool in an air ow duct. Pulsating ame spread behavior occurs if the initial liquid temperature and/or the oxygen mass fraction in the incoming air ow is suciently low. The roles of surface-tension-driven ow, gas buoyancy, liquid buoyancy, and hot gas expansion are analyzed. The eects of oxygen mass fraction, pool depth, and pool width are evaluated. An extensive parameter survey determines the regimes of pulsating ame spread and uniform ame spread in the initial temperature/opposed air velocity, pool depth, pool width, or oxygen concentration plane. The two regimes are dened for both earth gravity and microgravity conditions. For narrow pools (2cm), the three-dimensional eects are focused near the poolside edges where the ame front wraps along the poolside edge but remains nearly two-dimensional over most of the pool. For a wider pool (8cm), three-dimensional variations in ame shape occur over much of the pool. The behavior of the ame along the poolside edges diers signicantly for earth gravity and microgravity conditions. The supply of oxygen due to buoyancy at the edges is an important factor.