Properties of Laminar Premixed Hydrocarbon/Air Flames at Various Pressures

Outwardly propagating spherical laminar premixed e ames were experimentally and computationally used to e nd the sensitivities of laminar burning velocities to e ame stretch, represented by Markstein numbers, and the fundamental laminar burning velocities of unstretched e ames. Conditions considered included ethane, ethylene, and propane/air e ames at fuel-equivalence ratios of 0.8 ‐1.6, and pressures of 0.5‐4.0 atm at normal temperatures. Predictions were limited to unstretched (plane) e ames using mechanisms based on GRI-Mech, e nding reasonably good agreement between measurements and predictions. An interesting experimental e nding was that Markstein numbers tended to become negative over broader ranges of fuel-equivalence ratios as the pressure increased, suggesting a greater propensity toward unstable combustion because of preferential-diffusion effects at the elevated pressures of interest for most practical applications.