Properties of laminar premixed hydrocarbon/air flames at various pressures

Outwardly propagating spherical laminar premixed names were experimentally and computationally used to find the sensitivities of laminar burning velocities to name stretch, represented by Markstein numbers, and the fundamental laminar burning velocities of unstretched flames. Conditions considered included ethane, ethylene, and propane/air flames 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) flames using mechanisms based on GRI-Mech, finding reasonably good agreement between measurements and predictions. An interesting experimental finding 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.