Properties of laminar premixed CO/H₂/air flames at various pressures

Effects of positive flame stretch on the laminar burning velocities of CO/H₂/air mixtures were studied both experimentally and computationally for outwardly propagating spherical laminar premixed flames having concentrations of hydrogen in the fuel mixture of 3-50% by volume, fuel-equivalence ratios of 0.6-5.0, and pressures of 0.5-4.0 atm. Both measured and predicted ratios of unstretched to stretched laminar burning velocities varied linearly with Karlovitz numbers, yielding constant Markstein numbers for each reactant mixture and pressure. Effects of stretch on laminar burning velocities were modest at low hydrogen concentrations, but approached earlier results for hydrogen/air flames as hydrogen concentrations increased. Predicted and measured flame properties were in reasonably good agreement using several contemporary chemical reaction mechanisms.