Flashback Propensity of Syngas Fuels Available to Purchase

The paper presents experimental measurements of flashback propensity of H₂-CO mixtures (primary constituents of syngas fuels). Effects of H₂ concentration, external excitation and swirl on the flashback propensity of H₂-CO flames are discussed. The flashback behavior of H₂-CO flames changes nonlinearly with the increase in H₂ contents in the mixture. The critical velocity gradient (g_F) values of 5%–95% and 15%–85% H₂-CO mixtures somewhat agree with the scaling relation (g_F = c(S_L²/α)) and yield an average c value of 0.035. However, the g_F values of 25%–75% H₂-CO mixture show higher order variations with the S_L²/α ratio (especially for S_L²/α < 19,000 s⁻¹). At a lower S_L²/α ratio, burner diameters have small effects on critical velocity gradient measurements; however, the effect is significant at higher S_L²/α ratio. The effect of external excitation on the flashback propensity of H₂-CO flames with more than 5% H₂ is not significant. Flashback through two mechanisms and their dependence on combustor parameters were also identified for swirl stabilized H₂-CO flames.