Flame Extinction Limits of H2‐CO Fuel Blends

The flame extinction limits of syngas $(H2‐CO)$ flames were measured using a twin-flame counterflow burner. Plots of extinction limits (⁠$%f$⁠: volumetric percent of fuel in air) versus global stretch rates were generated at different fuel blend compositions and were extrapolated to determine the flame extinction limit corresponding to an experimentally unattainable zero-stretch condition. The zero-stretch extinction limit of $H2‐CO$ mixtures decreases with the increase in $H2$ concentration in the mixture. The average difference between the measured flame extinction limit and the Le Chatelier’s calculation is around 7% of the mean value. The measured OH chemiluminescence data indicates that regardless of blend composition the OH radical concentration reduces to a critical value prior to the flame extinction. The measured laminar flame velocity close to the extinction indicates that regardless of fuel composition, the premixed flame of hydrogen fuel blends extinguishes when the mixture laminar flame velocity falls below a critical value.