A study on flame structure and extinction in downstream interaction between lean premixed CH sub(4-air and (50% H) sub(2) + 50% CO) syngas-air flames

• Published in: International journal of hydrogen energy Vol. 36; no. 9; pp. 5717 - 5728
• Main Authors: Kim, Jeong Soo, Park, Jeong, Kwon, Oh Boong, Bae, Dae Seok, Yun, Jin Han, Keel, Sang In
• Format: Journal Article
• Language: English
• Published: 01-05-2011
• Subjects: Boundaries; Carbon monoxide; Extinction; Flame speed; Flame temperature; Hydrocarbons; Premixed flames
• ISSN: 0360-3199
• DOI: 10.1016/j.ijhydene.2011.02.037

Downstream interactions between lean premixed flames with mutually different fuels of (50% H sub(2 + 50% CO) and CH) sub(4) are numerically investigated particularly on and near lean extinction limits in order to provide fundamental database for the design of cofiring burners with hydrocarbon and syngas under a retrofit concept. In the current study the anomalous combination of lean premixed flames is provided such that even a weaker CH sub(4-air flame temperature is higher than a stronger syngas-air flame temperature, and, based on a deficient reactant concept, the effective Lewis numbers Le) sub(e)ff [asymptotic to] 1 for lean premixed (50% H sub(2 + 50% CO)-air mixture and Le) sub(D) < 1 for CH sub(4-air mixture. It is found that the interaction characteristics between lean premixed (50% H) sub(2) + 50% CO)-air and CH sub(4-air flames are quite different from those between the same hydrocarbon flames. The lean extinction boundaries are of slanted shape, thereby indicating strong interactions. The upper extinction boundaries have negative flame speeds while the lower extinction boundaries have both negative and positive flame speeds. The results also show that the flame interaction characteristics do not follow the general tendency of Lewis number, which has been well described in interactions between the same hydrocarbon flames, but have the strong dependency of direct interaction factors such as flame temperature, the distance between two flames, and radical-sharing. Importance of chain carrier radicals such as H is also addressed in the downstream interactions between lean premixed (50% H) sub(2) + 50% CO)-air and CH sub(4-air flames.)