Critical radius for sustained propagation of spark-ignited spherical flames

• Published in: Combustion and flame Vol. 156; no. 5; pp. 1006 - 1013
• Main Authors: Kelley, Andrew P., Jomaas, Grunde, Law, Chung K.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.05.2009; Elsevier
• Subjects: ADVANCED PROPULSION SYSTEMS; AIR; Applied sciences; BUTANE; COMBUSTION; Critical radius; Energy; Energy. Thermal use of fuels; Engines and turbines; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; FLAME PROPAGATION; HYDROGEN; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; LAMINAR FLAMES; LEWIS NUMBER; MATHEMATICAL SOLUTIONS; Minimum radius; Outwardly propagating flames; PRESSURE RANGE KILO PA; Spark ignition; SPARK IGNITION ENGINES; SPHERICAL CONFIGURATION; Spherical flames; Spark ignition; Minimum radius; Laminar flames; Spherical flames; Critical radius; Outwardly propagating flames; Laminar flame; Hydrogen; Combustion; Spark ignition engine; Experimental study; Flame propagation; Butane; Lewis number; Flame structure; Internal combustion engine
• ISSN: 0010-2180; 1556-2921
• DOI: 10.1016/j.combustflame.2008.12.005

An experimental study was performed to determine the requirements for sustained propagation of spark–ignited hydrogen–air and butane–air flames at atmospheric and elevated pressures. Results show that sustained propagation is always possible for mixtures whose Lewis number is less than unity, as long as a flame can be initially established. However, for mixtures whose Lewis number is greater than unity, sustained propagation depends on whether the initially ignited flame can attain a minimum radius. This minimum radius was determined for mixtures of different equivalence ratios and pressures, and was found to agree moderately well with the theoretically predicted critical radius beyond which there is no solution for the adiabatic, quasi-steady propagation of the spherical flame. The essential roles of pressure, detailed chemistry, and the need to use local values in the quantitative evaluation of the flame response parameters are emphasized.