A mechanistic study of Soret diffusion in hydrogen-air flames

Journal Article · Fri Jan 15 04:00:00 EST 2010 · Combustion and Flame

DOI:https://doi.org/10.1016/J.COMBUSTFLAME.2009.09.018· OSTI ID:21248858

Yang, F ^[1]; Law, C K ^[1]; Sung, C J ^[2]; Zhang, H Q ^[3]

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1. Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544 (United States)
2. Department of Mechanical Engineering, University of Connecticut, Storrs, CT 06269 (United States)
3. Department of Engineering Mechanics, Tsinghua University, Beijing (China)

The separate and combined effects of Soret diffusion of the hydrogen molecule (H{sub 2}) and radical (H) on the structure and propagation speed of the freely-propagating planar premixed flames, and the strain-induced extinction response of premixed and nonpremixed counterflow flames, were computationally studied for hydrogen-air mixtures using a detailed reaction mechanism and transport properties. Results show that, except for the conservative freely-propagating planar flame, Soret diffusion of H{sub 2} increases the fuel concentration entering the flame structure and as such modifies the mixture stoichiometry and flame temperature, which could lead to substantial increase (decrease) of the flame speed for the lean (rich) mixtures respectively. On the other hand, Soret diffusion of H actively modifies its concentration and distribution in the reaction zone, which in turn affects the individual reaction rates. In particular, the reaction rates of the symmetric, twin, counterflow premixed flames, especially at near-extinction states, can be increased for lean flames but decreased for rich flames, whose active reaction regions are respectively located at, and away from, the stagnation surface. However, such a difference is eliminated for the single counterflow flame stabilized by an opposing cold nitrogen stream, as the active reaction zone up to the state of extinction is always located away from the stagnation surface. Finally, the reaction rate is increased in general for diffusion flames because the bell-shaped temperature distribution localizes the H concentration to the reaction region which has the maximum temperature. (author)

• OSTI ID: 21248858
• Journal Information: Combustion and Flame, Journal Name: Combustion and Flame Journal Issue: 1 Vol. 157; ISSN CBFMAO; ISSN 0010-2180
• Country of Publication: United States
• Language: English

Related Subjects

08 HYDROGEN
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
AIR
COMBUSTION KINETICS
COMBUSTION PROPERTIES
DIFFUSION
FLAME EXTINCTION
FLAME PROPAGATION
FLAMES
Fickian diffusion
Flame structure
HYDROGEN
MIXTURES
MOLECULES
NITROGEN
RADICALS
SPATIAL DISTRIBUTION
STAGNATION
STOICHIOMETRY
STRAINS
SURFACES
Soret diffusion
TEMPERATURE DISTRIBUTION
VELOCITY
ZONES