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Author

Yoo, Chun Sang
Combustion & Propulsion Lab
Research Interests
  • Numerical turbulent combustion

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Three-dimensional direct numerical simulation of a turbulent lifted hydrogen jet flame in heated coflow: a chemical explosive mode analysis

Cited 36 times inthomson ciCited 32 times inthomson ci
Title
Three-dimensional direct numerical simulation of a turbulent lifted hydrogen jet flame in heated coflow: a chemical explosive mode analysis
Author
Lu, T. F.Yoo, Chun SangChen, J. H.Law, C. K.
Keywords
Air slot; Auto-ignition; Characteristic time; Chemical explosive; Chemical sources; Co-flow; Complex flow; Conventional methods; Explosion process; Flame front; Grid points; Heated air; Hydrogen jets; Jet flames; Lifted flames; Mode analysis; Near-field structure; Premixed Flame; Scalar dissipation rate; Thermal runaways; Time-scales
Issue Date
201006
Publisher
CAMBRIDGE UNIV PRESS
Citation
JOURNAL OF FLUID MECHANICS, v.652, no., pp.45 - 64
Abstract
A chemical explosive mode analysis (CEMA) was developed as a new diagnostic to identify flame and ignition structure in complex flows. CEMA was then used to analyse the near-field structure of the stabilization region of a turbulent lifted hydrogen air slot jet flame in a heated air coflow computed with three-dimensional direct numerical simulation. The simulation was performed with a detailed hydrogen air mechanism and mixture-averaged transport properties at a jet Reynolds number of 11 000 with over 900 million grid points. Explosive chemical modes and their characteristic time scales, as well as the species involved, were identified from the Jacobian matrix of the chemical source terms for species and temperature. An explosion index was defined for explosive modes, indicating the contribution of species and temperature in the explosion process. Radical and thermal runaway can consequently be distinguished. CEMA of the lifted flame shows the existence of two premixed flame fronts, which are difficult to detect with conventional methods. The upstream fork preceding the two flame fronts thereby identifies the stabilization point. A Damkohler number was defined based on the time scale of the chemical explosive mode and the local instantaneous scalar dissipation rate to highlight the role of auto-ignition in affecting the stabilization points in the lifted jet flame.
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DOI
http://dx.doi.org/10.1017/S002211201000039X
ISSN
0022-1120
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