Numerical analysis of deflagration initation by a hot jet

Iglesias Estradé, Inmaculada and Vera Coello, Marcos and Sánchez Pérez, Antonio Luis and Liñán Martínez, Amable (2012). Numerical analysis of deflagration initation by a hot jet. "Combustion Theory and Modelling", v. 16 (n. 6); pp. 994-1010. ISSN 1364-7830.


Title: Numerical analysis of deflagration initation by a hot jet
  • Iglesias Estradé, Inmaculada
  • Vera Coello, Marcos
  • Sánchez Pérez, Antonio Luis
  • Liñán Martínez, Amable
Item Type: Article
Título de Revista/Publicación: Combustion Theory and Modelling
Date: 2012
Volume: 16
Faculty: E.T.S.I. Aeronáuticos (UPM)
Department: Motopropulsión y Termofluidodinámica [hasta 2014]
Creative Commons Licenses: Recognition - No derivative works - Non commercial

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Numerical simulations of axisymmetric reactive jets with one-step Arrhenius kinetics are used to investigate the problem of deflagration initiation in a premixed fuel–air mixture by the sudden discharge of a hot jet of its adiabatic reaction products. For the moderately large values of the jet Reynolds number considered in the computations, chemical reaction is seen to occur initially in the thin mixing layer that separates the hot products from the cold reactants. This mixing layer is wrapped around by the starting vortex, thereby enhancing mixing at the jet head, which is followed by an annular mixing layer that trails behind, connecting the leading vortex with the orifice rim. A successful deflagration is seen to develop for values of the orifice radius larger than a critical value a c in the order of the flame thickness of the planar deflagration δL. Introduction of appropriate scales provides the dimensionless formulation of the problem, with flame initiation characterised in terms of a critical Damköhler number Δc=(a d/δL)2, whose parametric dependence is investigated. The numerical computations reveal that, while the jet Reynolds number exerts a limited influence on the criticality conditions, the effect of the reactant diffusivity on ignition is much more pronounced, with the value of Δc increasing significantly with increasing Lewis numbers. The reactant diffusivity affects also the way ignition takes place, so that for reactants with the flame develops as a result of ignition in the annular mixing layer surrounding the developing jet stem, whereas for highly diffusive reactants with Lewis numbers sufficiently smaller than unity combustion is initiated in the mixed core formed around the starting vortex. The analysis provides increased understanding of deflagration initiation processes, including the effects of differential diffusion, and points to the need for further investigations corporating detailed chemistry models for specific fuel–air mixtures.

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Item ID: 32538
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Deposited by: Biblioteca ETSI Aeronauticos
Deposited on: 31 Oct 2014 07:24
Last Modified: 31 Oct 2014 07:24
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