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Flow field of a diffusion flame attached to a thick-walled injector between two coflowing reactant streams

Published online by Cambridge University Press:  26 April 2006

F. J. Higuera  and
A. Liñán
F. J. Higuera
Affiliation:
ETS Ingenieros Aeronáuticos, Pza. Cardenal Cisneros 3, 28040 Madrid, Spain
A. Liñán
Affiliation:
ETS Ingenieros Aeronáuticos, Pza. Cardenal Cisneros 3, 28040 Madrid, Spain
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Abstract

The flow field of a diffusion flame attached to a thick-rim injector between two coflowing streams of fuel and oxidiser is analysed in the Burke–Schumann limit of infinitely fast reaction rate. The length of the recirculation region immediately behind the injector and the velocity of the recirculating fluid are proportional to the shear stresses of the reactant streams on the wall of the injector for a range of rim thicknesses, and the structure of the flow in the wake depends then on three main non-dimensional parameters, measuring the gas thermal expansion due to the chemical heat release, the air-to-fuel stoichiometric ratio of the reaction, and the air-to-fuel ratio of wall shear stresses. The recirculation region shortens with increasing heat release, and the position of the flame in this region depends on the other two parameters. An asymptotic analysis is carried out for very exothermic reactions, showing that the region of high temperature around the flame is confined by neatly defined boundaries and the hot fluid moves like a high-velocity jet under a favourable self-induced pressure gradient. The immediate wake is surrounded by a triple-deck region where the interacting flow leads to an adverse pressure gradient and a reduced shear stress upstream of the injector rim for sufficiently exothermic reactions. Separation of the boundary layers on the wall of the injector, however, seems to be postponed to very large values of the gas thermal expansion.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 329 , 25 December 1996 , pp. 389 - 411
Copyright
© 1996 Cambridge University Press

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References

Gaydon, A. G. & Wolfhard, H. G. 1953 Flames–Their Structure, Radiation, and Temperature, p. 39. Chapman & Hall.
Goldstein, S. 1930 Concerning some solutions of the boundary-layer equations in hydrodynamics. Proc. Camb. Phil. Soc. 26, 1–30.Google Scholar
Hakkinen, R. J. & Rott, N. 1965 Similarity solutions for merging shear flows II. AIAA J. 3, 1553–1554.Google Scholar
Kawamura, T. & Asato, K. 1975 The structure of the stabilizing region of a laminar fuel jet flame. Proc. 2nd European Symp. on Combustion, pp. 611–616. The Combustion Institute, Pittsburgh.
Kawamura, T., Asato, K. & Mazaki, T. 1980 Structure analysis of the stabilizing region of plane, laminar fuel-jet flames. Combust. Sci. Tech. 22, 211–216.Google Scholar
Lewis, B. & Elbe, G. VON 1961 Combustion, Flames and Explosions of Gases, 3rd. edn., pp. 233–236. Academic Press.
Liñán, A. 1974 The asymptotic structure of laminar diffusion flames for large activation energies. Astro. Acta 1, 1007–1031.Google Scholar
Liñán, A. 1994 Ignition and flame spread in laminar mixing layers. In Combustion in High Speed Flows (ed. J. Buckmaster et al.), pp. 461–476. Kluwer.
Messiter, A. F. 1970 Boundary layer flow near the trailing edge of a flat plate. SIAM J. Appl. Maths 18, 241–257.Google Scholar
Robson, K. & Wilson, M. J. G. 1969 The stability of laminar diffusion flames of methane. Combust. Flame 13, 626–634.Google Scholar
Smith, F. T. 1982 On the high Reynolds number theory of laminar flows. IMA J. Appl. Maths 28, 207–281.Google Scholar
Stewartson, K. 1969 On the flow near the trailing edge of a flat plate II. Mathematika 16, 106–121.Google Scholar
Takahashi, F., Mizomoto, M., Ikai, S. & Futaki, N. 1984 Lifting mechanism of free jet diffusion flames. 20th Symp. on Combustion, pp. 295–302. The Combustion Institute.
Takahashi, F. & Schmoll, W. J. 1990 Lifting criteria of jet diffusion flames. 23rd Symp. on Combustion, pp. 677–683. The Combustion Institute.
Vatsa, V. N., Werle, M. J. & Verdon, J. M. 1981 Analysis of laminar and turbulent blunt trailing-edge flows. Report R81–914986–5. United Tech. Res. Center, East Hartford, Conn.
Vatsa, V. N., Werle, M. J. & Verdon, J. M. 1982 Viscid-inviscid interaction at laminar and turbulent symmetric trailing edges. AIAA Paper 82-0165.
Vranos, A., Taback, E. D. & Shipman, C. W. 1968 An experimental study of the stability of hydrogen-air diffusion flames. Combust. Flame 12, 253–260.Google Scholar
Williams, F. A. 1985 Combustion Theory, 2nd edn., chapter 3. Benjamin/Cummings.
Yoon, Y., Donbar, J. M. & Driscoll, J. F. 1994 Blowout stability limits of a hydrogen jet flame in a supersonic, heated, coflowing air stream. Combust. Sci. Tech. 97, 137–156.Google Scholar