Hostname: page-component-77c89778f8-5wvtr Total loading time: 0 Render date: 2024-07-19T07:01:15.942Z Has data issue: false hasContentIssue false
  • English
  • Français

Stability of lifted laminar round gas-jet flame

Published online by Cambridge University Press:  21 April 2006

Ö. Savas  and
S. R. Gollahalli
Ö. Savas
Affiliation:
School of Aerospace, Mechanical and Nuclear Engineering, The University of Oklahoma, Norman, Oklahoma 73019, USA
S. R. Gollahalli
Affiliation:
School of Aerospace, Mechanical and Nuclear Engineering, The University of Oklahoma, Norman, Oklahoma 73019, USA
Get access Rights & Permissions [Opens in a new window]

Abstract

The exact solution of the concentration field of jet fluid in a round laminar jet is presented. This analytical solution, which assumes constant kinematic viscosity and molecular diffusivity, establishes the dependence of the concentration field on the Schmidt number. This solution and a kinematic argument are used to calculate the shape of the lifted flame front in a round laminar jet. The observed shape of the lifted laminar propane flame front is compared with the prediction of this formulation. A spatial-stability criterion of the flame is developed and applied to examine the stability of the lifted flame in the flow field of the round laminar jet. The laminar flame blowout height and the corresponding Reynolds number are calculated from the stability criterion. The predictions agree well with the experimental values. The flame blowout Reynolds number of laminar fuel jets of pure fuels discharging from round pipes with fully developed laminar flow is shown to be directly proportional to the pipe diameter. At blowout the fuel concentration in the vicinity of the flame is found to attain a constant value which lies between the lean flammability limit and the fuel concentration at which the laminar flame speed is maximum. This stability criterion is generalized to laminar gas-jet flames of different fuels using three experimentally determined parameters describing their flame speed–concentration characteristics. The general form can account for dilution of fuel jets with inert gases. That flames can be lifted and blown out while they are still laminar is also demonstrated experimentally.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 165 , April 1986 , pp. 297 - 318
Copyright
© 1986 Cambridge University Press

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Andrews, G. E. & Bradley, D. 1972 The burning velocity of methane-air mixtures. Combust. Flame 19, 275–288.Google Scholar
Barr, J. 1953 Diffusion flames. Fourth Symposium (Intl) on Combustion, pp. 765–771.
Batchelor, G. K. 1967 An Introduction to Fluid Dynamics. Cambridge University Press.
Botha, J. P. & Spalding, D. B. 1954 The laminar flame speed of propane/air mixtures with heat extraction from the flame.Proc. R. Soc. Lond. A 22S, 71–96.
Broadwell, J. W., Dahm, W. J. A. & Mungal, M. G. 1985 Blowout of turbulent diffusion flames. Twentieth Symposium (Int.) on Combustion, pp. 303–310.
Egerton, A. & Thabet, S. K. 1952 Flame propagation: the measurement of burning velocities of slow flames and the determination of limits of combustion.Proc. R. Soc. Lond. A 211, 445–480.
Eickhoff, H., Lenze, B. & Leuckel, W. 1985 Experimental investigation on the stabilization mechanism of jet diffusion flames. Twentieth Symposium (Intl) on Combustion, pp. 311–318.
Gibbs, G. J. & Calcote, H. F. 1959 Effect of molecular structure on burning velocity. J. Chem. Engng Data 4, 226–237.Google Scholar
Kanury, A. M. 1977 Introduction to Combustion Phenomena, 3rd edition.Gordon & Breach.
Landau, L. D. 1944 A new exact solution of the Navier-Stokes equations. Dokl. Akad. Sci. URSS 43, 286–288.Google Scholar
Landau, L. D. & Liftshitz, E. M. 1959 Fluid Mechanics. Pergamon.
Peters, N. 1985 Partially premixed diffusion flamelets in non-premixed turbulent combustion. Twentieth Symposium (Int.) on Combustion, pp. 353–360.
Peters, N. & Williams, F. A. 1983 Liftoff characteristics of turbulent jet diffusion flames. AIAA J. 21, 423–429.Google Scholar
Savas, ö. & Gollahalli, S. R. 1986 Flow structure in near-nozzle region of gas jet flames. AIAA J. (in press).
Scholefield, D. A. & Garside, J. E. 1949 The structure and stability of diffusion flames. Third Symposium (Intl) on Combustion, pp. 102–110.
Sivashinsky, G. I. 1983 Instabilities, pattern formation, and turbulence in flames. Ann. Rev. Fluid Mech. 15, 179–199.Google Scholar
Squire, H. B. 1951 The round laminar jet. Q. J. Mech. Appl. Maths 4, 321–329.Google Scholar
Takahashi, F., Mizomoto, M. & Ikai, S. 1983 Laminar burning velocities of hydrogen/oxygen/ inert gas mixtures. In Alternate Energy Sources (ed. T. N. Veziroglu), vol. 5, pp. 447–457. Hemisphere.
Takahashi, F., Mizomoto, M., Ikai, S. & Futaki, N. 1985 Lifting mechanism of free diffusion flames. Twentieth Symposium (Intl) on Combustion, pp. 295–302.