Hostname: page-component-cd9895bd7-gbm5v Total loading time: 0 Render date: 2024-12-26T07:22:30.609Z Has data issue: false hasContentIssue false
  • English
  • Français

Investigation of an excited jet diffusion flame at elevated pressure

Published online by Cambridge University Press:  26 April 2006

Anthony W. Strawa  and
Brian J. Cantwell
Anthony W. Strawa
Affiliation:
NASA Ames Research Center, Moffett Field, CA 94035, USA.
Brian J. Cantwell
Affiliation:
Department of Aeronautics and Astronautics, Stanford University, Stanford, CA 94305, USA.
Get access Rights & Permissions [Opens in a new window]

Abstract

Experiments have been carried out with the objective of studying the relationship between flow structure, flow excitation and the reaction process in the near field of a low-speed coflowing jet diffusion flame. The effect of axial forcing and increasing pressure on the structure and controllability of the flame has been studied in an attempt to elucidate some of the underlying mechanisms of control. The experiments were conducted in a variable-pressure flow facility which permits the study of reacting flows at pressures ranging from 10 to 1000 kPa (0.1 to 10 atm.). The flame was excited by adding a small-amplitude, periodic fluctuation to the central fuel jet exit velocity. The flow was visualized using an optical scheme which superimposes the luminous image of the flame on its schlieren image, giving a useful picture of the relationship between the luminous soot-laden core flow and the edge of the surrounding hot-gas envelope. Phase-conditioned velocity measurements were made with a one-component laser Doppler anemometer. The excitation frequency was varied, and it was found that a narrow band of frequencies exists in which several of the instabilities of the flow seem to be in coincidence, causing the flame to break up periodically into a series of distinct eddies. Hereafter this will be called the strongly coupled state. Maps of the one-dimensional velocity vector field, viewed in a frame of reference convecting with the large eddies, are used to study the topology of the flow. When the excitation frequency lies above the strongly coupled range, the flow pattern is found to contain stagnation points which straddle the axis of the jet. When the excitation frequency is reduced to a point where strong coupling occurs the stagnation points move onto the axis promoting breakup of the flame. As the pressure is increased, the relative role of diffusion is decreased and the flame becomes highly three-dimensional. In the strongly coupled state, the flow continues to be very periodic, even to the extent that much of the three-dimensional structure is repeatable from cycle to cycle.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 200 , March 1989 , pp. 309 - 336
Copyright
© 1989 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

Ballantyne, A. & Bray, K. N. C. 1977 Investigations into the structure of jet diffusion flames. Sixteenth Symp. (Intl) on Combustion, pp. 777–787. The Combustion Institute.
Baker, H. A. & Liang, D., 1983 Soot emission, thermal radiation and laminar instabilities of acetylene diffusion flames. Combust. Flame 52, 247–256.Google Scholar
Chamberlin, D. S. & Rose, A., 1928 The flicker of luminous flames. Indust. Engng Chem. 20, 1013–1016.Google Scholar
Chapman, G. T.: 1986 Topological classification of flow separation on three-dimensional bodies. AIAA paper 86–0485.Google Scholar
Chigier, N. A. & Yule, A. J., 1979 The physical structure of turbulent flames. AIAA paper 79–0217, pp. 1–8.Google Scholar
Dibble, R. W., Kollmann, W. & Schefer, R. W., 1984 Measurements and predictions of scalar dissipation in turbulent jet flames. Twentieth Symp. (Intl) on Combustion, pp. 345–352. The Combustion Institute, Ann Arbor, Mich.
Favre, A., Gaviglio, J. & Dumas, R., 1967 Structure of velocity space-time correlations in a boundary layer. Phys. Fluids 10, S138–S145.Google Scholar
Flower, W. L. & Bowman, C. T., 1985 Twentieth Symp. (Intl) on Combustion, pp. 1035–1044. The Combustion Institute. Ann Arbor, Mich.
Friedlander, S. K.: 1977 Smoke, Dust and Haze. Wiley.
Grant, A. J. & Jones, J. M., 1975 Low frequency diffusion flame osscilations. Combust. Flame 25, 153–160.Google Scholar
Karagozian, A. R. & Manda, B. V. S. 1986 Flame structure and fuel consumption in the field of a vortex pair. Combust. Sci. Tech. 49, 185–200.Google Scholar
Lepicovsky, J.: 1986 Laser velocimeter measurements of large-scale structures in a tone-excited jet. AIAA J. 27–31.Google Scholar
Lewis, G. S., Cantwell, B. J. & Lecuona, A., 1987 The use of particle tracking to obtain planar velocity measurements in an unsteady laminar diffusion flame. Paper 87–35, meeting of Western States Section/The Combustion Institute, Provo, Utah.Google Scholar
Lewis, G. S., Cantwell, B. J., Vandsburger, U. & Bowman, C. T., 1988 An investigation of the interaction of a laminar non-premixed flame with an unsteady vortex. Paper accepted for the Twenty Second (Intl) Symp, on Combustion. The Combustion Institute, Pittsburgh.
McArragher, J. S. & Tan, K. J., 1972 Soot formation at high pressure: a literature review. Combust. Sci. Tech. 5, 257–261.Google Scholar
Perry, A. E. & Chong, M. S., 1987 A description of eddying motions and flow patterns using critical-point concepts. Ann. Rev. Fluid Mech. 19, 125–155.Google Scholar
Perry, A. E. & Lim, T. T., 1978 Coherent structures in coflowing jets and wakes. J. Fluid Mech. 88, 451–464.Google Scholar
Perry, A. E., Lim, T. T. & Chong, M. S., 1980 The instantaneous velocity fields of coherent structures in coflowing jets and wakes. J. Fluid Mech. 101, 243–256.Google Scholar
Rayleigh, Lord., 1877 The Theory of Sound, vol. 11, pp. 227–228. [Dover, New York, 1977.]
Roper, F. G.: 1977 The prediction of laminar jet diffusion flame sizes. Part 1. Theoretical model. Combust. Flame 29, 219–226.Google Scholar
Roquemore, W. M., Tankin, R. S., Chiu, H. H. & Lottes, S. A., 1984 In ASME AMD – Vol. 66: Experimental Measurements and Techniques in Turbulent Reactive and Non-Reactive Flows (ed. R. M. C. So, J. H. Whitelaw & M. Lapp), pp. 159–175.
Strawa, A. W.: 1986 An experimental investigation of the structure of an acoustically excited diffusion flame. Ph.D. thesis, Stanford University. SUDAAR 558.
Strawa, A. W. & Cantwell, B. J., 1985 Visualization of the structure of a pulsed methane air diffusion flame. Phys. Fluids 28, 2317–2320.Google Scholar
Subbarao, E. R.: 1987 An experimental investigation of the effects of Reynolds number and Richardson number on the structure of a co-flowing buoyant jet. Ph.D. thesis, Stanford University. SUDAAR 563.
Yule, A. J., Chigier, N. A., Ralph, S., Boulderstone, R. & Ventrura, J., 1980 Combustion-transition interactions in a jet flame. AIAA J. 19, 752–760.Google Scholar