Stability characteristics and flowfields of turbulent non-premixed swirling flames. (English) Zbl 1068.80502
Summary: A simple, yet representative, burner geometry is used for the investigation of highly swirling turbulent unconfined, non-premixed, flames of natural gas. The burner configuration comprises a ceramic faced bluff-body with a central fuel jet. The bluff-body is surrounded by an annulus that delivers a swirling primary flow of air. The entire burner assembly is housed in a wind tunnel providing a secondary co-flowing stream of air. This hybrid bluff-body/swirl burner configuration stabilizes complex turbulent flames not unlike those found in practical combustors, yet is amenable to modelling because of its well-defined boundary conditions. Full stability characteristics including blow-off limits and comprehensive maps of flame shapes are presented for swirling flames of three different fuel mixtures: compressed natural gas (CNG), CNG-air (1:2 by volume) and CNG-H\(_2\) (1:1 by volume). It is found that with increased fuel flow, flame blow-off mode may change with swirl number, S\(_{\text g}\). At low swirl, the flame remains stable at the base but blows off in the neck region further downstream. At higher swirl numbers, the flames peel off completely from the burner’s base. Swirling CNG-air flames are distinct in that they only undergo base blow-off. In the low range of swirl number, increasing S\(_{\text g}\) causes limited improvement in the blow-off limits of the flames investigated and (for a few cases) can even lead to some deterioration over a small intermediate range of S\(_{\text g}\). It is only above a certain threshold of swirl that significant improvements in blow-off limits appear. Six flames are selected for further detailed flowfield and composition measurements and these differ in the combination of swirl number, primary axial velocity through the annulus, U\(_{\text s}\), and bulk fuel jet velocity, U\(_{\text j}\). Only velocity field measurements are presented in this paper. A number of flow features are resolved in these flames, which resemble those already associated with non-reacting swirling flows of equivalent swirl obtained with the present burner configuration. Additionally, asymmetric flowfields inherent to some flames are revealed where the fluidic centreline of the flow (defined in the two-dimensional (U-W velocity pair) velocity field by the = 0 tangential velocity contour), meanders strongly on either side of the geometric centreline downstream by about one bluff-body diameter. Flow structures revealed by the velocity data are correlated to flame shapes to yield a better understanding of how the velocity field influences the flames physical characteristics.
MSC:
| 80A25 | Combustion |
References:
| [1] | Feikema D, Combust. Flame 86 pp 347– (1991) |
| [2] | Chen R-H, Proc. Combust. Inst. 22 pp 531– (1988) |
| [3] | Tangirala V, Combust. Sci. Technol. 60 pp 143– (1988) |
| [4] | Liley D G, AIAA J. 15 pp 1063– (1977) |
| [5] | Chen R-H, Combust. Sci Technol. 110-111 pp 443– (1995) |
| [6] | The International Flame Research Foundation |
| [7] | Leuckel W, J. Inst. Fuel 49 pp 103– (1976) |
| [8] | Wu H L, J. Inst. Fuel 49 pp 144– (1976) |
| [9] | Fricker N, J. Inst. Fuel 49 pp 152– (1976) |
| [10] | Syred N, Combust. Flame 23 pp 143– (1974) |
| [11] | Farokhi S, AIAA J. 27 pp 700– (1989) |
| [12] | Milosavljevic V D, Combust. Flame 80 pp 196– (1990) |
| [13] | Froud D, Combust. Flame 100 pp 407– (1995) |
| [14] | DOI: 10.1017/S002211209800202X · Zbl 0925.76017 · doi:10.1017/S002211209800202X |
| [15] | Al-Abdeli Y M, Combust. Sci. Technol. (2003) |
| [16] | Escudier M P, J. Fluid Mech. 115 pp 105– (1982) |
| [17] | Chigier N A, Trans. ASME-J. Basic Eng. 86 pp 788– (1964) |
| [18] | International Workshop on Measurement and Computation of Turbulent Nonpremixed Flames |
| [19] | Tsuji H, Prog. Energy Combust. Sci. 8 pp 93– (1982) |
| [20] | Masri A R, Prog. Energy Combust. Sci. 22 pp 307– (1996) |
| [21] | Lindstedt R P, Proc. Combust. Inst. 28 pp 149– (2000) |
| [22] | Tang Q, Proc. Combust. Inst. 28 pp 133– (2000) |
| [23] | Masri A R, Combust. Flame |
| [24] | Masri A R |
| [25] | Al-Abdeli Y M, Exp. Therm. Fluid Sci. 27 pp 655– (2003) |
| [26] | Sheen H J, Exp. Therm. Fluid Sci. 12 pp 444– (1996) |
| [27] | Billiant P, J. Fluid Mech. 376 pp 183– (1998) |
| [28] | Kalt P A M, Proc. Combust. Inst. 29 pp 1913– (2002) |
| [29] | Masri A R, Proc. Combust. Inst. 20 pp 319– (1984) |
| [30] | Edwards R V, J. Fluids Eng. 109 pp 89– |
| [31] | Guo B Fletcher D F Marquez G Al-Abdeli Y M Starner S H Masri A R, 2003 Australian Symp. on Combustion and the 8th Australian Flame Days (2003) |
| [32] | Al-Abdeli Y M |
| [33] | Dibble R W, Exp. Fluids 5 pp 103– (1987) |
| [34] | Esquiva-Dano I, Combust. Flame 127 pp 2167– (2001) |
| [35] | Gupta A K, Swirl Flows (1984) |
| [36] | Escudier M P, AIAA J. 23 pp 111– (1985) |
| [37] | Marquez G R (2003) |
| [38] | Landenfeld T Kremer A Hassel E P Janicka, 11th Symp. on Turbulent Shear Flows pp 18/1– (1997) |
| [39] | Weber R, Int. J. Heat Fluid Flow 11 pp 225– (1990) |
| [40] | Weber R, Prog. Energy Combust. Sci. 18 pp 349– (1992) |
| [41] | Chigier N A, Trans. ASME-J. Appl. Mech. 34 pp 443– (1967) |
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