The work presents comparisons of the flame stabilization characteristics of axisymmetric disk and 2D slender bluff-body burner configurations, operating with inlet mixture stratification, under ultralean conditions. A double cavity propane air premixer formed along three concentric disks, supplied with a radial equivalence ratio gradient the afterbody disk recirculation, where the first flame configuration is stabilized. Planar fuel injection along the center plane of the leading face of a slender square cylinder against the approach cross-flow results in a stratified flame configuration stabilized alongside the wake formation region in the second setup. Measurements of velocities, temperatures, and chemiluminescence, local extinction criteria, and large-eddy simulations are employed to examine a range of ultralean and close to extinction flame conditions. The variations of the reacting front disposition within these diverse reacting wake topologies, the effect of the successive suppression of heat release on the near flame region characteristics, and the reemergence of large-scale vortical activity on approach to lean blowoff (LBO) are investigated. The cross-correlation of the performance of these two popular flame holders that are at the opposite ends of current applications might offer helpful insights into more effective control measures for expanding the operational margin of a wider range of stabilization configurations. 1. Introduction The requirements in the design of fuel flexible, low emissions and versatile transportation and power generation systems are placing heavy demands on the development and performance of current combustion devices [1, 2]. As a result the pursuit of new combustion concepts or modes is ongoing and a significant part of the overall design effort is devoted to maintain satisfactory flame stability and efficient emission targets [2, 3]. Over the years lean premixed combustion has gained popularity and has become widely exploited as it addresses some of the above issues over a range of applications [2–4]. However, the anticipated operation of future combustors under increased loads and mixing and burning rates may result in complications such as sensitivity to mixing, low reaction and heat release rates, extinctions, and instabilities [3–5]. Partially premixing and stratifying the reactive mixture is becoming an increasingly widespread strategy for burner design in the effort to expand the stability margin of the lean fully premixed concept and at the same time meet these combined requirements [2, 4–6]. The effective
References
[1]
B. W. Bilger, S. B. Pope, K. N. C. Bray, and J. F. Driscoll, “Paradigms in turbulent combustion research,” Proceedings of the Combustion Institute, vol. 30, no. 1, pp. 21–42, 2005.
[2]
D. Bradley, “Combustion and the design of future engine fuels,” Proceedings of the Institution of Mechanical Engineers C, vol. 223, no. 12, pp. 2751–2765, 2009.
[3]
G. E. Andrews, N. T. Ahmed, R. Phylaktou, and P. King, “Weak extinction in low NOx gas turbine combustion,” in Proceedings of the ASME Turbo Expo, pp. 623–638, June 2009.
[4]
M. Stohr, I. Boxx, C. Carter, et al., “Dynamics of lean blowout of a swirl-stabilized flame in a gas turbine model combustor,” Proceedings of the Combustion Institute, vol. 33, no. 2, pp. 2953–2960, 2011.
[5]
M. S. Sweeney, S. Hochgreb, and R. S. Barlow, “The structure of premixed and stratified low turbulence flames,” Combustion and Flame, vol. 158, no. 5, pp. 935–948, 2011.
[6]
S. G. Tuttle, S. Chaudhuri, K. M. Kopp-Vaughan, et al., “Blowoff dynamics of asymmetrically-fueled, bluffbody flames,” in Proceedings of the 49th AIAA Aerospace Sciences Meeting, AIAA, Orlando, Fla, USA, 2011.
[7]
J. R. Dawson, R. L. Gordon, J. Kariuki, et al., “Visualization of blow-off events in bluff-body stabilized turbulent premixed flames,” Proceedings of the Combustion Institute, vol. 33, no. 1, pp. 1559–1566, 2011.
[8]
Q. Zhang, S. J. Shanbhogue, T. Lieuwen, and J. O'Connor, “Strain characteristics near the flame attachment point in a swirling flow,” Combustion Science and Technology, vol. 183, no. 7, pp. 665–685, 2011.
[9]
C. Duwig, K.-J. Nogenmyr, C.-K. Chan, and M. J. Dunn, “Large eddy simulations of a piloted lean premix jet flame using finite-rate chemistry,” Combustion Theory and Modelling, vol. 15, no. 4, pp. 537–568, 2011.
[10]
E.-S. Cho, S. H. Chung, and T. K. Oh, “Local karlovitz numbers at extinction for various fuels in counterflow premixed flames,” Combustion Science and Technology, vol. 178, no. 9, pp. 1559–1584, 2006.
[11]
P. Koutmos and K. Souflas, “A study of slender bluff body reacting wakes formed by con-current or counter-current fuel injection,” Combustion Science and Technology, vol. 184, no. 9, pp. 1343–1365, 2012.
[12]
K. M. Kopp-Vaughan, T. R. Jensen, B. M. Cetegen, et al., “Analysis of blowoff dynamics from flames with stratified fueling,” Proceedings of the Combustion Institute, vol. 34, no. 1, pp. 1491–1498, 2013.
[13]
C. Z. Xiouris and P. Koutmos, “Fluid dynamics modeling of a stratified disk burner in swirl co-flow,” Applied Thermal Engineering, vol. 35, no. 1, pp. 60–70, 2012.
[14]
O. Colin, F. Ducros, D. Veynante, and T. Poinsot, “A thickened flame model for large eddy simulations of turbulent premixed combustion,” Physics of Fluids, vol. 12, no. 7, pp. 1843–1863, 2000.
[15]
G. Wang, M. Boileau, and D. Veynante, “Implementation of a dynamic thickened flame model for large eddy simulations of turbulent premixed combustion,” Combustion and Flame, vol. 158, no. 11, pp. 2199–2213, 2011.
[16]
P. Koutmos, G. Paterakis, E. Dogkas, and C. H. Karagiannaki, “The impact of variable inlet mixture stratification on flame topology and emissions performance of a premixer/swirl burner configuration,” Journal of Combustion, vol. 2012, Article ID 374089, 12 pages, 2012.
[17]
R. R. Erickson and M. C. Soteriou, “The influence of reactant temperature on the dynamics of bluff body stabilized premixed flames,” Combustion and Flame, vol. 158, no. 12, pp. 2441–2457, 2011.
[18]
J. J. Miau, T. S. Leu, T. W. Liu, and J. H. Chou, “On vortex shedding behind a circular disk,” Experiments in Fluids, vol. 23, no. 3, pp. 225–233, 1997.
[19]
A. G. Bakrozis, D. D. Papailiou, and P. Koutmos, “A study of the turbulent structure of a two-dimensional diffusion flame formed behind a slender bluff-body,” Combustion and Flame, vol. 119, no. 3, pp. 291–306, 1999.
[20]
D. Trimis, Verbrennungsvorgange in Porosen Inerten Medien, BEV 95.5, ESYTEC, Elangen, Germany, 1996.
[21]
C. Dasch, “One-dimensional tomography: a comparison of Abel, onion-peeling, and filtered back-projection methods,” Applied Optics, vol. 31, no. 8, pp. 1146–1152, 1992.
[22]
ANSYS Fluent, Release 12.0, Theory Guide, ANSYS, 2009.
[23]
L. Gicquel, G. Staffelbach, and T. Poinsot, “Large Eddy Simulations of gaseous flames in gas turbine combustion chambers,” Progress in Energy and Combustion Science, vol. 38, no. 6, pp. 782–817, 2012.
[24]
A. Briones and B. Sekar, Effect of Von Kármán Vortex Shedding on Regular and Open-Slit V-Gutter Stabilized Turbulent Premixed Flames, Spring Technical Meeting of the Central States Section of the Combustion Institute, University of Dayton, Air Force Research Laboratory Dayton, 2012.
