M.O. Vigueras-Zuñiga1, A. Valera-Medina*2, N. Syred3
1 Facultad de Ingeniería, Universidad Veracruzana, Veracruz, Veracruz, México.
2 Centro de Tecnología Avanzada, CIATEQ A.C. Queretaro, Qro, México *agustin.valera@ciateq.mx.
3 School of Engineering, Gas Turbine Research Centre, Cardiff University, Wales, United Kingdom.
Abstract
]]> Large scale coherent structures play an important role in the behavior of the combustion regime inside any type of combustor stabilized by swirl, with special impact on factors such as flame stability, blow off, emissions and the occurrence of thermo-acoustic oscillations. Lean premixed combustion is widely used and is known to impact many of these factors, causing complex interrelationships with any coherent structure formed. Despite the extensive experimentation in this matter, the above phenomena are poorly understood. Numerical simulations have been used to try to explain the development of different regimes, but their extremely complex nature and lack of time dependent validation show varied and debatable results. The precessing vortex core (PVC) is a well-known coherent structure whose development, intensity and occurrence has not been well documented. This paper thus adopts an experimental approach to characterize the PVC in a simple swirl burner under combustion conditions so as to reveal the effects of swirl and other variables on the latter. Aided by a high speed photography (HSP) system, the recognition and extent of several different types of PVCs were observed and discussed.Keywords: swirling flows, PVC, high speed photography.
Resumen
Las estructuras coherentes de larga escala juegan un importante papel en el comportamiento de la combustión dentro de cualquier quemador estabilizado por arremolinamiento, impactando especialmente en factores como la estabilidad y extinción de la flama, emisiones y la aparición de oscilaciones termo-acústicas. La combustión en estado pobre es ampliamente utilizada y es sabido que impacta también en estos factores, causando una compleja interrelación con las estructuras que se forman. A pesar del extensivo trabajo experimental en el campo, el fenómeno antes mencionado no es completamente entendido. Se han utilizado simulaciones numéricas para explicar el desarrollo de diferentes regímenes, pero su extremamente compleja naturaleza y la falta de validación temporal han llevado a grandes debates en el campo. El centro de vórtice precesor (CVP) es una estructura coherente bien conocida cuyo desarrollo, intensidad y ocurrencia no se han documentado completamente. Por ello, este artículo adopta una aproximación experimental para caracterizar al CVP en un quemador sencillo bajo condiciones de combustión que revelen el efecto de arremolinamiento así como otras variables. Se llevó a cabo el reconocimiento de muchos diferentes tipos de CVP con la ayuda de un sistema de fotografía de alta velocidad.
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References
[1] A.K. Gupta et al., "Swirl Flows", Tunbridge Wells, Abacus Press, U.K., 1984. [ Links ]
[2] N. Syred and J.M. Beer, "Combustion in Swirling Flow: A Review", Combust Flame, vol. 23, pp.143-201, 1974. [ Links ]
[3] N. Syred, "A Review of Oscillation Mechanisms and the role of the Precessing Vortex Core (PVC) in Swirl Combustion Systems", Prog Energy Combust Sci, vol. 32, issue 2, pp. 93-161, 2006. [ Links ]
[4] K. Vanoverberghe, "Flow, Turbulence and Combustion of Premixed Swirling Jet Flame", PhD Thesis, Faculty of Engineering, Katholieke Universiteit Leuven, Belgium, 2004. [ Links ]
[5] A. Coghe et al., "Recirculation phenomena in a natural gas swirl combustor", Exp Thermal Fluid Sci, vol. 28, pp. 709-714, 2004. [ Links ]
[6] A. Valera-Medina, "Coherent Structures and their effects on Processes occurring in Swirl combustors", PhD Thesis, Cardiff University, Wales, U.K., 2009. [ Links ]
[7] C. Paschereit and E. Gutmark, "Enhanced Stability and Reduced Emissions in an Elliptic Swirl-Stabilized Burner", J. AIAA, vol. 46, no. 5, pp. 1063-1071, 2008. [ Links ]
[8] S. Kuhn et al, "Influence in wavy surfaces on coherent structures in a turbulent flow", Exp Fluids, vol. 43, no 2-3, pp. 20-28, 2006. [ Links ]
[9] T. Claypole and N. Syred, "The Effect of Swirl Burner Aerodynamics on NOx Formation", Proc. 18th International Symposium. on Combustion, The Combustion Institute, Pittsburgh, Pa, USA, pp.81-90, 1981. [ Links ]
[10] D. Froud et al, "Phase Averaging of the Precessing Vortex Core in a Swirl Burner under Piloted and Premixed Combustion Conditions", Combust Flame, vol. 100, no. 3, pp. 407-412, 1995. [ Links ]
[11] T. Sarpkaya, "On Stationary and travelling Vortex Breakdown", J. Fluid Mech, vol. 45, no. 3, pp.545-559, 1971. [ Links ]
[12] O. Lucca-Negro and T. O'Doherty, "Vortex Breakdown: A Review", Prog Energy Combust Sci, vol. 27, no. 4, pp. 431-481, 2001. [ Links ]
[13] D. Bradley et al, "Premixed turbulent flame instability and no formation in a Lean Burn Swirl Burner", Combust Flame, vol. 115, pp.515-538, 1998. [ Links ]
[14] S. Lee et al, "An experimental estimation of mean reaction rate and flame structure during combustion instability in a lean premixed gas turbine combustor", Proc Combust Inst, vol. 28, pp. 775-782, 2000. [ Links ]
[15] T. O'Doherty and R. Gardner, "Turbulent Length Scales in an Isothermal Swirling Flow", The 8th Symp Fluid Control, Measurement and Visualization, Japan, pp. 6, 2005. [ Links ]
[16] Y. Bouremel et al, "Vorticity and Strain Dynamics for Vortex Ring Mixing Process", Proc 14th Int Symp on Applications of Laser Techniques to Fluid Mechanics, Lisbon, Portugal, 2008. [ Links ]
[17] W. Malalasekera et al, "LES of Recirculation and Vortex Breakdown in Swirling Flames", Combust Sci Tech, vol. 180, pp. 809-832, 2008. [ Links ]
[18] Y. Lafay et al, "Experimental study of biogas combustion using a gas turbine configuration", Exp Fluids, vol. 43, no 2-3, pp. 112-128, 2006. [ Links ]
[19] T. Lieuwen and V. Yang, "Combustion Instabilities in Gas Turbine Engines", AIAA, Progress in Astronautics and Aeronautics, vol. 210, U.S.A, 2005. [ Links ]
[20] Y. Huang and V. Yang, "Modelling and Control of Combustion Dynamics in Lean Premixed Swirl Stabilized Combustors", Proc 6th Symp Smart Control of Turbulence. Japan, pp. 1-21, 2005. [ Links ]
[21] A. Valera-Medina et al, "Visualization of Isothermal Large Coherent Structures in a Swirl Burner", Combust Flame, vol. 156, issue 9, pp. 1723-1734, 2009. [ Links ]
[22] Y. Al-Abdeli and A. Masri, "Turbulent swirling natural gas flames: stability characteristics, unsteady behaviour and vortex breakdown", Combust Sci Tech, vol. 179, pp. 207-225, 2007. [ Links ]
[23] A. Sadiki et al, "Unsteady Methods (URANS and LES) for simulation of combustion systems", Int J Thermal Sci, vol. 45, issue 8, pp. 760-773, 2006. [ Links ]
[24] M. Freitag et al, "Mixing analysis of a swirling recirculating flow using DNS and experimental data", Int J Heat Fluid Flow, vol. 27, issue 4, pp. 636-643, 2006. [ Links ]
[25] L. Selle et al, "Joint use of compressible large-eddy simulation and Helmholtz solvers for the analysis of rotating modes in an industrial swirled burner", Combust Flame, vol. 145, issue 1-2, pp. 194-205, 2006. [ Links ]
[26] P. Jochmann, "Numerical simulation of a precessing vortex breakdown", Int J Heat Fluid Flow, vol. 27, pp. 192-203, 2006. [ Links ]
[27] S. Roux et al, "Studies of mean and unsteady flow in a swirled combustor using experiments, acoustic analysis and large eddy simulations", Combust Flame, vol. 141, pp. 40-54, 2005. [ Links ]
[28] P. Davidson, "Turbulence: an introduction for Scientists and Engineers", Oxford University Press, U.K., pp. 678, 2004. [ Links ]
[29] S. Pope, "Turbulent Flows", Cambridge University Press, U.K., pp. 806, 2000. [ Links ]
[30] A. Valera-Medina et al, "Characterization of Large Coherent Structures in a Swirl Burner", AIAA Aerosp Sci Meeting, Reno, Nevada, AIAA 2008-1019, 2008. [ Links ]
[31] S. Aleseenko et al, "Helical vortex in swirl flow", J Fluid Mech, vol. 382, pp.195-243, 1999. [ Links ]
[32] M. Vaniershot, "Fluid Mechanics and Control of Annular Jets with and without Swirl", PhD Thesis, Faculty of Engineering, Katholieke Universiteit Leuven, Belgium, 2007. [ Links ]
[33] J. Dawson, "An investigation into naturally excited Helmholtz oscillations in a swirl burner/furnace system", PhD Thesis, Cardiff University, Wales, UK, 2000. [ Links ]
[34] E. Cala et al, "Coherent Structures in unsteady swirling jet flow", Exp Fluids, vol. 40, pp. 267-276, 2006. [ Links ]
[35] S. Shtork et al, "On the Identification of helical instabilities in a reacting swirling flow", Fuel, vol. 87, pp. 2314-2321, 2008. [ Links ]
[36] A. Valera-Medina et al, "Central Recirculation Zone Analysis in an Unconfined Tangential Swirl Burner with Varying Degrees of Premixing", Exp Fluids, 2010, doi: 10.1007/s00348-010-1017-7. [ Links ]
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