Characterization of large coherent structures in a swirl burner under combustion conditions

Dry Low NOx combustors based on the use of Lean Pre-mixtures and Swirling Flows are widely used in gas turbine combustors to produce systems with low emissions, although the efficiency of reducing emissions is dependant on the techniques used for premixing. Swirling flows are recognized as one of the best systems for stabilizing high intensity flames giving reduced maintenance, increase of turbulent flame speed, wide stability limits and ability to produce low emissions. However, most practical swirling flows are highly complex, three dimensional and time dependant in nature and contain complex coherent structures which are essential to the flame stabilization process. Even though the study of these types of flows has been extensive for several decades , some of the fundamental mechanisms are still barely understood owing to their complexity. Numerical simulations have also tried to explain the development of different regimes, but the extremely complex nature of the former has shown a variety of results whose lack of time dependant validation leaves the results open to question. Due to the high complexity of these flows, parameters such as Re, S, φ and geometry play a crucial role in the development of these structures, interrelation that has been barely studied. This paper thus adopts an experimental approach to characterize large coherent structures in swirl burners under combustion conditions so as to reveal the effects of swirl, Re and φ in a number of geometries. Aided by different techniques such as High Speed Photography (HSP), CH* Photo Chemiluminescence (CH* CL) and Particle Image Velocimetry (PIV), the recognition of several structures was achieved in a 100 kW Swirl Burner model. Several varied, interacting, structures developed in the field as a consequence of the configurations used.

[1]  Jochen Ströhle,et al.  An evaluation of detailed reaction mechanisms for hydrogen combustion under gas turbine conditions , 2007 .

[2]  Assaad R. Masri,et al.  TURBULENT SWIRLING NATURAL GAS FLAMES: STABILITY CHARACTERISTICS, UNSTEADY BEHAVIOR AND VORTEX BREAKDOWN , 2007 .

[3]  Koen Vanoverberghe,et al.  Flow, turbulence and combustion of premixed swirling jet flames , 2004 .

[4]  E. Serre,et al.  Vortex breakdown in a cylinder with a rotating bottom and a flat stress-free surface , 2007 .

[5]  Salah S. Ibrahim,et al.  LES of Recirculation and Vortex Breakdown in Swirling Flames , 2008 .

[6]  M. J. Scott,et al.  Premixed turbulent flame instability and NO formation in a lean-burn swirl burner , 1998 .

[7]  David F. Fletcher,et al.  Simulation of Turbulent Swirl Flow in an Axisymmetric Sudden Expansion , 2001 .

[8]  Johannes Janicka,et al.  Unsteady methods (URANS and LES) for simulation of combustion systems , 2006 .

[9]  A. Mestre,et al.  Combustion in swirling flow , 1973 .

[10]  Maarten Vanierschot,et al.  Fluid mechanics and control of annular jets with and without swirl , 2007 .

[11]  János M. Beér,et al.  Combustion in swirling flows: A review , 1974 .

[12]  Vigor Yang,et al.  Effect of swirl on combustion dynamics in a lean-premixed swirl-stabilized combustor , 2005 .

[13]  Rainer Koch,et al.  Numerical simulation of a precessing vortex breakdown , 2006 .

[14]  Ivor Day,et al.  Passive Control of Combustion Instability in a Low Emissions Aeroderivative Gas Turbine , 2004 .

[15]  F. Güthe,et al.  Thermoacoustically driven flame motion and heat release variation in a swirl-stabilized gas turbine burner investigated by LIF and chemiluminescence , 2008 .

[16]  Christian Oliver Paschereit,et al.  Enhanced Stability and Reduced Emissions in an Elliptic Swirl-Stabilized Burner , 2008 .

[17]  M. Stöhr,et al.  Simultaneous OH-PLIF and PIV measurements in a gas turbine model combustor , 2008 .

[18]  C. A. Berg.  Conservation in industry. , 1974, Science.

[19]  F. Nicoud,et al.  Joint use of compressible large-eddy simulation and Helmholtz solvers for the analysis of rotating modes in an industrial swirled burner , 2006 .

[20]  N. Syred.  A review of oscillation mechanisms and the role of the precessing vortex core (PVC) in swirl combustion systems , 2006 .

[21]  T. Poinsot,et al.  Studies of mean and unsteady flow in a swirled combustor using experiments, acoustic analysis, and large eddy simulations , 2005 .

[22]  Johannes Janicka,et al.  MIXING ANALYSIS OF A SWIRLING RECIRCULATING FLOW USING DNS AND EXPERIMENTAL DATA , 2006, Proceeding of Fourth International Symposium on Turbulence and Shear Flow Phenomena.

[23]  Timothy O'Doherty,et al.  Phase averaging of the precessing vortex core in a swirl burner under piloted and premixed combustion conditions , 1995 .