Large eddy simulation of piloting effects on turbulent swirling flames

Abstract Pilot flames, created by additional injectors of pure fuel, are often used in turbulent burners to enhance flame stabilization and reduce combustion instabilities. The exact mechanisms through which these additional rich zones modify the flame anchoring location and the combustion dynamics are often difficult to identify, especially when they include unsteady hydrodynamic motion. This study presents Large Eddy Simulations (LES) of the reacting flow within a large-scale gas turbine burner for two different cases of piloting, where either 2 or 6% of the total methane used in the burner is injected through additional pilot flame lines. For each case, LES shows how the pilot fuel injection affects both flame stabilization and flame stability. The 6% case leads to a stable flame and limited hydrodynamic perturbations in the initial flame zone. The 2% case is less stable, with a small-lift-off of the flame and a Precessing Vortex Core (PVC) in the cold stabilization zone. This PVC traps some of the lean cold gases issuing from the pilot passage stream, changes the flame stabilization point and induces instability.

[1]  F. Ducros,et al.  A thickened flame model for large eddy simulations of turbulent premixed combustion , 2000 .

[2]  R. Koch,et al.  Compressible large eddy simulation of turbulent combustion in complex geometry on unstructured meshes , 2004 .

[3]  Thierry Poinsot,et al.  Dynamics and mixing in jet/vortex interactions , 2003 .

[4]  P. Moin,et al.  Approximate Wall Boundary Conditions in the Large-Eddy Simulation of High Reynolds Number Flow , 2000 .

[5]  T. Takeno,et al.  A numerical analysis of the structure of a turbulent hydrogen jet lifted flame , 2002 .

[6]  Dieter Vortmeyer,et al.  Active instability control with direct-drive servo valves in liquid-fueled combustion systems , 1996 .

[7]  T. O’Doherty,et al.  Vortex breakdown: a review , 2001 .

[8]  F. Lacas,et al.  Large eddy simulation and experimental study of flashback and blow-off in a lean partially premixed swirled burner , 2004 .

[9]  S. Menon,et al.  LES of spray combustion in swirling flows , 2002 .

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

[11]  Thierry Poinsot,et al.  Large eddy simulation predictions of mixing enhancement for jets in cross-flows , 2004 .

[12]  T. Poinsot,et al.  Theoretical and numerical combustion , 2001 .

[13]  J. Chomaz,et al.  Experimental study of vortex breakdown in swirling jets , 1998, Journal of Fluid Mechanics.

[14]  Thierry Poinsot,et al.  Active control : an investigation method for combustion instabilities , 1992 .

[15]  Luc Vervisch,et al.  Three facets of turbulent combustion modelling: DNS of premixed V-flame, LES of lifted nonpremixed flame and RANS of jet-flame , 2004 .

[16]  S. Candel,et al.  A review of active control of combustion instabilities , 1993 .

[17]  Franck Nicoud,et al.  Large-eddy simulation and acoustic analysis of a swirled staged turbulent combustor , 2006 .

[18]  M. G. Mungal,et al.  Instantaneous flame-stabilization velocities in lifted-jet diffusion flames , 1997 .

[19]  H. Pitsch,et al.  Large-eddy simulation of a turbulent piloted methane/air diffusion flame (Sandia flame D) , 2000 .

[20]  J. Smagorinsky,et al.  GENERAL CIRCULATION EXPERIMENTS WITH THE PRIMITIVE EQUATIONS , 1963 .

[21]  Thomas Sattelmayer,et al.  Instability of a Premix Burner With Nonmonotonic Pressure Drop Characteristic , 2003 .

[22]  Thierry Poinsot,et al.  Numerical methods for unsteady compressible multi-component reacting flows on fixed and moving grids , 2005 .

[23]  Franck Nicoud,et al.  Actual impedance of nonreflecting Boundary conditions: Implications for computation of resonators , 2004 .

[24]  T. Poinsot.  Boundary conditions for direct simulations of compressible viscous flows , 1992 .

[25]  Denis Veynante,et al.  LES of Chemical and Acoustic Forcing of a Premixed Dump Combustor , 2000 .