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Large Eddy Simulation and Experiments of Stratified Lean Premixed Methane/Air Turbulent Flames

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Summary, in English

This paper presents a joint large eddy simulation and laser diagnostic investigation of premixed turbulent low swirl flames. A lean premixed methane/air mixture, of the equivalence ratio 0.60-0.66, is injected from a 50 mm diameter low swirl burner to a low speed co-flowing air at room temperature and pressure. The level-set G-equation is employed to simulate the inner layer flame front. Flamelet chemistry is used to determine the flame properties in the reactive zones. Mixing and heat transfer in the post-flame zone down-stream are modeled using transport equations. In addition to large eddy simulation, simultaneous 2-D laser induced fluorescence of OH and 2-D particle image velocimetry are used to characterize the basic flame structure. Laser Doppler velocimetry is employed to further analyze the flow velocity along the central axis above the burner, and 2-D filtered Rayleigh scattering is used to measure the temperature field in the lower part of the flame. A bowl-shaped, highly wrinkled turbulent flame is stabilized at a position about one-half diameter above the burner. The flame consists of two distinct parts; around the burner axis, a premixed flame with uniform mixture fraction is stabilized in the low speed flow region induced by the inflow swirl; off the axis of the burner, a stratified lean premixed flame is found in the shear layer of the flow field. Flame holes (local extinction) owing to overly lean mixtures are observed in the off-axis lean stratified part of the flame. A unified level-set G-equation is developed to model the flame holes. The basic flow and flame structure from the model simulations are compared to the laser diagnostic measurements; the height of flame stabilization (lift-off height), the mean temperature profile, and the mean axial and radial velocity components together with rms velocity components are in fairly good agreement with measurement data. © 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Publishing year

2007

Language

English

Pages

1467-1475

Publication/Series

Proceedings of the Combustion Institute

Volume

31

Issue

1

Document type

Journal article

Publisher

Elsevier

Topic

  • Atom and Molecular Physics and Optics
  • Fluid Mechanics and Acoustics

Keywords

  • Equivalence ratios
  • Radial velocity
  • Premixed turbulent low swirl flames
  • Velocity components

Conference name

31st International Symposium on Combustion

Conference date

2006-08-05 - 2006-08-11

Conference place

Heidelberg, Germany

Status

Published

ISBN/ISSN/Other

  • ISSN: 1540-7489