Investigation of Scalar Filtered Density Function in Turbulent Partially Premixed Flames

Abstract

The filtered mass density function (FMDF) of mixture fraction and other filtered variables used in large-eddy simulation of turbulent combustion are studied using measurement data obtained in turbulent partially premixed methane/air (Sandia) flames. For SGS scalar variance small compared to its mean, the FMDF is not far from Gaussian and the SGS scalar is well mixed. For large SGS variance, however, the FMDF becomes bimodal and the conditionally filtered scalar dissipation is bell-shaped, indicating the existence of a diffusion (dissipation) layer structure, which is similar to the mixture fraction profile in the counter-flow model for laminar flamelets. The conditionally filtered temperature near the stoichiometric mixture fraction decreases progressively with increasing SGS scalar variance. Furthermore, local extinction events appear to occur mostly when the SGS scalar variance is large, suggesting the possibility of flamelet extinction. The results suggest that the mixing regimes and the associated mixture fraction structure could potentially have strong influences on the combustion regime and extinction/reignition in turbulent nonpremixed flames.

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Document Details

Document Type
Technical Report
Publication Date
Jun 01, 2006
Accession Number
ADP023649

Entities

People

  • Chenning Tong

Organizations

  • Clemson University

Tags

Communities of Interest

  • Materials and Manufacturing Processes

DTIC Thesaurus Topics

  • Air Force
  • Boltzmann Equation
  • Chemical Reactions
  • Combustion
  • Diffusion
  • Dissipation
  • Equations
  • Experimental Data
  • Extinction
  • Filters
  • Flames
  • Gaussian Distributions
  • Jet Flames
  • Large Eddy Simulation
  • Measurement
  • Mechanical Engineering
  • Military Research

Fields of Study

  • Physics

Readers

  • Combustion science or combustion engineering.
  • Computational Fluid Dynamics (CFD)
  • Statistical inference.