Study of Laminar Flame 2-D Scalar Values at Various Fuel to Air Ratios Using an Imaging Fourier-Transform Spectrometer and 2-D CFD Analysis

Author

Andrew J. Westman

Date of Award

3-21-2013

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Engineering Physics

First Advisor

Kevin C. Gross, PhD.

Abstract

This work furthers an ongoing effort to develop imaging Fourier-transform spectrometry (IFTS) for combustion diagnostics and to validate reactive-flow computational fluid dynamics (CFD) predictions. An ideal, laminar flame produced by an ethylene-fueled (C₂H₄) Hencken burner (25.4 x 25.4 mm² burner) with N₂ co-flow was studied using a Telops infrared IFTS featuring an Indium Antimonide (InSb), 1.5 to 5.5 µm, focal-plane array imaging the scene through a Michelson interferometer. Flame equivalency ratios of Φ = 0.81, 0.91, and 1.11 were imaged on a 128 x 200 pixel array with a 0.48 mm per pixel spatial resolution and 0.5 cm^-1 spectral resolution. A single-layer radiative transfer model based on the Line-by-Line Radiative Transfer Model (LBLRTM) code and High Resolution Transmission (HITRAN) spectral database for high-temperature work (HITEMP) was used to simultaneously retrieve temperature (T) and concentrations of water (H₂O) and carbon dioxide (CO₂) from individual pixel spectra between 3100-3500 cm^-1 spanning the flame at heights of 5 mm and 10 mm above the burner. CO₂ values were not determined as reliably as H₂O due to its smooth, unstructured spectral features in this window. At 5 mm height near flame center, spectrally-estimated T's were 2150, 2200, & 2125 K for Φ = 0.81, 0.91, & 1.11 respectively, which are within 5% of previously reported experimental findings. Additionally, T & H₂O compared favorably to adiabatic flame temperatures (2175, 2300, 2385 K) and equilibrium concentrations (10.4, 11.4, 12.8%) computed by NASA-Glenn's Chemical Equilibrium with Applications (CEA) program. UNICORN CFD predictions were in excellent agreement with CEA calculations at flame center, and predicted a fall-off in both T and H₂O with distance from flame center more slowly than the spectrally-estimated values. This is likely a shortcoming of the homogeneous assumption imposed by the single-layer model. Pixel-to-pixel variations in T and H₂O were observed.

AFIT Designator

AFIT-ENP-13-M-36

DTIC Accession Number

ADA583715

Recommended Citation

Westman, Andrew J., "Study of Laminar Flame 2-D Scalar Values at Various Fuel to Air Ratios Using an Imaging Fourier-Transform Spectrometer and 2-D CFD Analysis" (2013). Theses and Dissertations. 950.
https://scholar.afit.edu/etd/950