Pure rotational CARS measurements of temperature and O2-concentration in a low swirl turbulent premixed flame
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Summary, in English
Abstract in Undetermined
Temperature and relative O-2-concentrations have been measured using pure rotational coherent anti-Stokes Raman spectroscopy (RCARS) in a low swirl turbulent premixed flame. This lean flame burning methane has previously been investigated using laser diagnostic techniques and numerical modeling of flame characteristics. In the present work, single-shot RCARS measurements were performed and analysed statistically to obtain temperature and O-2-concentration probability density functions. The results were compared with large eddy simulations (LES) showing fairly good agreement. The rotational CARS technique was successfully applied in the whole range of temperatures (300-1700 K) and relative O-2-concentrations (9-21%), and based on the simultaneous measurements of temperature and O-2-concentration an improved understanding of the reaction progress and air entrainment from the surroundings can be achieved. From the evaluated O-2-concentration, the H2O mole fraction could be estimated, which subsequently made an important thermometric correction possible of up to similar to 40 K at 1700 K by inclusion of N-2-H2O line-broadening coefficients in the theoretical spectral calculations. Spatial averaging effects were observed in a fraction of spectra where both hot and cold spectral envelopes were detected, most often with corresponding peaks displaced relative to each other. The large range of CARS signal intensities (about 3 orders of magnitude) when intermittently probing low and high temperature gases was dealt with by using a multi-track function of the CCD camera that increased the dynamic range. Merits and limitations of pure rotational CARS for diagnostics in turbulent flames are discussed and comparison is made with vibrational CARS. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
Temperature and relative O-2-concentrations have been measured using pure rotational coherent anti-Stokes Raman spectroscopy (RCARS) in a low swirl turbulent premixed flame. This lean flame burning methane has previously been investigated using laser diagnostic techniques and numerical modeling of flame characteristics. In the present work, single-shot RCARS measurements were performed and analysed statistically to obtain temperature and O-2-concentration probability density functions. The results were compared with large eddy simulations (LES) showing fairly good agreement. The rotational CARS technique was successfully applied in the whole range of temperatures (300-1700 K) and relative O-2-concentrations (9-21%), and based on the simultaneous measurements of temperature and O-2-concentration an improved understanding of the reaction progress and air entrainment from the surroundings can be achieved. From the evaluated O-2-concentration, the H2O mole fraction could be estimated, which subsequently made an important thermometric correction possible of up to similar to 40 K at 1700 K by inclusion of N-2-H2O line-broadening coefficients in the theoretical spectral calculations. Spatial averaging effects were observed in a fraction of spectra where both hot and cold spectral envelopes were detected, most often with corresponding peaks displaced relative to each other. The large range of CARS signal intensities (about 3 orders of magnitude) when intermittently probing low and high temperature gases was dealt with by using a multi-track function of the CCD camera that increased the dynamic range. Merits and limitations of pure rotational CARS for diagnostics in turbulent flames are discussed and comparison is made with vibrational CARS. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
Publiceringsår
2013
Språk
Engelska
Sidor
3629-3636
Publikation/Tidskrift/Serie
Proceedings of the Combustion Institute
Volym
34
Dokumenttyp
Artikel i tidskrift
Förlag
Elsevier
Ämne
- Fluid Mechanics and Acoustics
Nyckelord
- Thermometry
- Rotational coherent anti-Stokes Raman spectroscopy
- O-2-Concentration measurements
- Turbulent flame
- Large eddy simulations
Status
Published
ISBN/ISSN/Övrigt
- ISSN: 1540-7489