Comparison of line-peak and line-scanning excitation in two-color laser-induced-fluorescence thermometry of OH

Stanislav Kostka, Sukesh Roy, Patrick J. Lakusta, Terrence R. Meyer, Michael W. Renfro, James R. Gord, Richard Branam

Research output: Contribution to journalArticlepeer-review

48 Scopus citations


Two-line laser-induced-fluorescence (LIF) thermometry is commonly employed to generate instantaneous planar maps of temperature in unsteady flames. The use of line scanning to extract the ratio of integrated intensities is less common because it precludes instantaneous measurements. Recent advances in the energy output of high-speed, ultraviolet, optical parameter oscillators have made possible the rapid scanning of molecular rovibrational transitions and, hence, the potential to extract information on gas-phase temperatures. In the current study, two-line OH LIF thermometry is performed in a wellcalibrated reacting flow for the purpose of comparing the relative accuracy of various line-pair selections from the literature and quantifying the differences between peak-intensity and spectrally integrated line ratios. Investigated are the effects of collisional quenching, laser absorption, and the integration width for partial scanning of closely spaced lines on the measured temperatures. Data from excitation scans are compared with theoretical line shapes, and experimentally derived temperatures are compared with numerical predictions that were previously validated using coherent anti-Stokes-Raman scattering. Ratios of four pairs of transitions in the A2Σ+←X 2Π (1, 0) band of OH are collected in an atmospheric-pressure, near-adiabatic hydrogen-air flame over a wide range of equivalence ratios-from 0.4 to 1.4. It is observed that measured temperatures based on the ratio of Q1(14)Q1(5) transition lines result in the best accuracy and that line scanning improves the measurement accuracy by as much as threefold at lowequivalence- ratio, low-temperature conditions. These results provide a comprehensive analysis of the procedures required to ensure accurate two-line LIF measurements in reacting flows over a wide range of conditions.

Original languageEnglish
Pages (from-to)6332-6343
Number of pages12
JournalApplied Optics
Issue number32
StatePublished - Nov 10 2009

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Engineering (miscellaneous)
  • Electrical and Electronic Engineering


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