UV laser-induced fluorescence of carbon dioxide in high-pressure flames
Laser-induced fluorescence (LIF) of carbon dioxide (CO2) is investigated with excitation wavelengths between 215 and 255 nm. We present spectrally resolved measurements in premixed CH4/O2/Ar and CH4/air flat-flames at pressures between 5 and 40 bar and fuel/air ratios between 0.8 and 1.9. The LIF signal consists of a broad (200-450 nm) continuum with a faint superimposed band structure, and this signal is absent in similar H2/O2/Ar flames. There is strong evidence this signal arises from CO2, as the variation of signal intensity with excitation wavelength, equivalence ratio and adiabatic flame temperature correlates with CO2 absorption cross-sections recently measured in shock-tube experiments. Linear dependence of LIF signal intensity versus pressure and excitation energy is observed in the investigated ranges. Work to quantify the LIF quantum yield is underway.
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