Laser-induced fluorescence thermometry and concentration measurements on NOA?X (0-0) transitions in the exhaust gas of high pressure CH4/air flames

Quantification of NO A–X(0, 2) laser-induced fluorescence: investigation of calibration and collisional influences in high-pressure flames

“…For saturation measurements the energy density was varied from 0.5 to 85 MW͞cm 2 with a dielectric attenuator ͑Laser Optik͒. For all other measurements the energy density was fixed to 15.5 MW͞ cm 2 . Fluorescence signals were collected at right angles to the laser beam and focused with an f ϭ 100 mm, f # ϭ 2 achromatic lens onto the entrance slit of a 500-mm imaging spectrometer ͑Chromex 500IS͒, which was equipped with a 300-groove͞mm grating operated in second order.…”

“…The longer excitation wavelength reduces the risk of generating unwanted interfering fluorescence from hydrocarbons in fuel-rich or from O 2 Schumann-Runge emission in fuel-lean regimes. 2,3 This property can be an advantage for applications in technical combustion, particularly at elevated pressures. In any case, for quantitative interpretation of the signals obtained from LIF measurements the spectral properties that govern the excitation efficiency and the fluorescence quantum yield have to be known.…”

Strategies for laser-induced fluorescence detection of nitric oxide in high-pressure flames III Comparison of A–X excitation schemes

“…22,62 Temperature measurements with NO LIF were also performed by Vyrodov et al in rich premixed methane-air flames up to 30 bar. 63 Several authors reported strong attenuation of the 226-nm laser beam in engines, making in-cylinder measurements impossible at crank angles around top dead center. 43,47 In earlier measurements, we reported laser and signal absorption of nearly 45% at 60 bar despite the small size ͑8-mm diameter͒ of our laboratory flame.…”

Laser-induced-fluorescence detection of nitric oxide in high-pressure flames with A–X(0, 2) excitation

“…The NO D-X͑0, 1͒ system can be probed with 193-nm radiation, e.g., from an ArF excimer laser. 2 The A-X͑0, 0͒ band at 225 nm can be excited with either a frequency-doubled dye laser 3 or a H 2 Raman-shifted KrF excimer laser. 4 The NO D-X͑0, 1͒ system at 193 nm is fine for clean atmospheric-pressure combustion processes in which no species that strongly absorb the exciting laser beam are present.…”

“…The NO A-X͑0, 0͒ system at 225 nm has been applied successfully to measurements in highpressure CH 4 air flames 3 and in engines fueled with propane under conditions up to 20 atm. 8 Because of the large absorption cross sections and the high population of the vibrational ground level, relatively small laser-pulse energies ͑ϳ5 mJ͒ enabled measurements of two-dimensional concentration fields.…”