Laser-saturated fluorescence of nitric oxide and chemiluminescence measurements in premixed ethanol flames

In this study, nitric oxide laser-saturated fluorescence (LSF) measurements were acquired from premixed ethanol flames at atmospheric pressure in a burner. NO-LSF experimental profiles for fuel-rich premixed ethanol flames (Φ = 1.34 and Φ = 1.66) were determined through the excitation/detection scheme of the Q2(26.5) rotational line in the A2Σ+ − X2Π (0, 0) vibronic band and γ(0, 1) emission band. A calibration procedure by NO doping into the flame was applied to establish the NO concentration profiles in these flames. Chemiluminescent emission measurements in the (0, 0) vibronic emission bands of the OH* (A2Σ+ − X2Π) and CH* (A2Δ − X2Π) radicals were also obtained with high spatial and spectral resolution for fuel-rich premixed ethanol flames to correlate them with NO concentrations. Experimental chemiluminescence profiles and the ratios of the integrated areas under emission spectra (ACH*/ACH*(max.) and ACH*/AOH*) were determined. The relationships between chemiluminescence and NO concentrations were established along the premixed ethanol flames. There was a strong connection between CH* radical chemiluminescence and NO formation and the prompt-NO was identified as the governing mechanism for NO production. The results suggest the optimum ratio of the chemiluminescence of two radicals (ACH*/AOH*) for NO diagnostic purposes.