The effect of chemistry on Na(3P) saturation curves in fuel-rich and fuel-lean H2O2Ar flames

✍ Scribed by C.A. van den Wijngaart; H.A. Dijkerman; Tj. Hollander; C.Th.J. Alkemade

• Publisher: Elsevier Science
• Year: 1985
• Tongue: English
• Weight: 957 KB
• Volume: 59
• Category: Article
• ISSN: 0010-2180
• DOI: 10.1016/0010-2180(85)90020-3

✦ Synopsis

We observed optical saturation curves of the Na(SP) level in cool (T -1700K) premixed laminar H2-O2-Ar flames at 1 atm and in a wide range of fuel/oxidant ratios below as well as above stoichiometry. A pulsed dye laser (pulse duration of 1.2 /~s) was tuned at the upper doublet component. For this relatively long pulse duration, laser-enhanced molecular formation contributes significantly to the atomic Na depletion. This results in a distortion of the saturation curve and in a downward shift of the saturation parameter. Our theoretical model takes into account the formation of NaOH, Nail, and NaO2. In all our flames laser-enhanced NaOH formation is dominant. From the downstream profile of the saturated fluorescence intensity in the fuel-rich flame, we determined the ratio of the rate constants ofNa + H20, H2 --" NaOH, Nail + H for the Na(SP) and Na(SS): 310 + 60 and (4.5 :t: 0.9) x 104, respectively. Using known cross sections for the quenching of Na(SP) by H20, we derived upper limits for the rate constants of Na + H~O ~ NaOH + H from the 3S and 3P states: 1.2 × 10-~3 cm 3 s-i and 3.7 x 10-N cm-3 s-1, respectively. Our results in the fuel-lean flames support the existence of NaO2-enhanced formation of NaOH at low laser intensity. However, we showed that at high laser intensity laser-enhanced NaOH formation becomes dominant.