Radical concentration and temperature measurements in sooting flames by cavity ring-down spectroscopy and laser-induced fluorescence

• Main Author: Hu, Yuxuan
• Published: University of Strathclyde 2015
• Subjects: 660
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.668881

Sooting laminar flames at atmospheric pressure present a very complex chemical environment with numerous sources of interference for optical measurement techniques. Absolute concentration profiles of ¹CH₂ and HCO have been measured under a range of flame conditions in a sooting laminar premixed C₂H₄-air flat-flame by Cavity-Ring Down Spectroscopy performed at wavelengths in the range 615 to 625 nm. Also, concentration profiles of the OH radical have been detected via the band of A² ∑(v' = 0) ← X² ∏(v'' = 0) system by Laser-Induced Fluorescence and quantitatively calibrated by Cavity-Ring Down Spectroscopy. In situ measurements of these radicals in sooting flames have hitherto been lacking and are essential for validation of chemical kinetic models of aromatic hydrocarbon and soot formation in flames. The experimental results are compared to simulated concentration profiles generated using the Appel-Bockhorn-Frenklach mechanism. Temperature profiles obtained using OH LIF thermometry are used in interpreting the CRDS data and as input for flame simulation. Additionally, weak broadband absorption is observed by CRDS in the region between the reaction zone and the onset of soot formation; this may be attributable to low concentrations of large aromatic species.