OBSERVATION OF THE EFFECTS OF FLOW UNSTEADINESS ON THE CHEMICAL STRUCTURE OF PREMIXED FLAMES
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Date
1999
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Ohio State University
Abstract
Planar laser-induced fluorescence (PLIF) imaging of native diatomic and polyatomic radicals has been applied to investigate the chemical response of a laminar premixed flame subjected to a transient interaction with a laminar vortex pair. This flow exhibits both unsteady curvature and strain and thus may be considered a `unit cell' case for the study of turbulence-chemistry interactions. The experiment indicates substantial under and overshoots in CH and OH, respectively, during the flow transient. These results are not predicted by a numerical simulation (using detailed chemistry and transport models) of the flow. Examination of the computational results indicate a critical need for measurements of polyatomic radicals, particularly those playing a central role in the conversion of fuel to CO, as well as measurements of rates of heat release and species $production ^{a}$. PLIF image results for HCO and $CH_{2}O$ are presented and the application of these data to infer local rates of reaction (e.g. for $OH + CH_{2}O \Rightarrow H_{2}O + HCO$) and heat release are discussed. The reliability of the more traditional measures of flame position or heat release rate (e.g. CH or OH PLIF imaging, and $CH^{\ast}$ or $C_{2}^{\ast}$ chemiluminescence imaging) are considered. Progress in the development of new PLIF imaging tools for other species is presented (e.g. for $CH_{3}, CH_{3}O$ and OCHOCH). The continuing need for high-temperature spectroscopic and collisional energy transfer data for polyatomic flame radical species is also discussed.
Description
$^{a}$ H.N. Najm, P.H. Paul, C.J. Mueller and P.S. Wyckoff, Combustion and Flame 113, 312 (1998).
Author Institution: Sandia National Laboratories
Author Institution: Sandia National Laboratories