Comparison of Turbulent-Jet and Bluff-Body Stabilized Flames

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Abstract
The structure of lifted turbulent-jet and bluff-body stabilized flames has been studied experimentally using a planar-imaging techniques based on Raman scattering from CH4. The instantaneous image of CH4 reveal flow and mixing structure information that is lost when time-averaged point measurement techniques are used. Fuel-jet flow and mixing in turbulent-jet and bluff-body flames are characterized by large-scale irregular and lime-varying structures that engulf external fluid. Downstream of the bluff-body face, the fuel jet is stagnated and spread in the radial direction by the dynamics of the high-velocity external air flow. This stagnation process governs how fuel and air mix and subsequently combust in these flames and determines the major differences between jet and bluff-body flames. The instantaneous images were averaged to obtain mean and fluctuating quantities and probability distributions of the CH4 concentration. These time-averaged statistics are interpreted in terms of the large- and small-scale turbulence structure of these flows.