Development of a diagnostic damköhler number for interpreting laser-induced fluorescence data in turbulent flames

Back-support pilot flames are commonly used for stabilization of turbulent, premixed flames in laboratory experiments. These pilot flames produce an adiabatic or super-adiabatic boundary to provide more favorable conditions for combustion. While the use of pilot flames is very common, it’s unclear how these pilot flames change the structure and behavior of the turbulent flames they stabilized. In our recent study of back-support pilot flame effects on flame structure and dynamics in interacting Bunsen flames, we found that the interpretation of laser-induced fluorescence diagnostics was not straightforward in highly strained back-supported flames. In particular, the extinction behavior of these flames is significantly different than in non-back-supported flames and very high rates of steady strain do not lead to extinction as would be the case without back-support. The goal of this study is to use a combination of experiment and simulation to understand the behavior of highly-strained back-supported flames and the interpretation of laser diagnostics under these conditions. In particular, we propose a “diagnostic Damköhler number” as a metric by which one can determine if a steady laminar flamelet concept is a realistic model for interpreting laser-induced fluorescence measurements.