Quantifying the impact of heat loss, stretch and preferential diffusion effects to the anchoring of bluff body stabilized premixed flames

The response of a premixed flame subjected to either flame stretch (and associated Lewis number effects) or heat loss has been well documented in the literature and has enabled a good understanding of canonical configurations such as flat burner-stabilized, counter flow and tubular flames. However, in practical burners, flames are simultaneously subjected to stretch, heat transfer with the flame holder and preferential diffusion effects. For such flames, usually the collective effect of underlying contributions is studied and individual effects are only treated in a qualitative manner. In this paper, our objective is to use flame stretch theory to separate and quantify the underlying contributions from flame stretch, preferential diffusion and heat transfer with the flame holder to the flame speed of bluff body stabilized flames. It is shown that the theory adequately predicts the flame displacement speed in comparison to the results from the numerical simulations. Using the quantification of contributions, an overall stabilization mechanism for H-2 enriched CH4-air mixtures is discussed. The role of competing contributions from preferential diffusion and heat loss is highlighted especially near the flame base region where the flame speed is heavily impacted by all the effects. Insights are also given for low Lewis number flashback prone flames. (C)& nbsp;2021 The Author(s). Published by Elsevier Inc. on behalf of The Combustion Institute.& nbsp;

Automated summary

This paper uses flame stretch theory to analyze the effects of flame stretch, preferential diffusion, and heat transfer with the flame holder on bluff body stabilized flames. The contributions of each effect to flame speed are separated and quantified. The results are compared to numerical simulations and show good agreement. The study also discusses the stabilization mechanism for hydrogen-enriched CH4-air mixtures and provides insights into low Lewis number flashback prone flames.