Experimental Investigation of Premixed Turbulent Combustion in High Reynolds Number Regimes using PLIF

Abstract

Premixed turbulent flame structures are imaged with simultaneous formaldehyde and OH PLIF. A new piloted burner was designed to achieve high turbulent Reynolds numbers (Ret) up to 68,000 and low Damkohler numbers (Dat). Primary reaction zones are identified by the overlap of the OH and formaldehyde signals and preheat zones of low temperature secondary reactions are identified from the formaldehyde signal. At low Ret of 600, the primary reaction zones are continuous and products do not mix with reactants. This results in thin preheat layers and relatively thin flamelets. As Ret increases, the primary reaction zones become shredded and disconnected. This allows mixing of the hot products with the reactants and broadens the preheat/secondary reaction zones. Additionally, the reaction layers are typically 4-5 times thicker than those in a laminar flamelet. Interestingly, as Ret increases further, the thickness of the reaction layers only increases slowly, but the total area of reaction regions grows rapidly.