DOI: 10.1615/ICHMT.2012.ProcSevIntSympTurbHeatTransfPal
ISBN Print: 978-1-56700-302-4
ISSN: 2377-2816
Modeling differential diffusion in Large Eddy Simulation of a bluff body stabilized premixed weakly-turbulent flame
ABSTRACT
Large eddy simulation of the Cambridge swirl burner experiment with a filtered laminar flame (FLF) PDF model is reported. This experiment had shown an accumulation of carbon species in the central re-circulation zone, which was attributed to the preferential diffusion of hydrogen atoms ahead of carbon containing species. Differential diffusion occurs well below typical LES mesh resolution and the challenge is to account for it from resolved scale information. In this work, the differential diffusion induced enhancement of mixture fraction is captured by transporting it with a source term, derived from its budget equation in a 1D laminar premixed flame retaining complex chemistry and Bilger's definition. This strategy worked well in capturing the mean mixture fraction profiles and its fluctuations. A differential diffusion number based on the difference in residence time across the flame and the source term is proposed to estimate qualitatively the presence of this effect in burners.