Premixed turbulent combustion modeling with flamelet generated manifolds including preferential diffusion effects

Abstract

Paper presented at the 7th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Turkey, 19-21 July, 2010.The FGM technique is a new method to reduce chemical kinetics. It has already proven to be accurate for modelling (partially-) premixed flames in DNS, LES and RANS settings. Previous research has focussed on flames with unit Lewis number transport models, thereby neglecting preferential diffusion effects. High accuracy was gained using a single progress variable Ycv1 to describe the flame kinetics. The method is extended in the present contribution for non-unit Lewis numbers by introducing an additional mixing parameter Ycv2 in the manifold, describing the combined fluctuations in enthalpy and element mass fractions due to flame stretch and preferential diffusion. The resulting 2D FGM is used in 2D DNS of a circular flame and compared with detailed chemistry. The agreement is near perfect thereby opening the way to model 3D turbulent CH4-H2-air flames on a slot burner with realistic non-unit Lewis numbers. A significant increase in flame wrinking occurs due to local changes in burning intensity.