The flamelet model for non-premixed combustion

Abstract

The flamelet approach for non-premixed combustion is based on the description of the turbulent flame as a collection of laminar flame elements embedded in a turbulent flow and interacting with it. The local structure of the flame at each point of the flame front is supposed to be similar to a laminar flamelet, while the interaction with turbulence is reduced to the front evolution. This view is supported by the introduction of the mixture fraction, which allows to decouple the turbulent transport and the flame structure. One key parameter of the flamelet structure is the scalar dissipation rate, which controls the reactant fluxes to the reaction zone and is related to the flow velocity gradients. Probability density functions or flame surface density are then used to describe the turbulent flame and relate the flamelet description to the turbulent flame front. As unsteady effects may become significant, various transient flamelet approaches also exist to take into account the flame history. The flamelet approach may be used either in the RANS or LES context and is still being developed to account for additional complexities such as heat losses and sprays. © Springer Science+Business Media B.V. 2011.