Modelling of flamelet surface-to-volume ratio in turbulent premixed combustion

Flamelet Analysis of Turbulent Combustion

Three-dimensional direct numerical simulations are performed of turbulent combustion of initially spherical flame kernels. The chemistry is described by a progress variable which is attached to a flamelet library. The influence of flame stretch and curvature on the local mass burning rate is studied and compared to an analytical model. It is found that there is a good agreement between the simu...

An elementary model for the validation of flamelet approximations in non-premixed turbulent combustion

The fundamental soundness of three flamelet models for non-premixed turbulent combustion is examined on the basis of their performance in an idealized model problem that merges ideas from the laminar asymptotic theory for non-premixed flames and rigorous homogenization theory for the diffusion of a passive scalar. The overall flame configuration is stabilized by a mean gradient in the passive s...

Modeling autoignition in non-premixed turbulent combustion using a stochastic flamelet approach

In this paper, a stochastic flamelet approach is used to model autoignition in an initially non-premixed medium in isotropic and decaying turbulence, using a one-step irreversible reaction. This configuration corresponds to the DNS data from Sreedhara and Lakshmisha [Proc. Combust. Inst. 29 (2002) 2069]. The system can be described by the flamelet equations for the temperature and fuel mass fra...

Validation of unsteady flamelet models for non-premixed turbulent combustion with intermittency

Flamelets play an important role as subgrid models in large eddy simulations of turbulent flames: they are based on a one-dimensional steady asymptotic solution for the flame. The focus of the present study is to validate their use when unsteadiness and multidimensional effects are present, as to be expected for turbulent flows. To shortcut the prohibitively expansive step of solving the comple...

Extended flamelet model for LES of non-premixed combustion