A tabulated closure for turbulent non-premixed combustion based on the linear eddy model

• Published in: Proceedings of the Combustion Institute 2009, Vol.32 (1), p.1571-1578
• Main Authors: Sankaran, Vaidyanathan, Drozda, Tomasz G., Oefelein, Joseph C.
• Format: Article
• Language: English
• Subjects: Large eddy simulation; Linear eddy model; Turbulent combustion modeling
• ISSN: 1540-7489; 1873-2704
• DOI: 10.1016/j.proci.2008.06.168

A tabulated closure based on conditional statistics from fully-resolved one-dimensional scalar profiles has been formulated for application using the large eddy simulation technique. These scalar profiles are obtained from both experiments (i.e., line imaging of Raman/Rayleigh/CO-LIF) and from the simulations of linear eddy model. Such profiles provide a local description of species and temperature evolution due to the full range of turbulent scales in the predominant direction of scalar transport. Instantaneous realizations of these scalar profiles are processed as a function of pre-determined filter widths in space to obtain the conditional statistics of filtered scalars. Key statistical quantities needed for LES, are then parameterized as a function of a unique filtered state vector. Here, we use the filtered mixture fraction Z∼, filtered scalar dissipation rate χ∼, and the subgrid Reynolds number ReΔ as the filtered state vector. Conditional PDF’s of temperature P(T|Z∼,χ∼,ReΔ), species mass fractions P(Yi|Z∼,χ∼,ReΔ), and relevant thermodynamic and transport properties are tabulated as a function of Z∼, χ∼, and ReΔ. A thermo-chemical state library is then constructed in a manner directly analogous to the conventional flamelet-library approach. The potentially novel feature of this approach is that the relation between filtered and instantaneous quantities is known directly. This eliminates the need for a posteriori models that link these quantities. An a priori analysis of the proposed model was carried out for non-premixed combustion using measurements obtained from CH4/H2/N2 jet flames at a Reynolds numbers of 15,200. This flame exhibits an interesting range of Damköhler and Schmidt numbers through local extinction, reignition, and differential diffusion. Results show good quantitative agreement with measurements.