Development of large eddy simulation for turbulent combustion flows

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This research aimed a development of large eddy simulation (LES) for turbulent combustion flows for the advanced design of combustors of energy plants or gas turbines. Based on the flamelet assumption which was developed in time-averaged turbulence modeling, LES methods and their subgrid scale (SGS) model are developed for various types of turbulence flames and the combined combustion flows. A dynamic SGS model is introduced into the turbulent flame models. As practical applications, prediction method for NO production in turbulent flames and combustion model of spray fuels are investigated based on the above LES modeling. For the practical LES of combustion flows, turbulence models and their numerical methods are developed based on the finite difference and finite element for the complex geometry. Some new results are reported with proposals of non-equilibrium SGS model for scalar transport, wall boundary layer approximation combined with the time-average turbulence models and numerical treatment of inlet velocity fluctuations in jet flows. Since very few cases were reported on instantaneous structures and unsteady scalar transport phenomena in turbulence combustion flows, advanced visualization methods are developed and applied to the basic burner flows. Dynamics and interaction of small scale eddy structures are also investigated using the database of direct numerical simulation. A computer code based on the above researches is probed on the practical problems, as NO prediction in diffusion flame, lift-up flame of combustion burner flow prediction in diesel engine cylinder, and premixed flame propagation in multi-stage combustor of advanced gas turbine.