Large Eddy Simulations of Bluff-Body Stabilized Turbulent Flames and Gas Turbine Combustors

The paper presents applications of the large eddy simulation (LES) methodology on the Sandia/Sydney turbulent bluffbody burner and gas turbine combustors. LES of the bluffbody flame is performed using the filtered density function (FDF) submodel and a comprehensive augmented chemical mechanism for the first time. The FDF submodel is a sophisticated turbulent-combustion submodel that directly computes the joint probability density function (PDF) of scalars and is therefore considered to be more accurate than conventional assumed-PDF type models. The chemical kinetics mechanism involves 19 species and 15 reaction-steps. The mechanism contains both C1 and C2 species and also involves NO formation steps. Owing to the complexity of the mechanism, numerical integration of the kinetics equations is performed using the in situ adaptive tabulation (ISAT) scheme. Mean velocity and species/temperature fields are presented and compared to experimental data. Results show that the computations are in good agreement with data. The paper also presents LES of a gas turbine combustor. LES is performed using an assumed FDF turbulent-combustion model in conjunction with the flamelet-generated manifold method. The advantage of this approach is that the chemical reaction is parameterized by only two variables, mixture fraction and progress variable. Thus calculations are significantly faster than those with the transport FDF model. Circumferentially averaged combustor exit fuel-air ratio profiles are compared to measurement data for two liner port patterns. It is shown that the LES calculations are in reasonable agreement with data and superior to Reynolds averaged Navier- Stokes calculations. These calculations indicate that LES of practical combustion systems are feasible economically and can be used for design analyses more routinely.