The filtered mass density function (FMDF) model (Jaberi et al. 1999 [1]) is employed for large eddy simulations (LES) of “high speed” partially-premixed methane jet flames with the “flamelet” and “finite-rate” kinetics models. The FMDF is the joint probability density function (PDF) of the scalars and is determined via the solution of a set of stochastic differential equations. The LES/FMDF is implemented using a highly scalable, parallel hybrid Eulerian–Lagrangian numerical scheme. The LES/FMDF results are shown to compare well with the experimental data for all flow conditions when “appropriate” reaction and mixing models are employed.

VL - 53 IS - 11-12 ER - TY - CONF T1 - Large-Eddy Simulations of Turbulent Methane Jet Flames with Filtered Mass Density Function T2 - National Combustion Meeting Y1 - 2009 A1 - Yaldizli, M. A1 - Mehravaran, K. A1 - Jaberi, F.A. AB -The filtered mass density function (FMDF) model (Jaberi et al. 1999 [1]) is employed for large eddy simulations (LES) of “high speed” partially-premixed methane jet flames with the “flamelet” and “finite-rate” kinetics models. The FMDF is the joint probability density function (PDF) of the scalars and is determined via the solution of a set of stochastic differential equations. The LES/FMDF is implemented using a highly scalable, parallel hybrid Eulerian–Lagrangian numerical scheme. The LES/FMDF results are shown to compare well with the experimental data for all flow conditions when “appropriate” reaction and mixing models are employed.

JF - National Combustion Meeting PB - The Combustion Institute CY - Ann Arbor, Michigan ER - TY - CONF T1 - Filtered Mass Density Function for Numerical Simulations of Spray Combustion T2 - 46th AIAA Aerospace Sciences Meeting and Exhibit Y1 - 2008 A1 - Li, Z. A1 - Jaberi, F.A. A1 - Yaldizli, M. AB -This paper briefly describes our recent efforts on the modeling and numerical simulations of two-phase turbulent reacting flows in realistic combustion systems with a new large-eddy simulation (LES) model. The model is constructed based on the two-phase extension of scalar filtered mass density function (FMDF) and a Lagrangian-Eulerian- Lagrangian mathematical/numerical methodology. In this methodology, the “resolved” fluid velocity field is obtained by solving the filtered form of the compressible Navier-Stokes equations with a high-order finite difference scheme. The liquid (droplet) phase and scalar (temperature and species mass fractions) fields are both obtained by stochastic Lagrangian models. There are two-way interactions between the phases and all the Eulerian and Lagrangian fields. The LES/FMDF is used for systematic analysis of turbulent combustion in the spray-controlled dump combustor and double-swirl spray burner for various flow and spray parameters. The effects of fuel type, spray angle, mass loading ratio, droplet size distribution, fuel/air composition, wall, and inflow/outflow conditions on the combustion are investigated. It has been found that the main features of the turbulence and combustion are modified by changing the inflow/outflow conditions. The LES/FMDF results also confirm the significance of the spray parameters.

JF - 46th AIAA Aerospace Sciences Meeting and Exhibit PB - AIAA CY - Reno, Nevada ER - TY - JOUR T1 - The Structure of Partially-Premixed Methane Flames in High Intensity Turbulent Flows JF - Combustion and Flame Y1 - 2008 A1 - Yaldizli, M. A1 - Mohammad, H. A1 - Mehravaran, K. A1 - Jaberi, F.A. KW - DNS; Methane combustion KW - turbulent reacting flows; partially premixed flames; reduced chemistry models AB -Direct numerical simulations (DNS) are conducted to study the structure of partially premixed and non-premixed methane flames in high-intensity two-dimensional isotropic turbulent flows. The results obtained via “flame normal analysis” show local extinction and reignition for both non-premixed and partially premixed flames. Dynamical analysis of the flame with a Lagrangian method indicates that the time integrated strain rate characterizes the finite-rate chemistry effects and the flame extinction better than the strain rate. It is observed that the flame behavior is affected by the “pressure-dilatation” and “viscous-dissipation” in addition to strain rate. Consistent with previous studies, high vorticity values are detected close to the reaction zone, where the vorticity generation by the “baroclinic torque” was found to be significant. The influences of (initial) Reynolds and Damköhler numbers, and various air–fuel premixing levels on flame and turbulence variables are also studied. It is observed that the flame extinction occurs similarly in flames with different fuel–air premixing. Our simulations also indicate that the CO emission increases as the partial premixing of the fuel with air increases. Higher values of the temperature, the OH mass fraction and the CO mass fraction are observed within the flame zone at higher Reynolds numbers.

VL - 154 IS - 4 ER - TY - CONF T1 - Filtered Mass Density Function for Numerical Simulations of Spray Combustion T2 - 46th AIAA Aerospace Sciences Meeting and Exhibit Y1 - 2007 A1 - Yaldizli, M. A1 - Li, Z. A1 - Jaberi, F.A. AB -This paper briefly describes our recent efforts on the modeling and numerical simulations of two-phase turbulent reacting flows in realistic combustion systems with a new large-eddy simulation (LES) model. The model is constructed based on the two-phase extension of scalar filtered mass density function (FMDF) and a Lagrangian-Eulerian- Lagrangian mathematical/numerical methodology. In this methodology, the “resolved” fluid velocity field is obtained by solving the filtered form of the compressible Navier-Stokes equations with a high-order finite difference scheme. The liquid (droplet) phase and scalar (temperature and species mass fractions) fields are both obtained by stochastic Lagrangian models. There are two-way interactions between the phases and all the Eulerian and Lagrangian fields. The LES/FMDF is used for systematic analysis of turbulent combustion in the spray-controlled dump combustor and double-swirl spray burner for various flow and spray parameters. The effects of fuel type, spray angle, mass loading ratio, droplet size distribution, fuel/air composition, wall, and inflow/outflow conditions on the combustion are investigated. It has been found that the main features of the turbulence and combustion are modified by changing the inflow/outflow conditions. The LES/FMDF results also confirm the significance of the spray parameters.

JF - 46th AIAA Aerospace Sciences Meeting and Exhibit PB - AIAA CY - Reno, Nevada ER - TY - CONF T1 - A New Model for Large Eddy Simulations of Multi-Phase Turbulent Combustion T2 - Proceedings of the 43rd AIAA/ASME/SAI/ASEE Joint Propulsion Conference Y1 - 2007 A1 - Yaldizli, M. A1 - Li, Z. A1 - J.A. Jaberi AB -Numerical simulations of a spray-controlled lean premixed dump combustor are con- ducted via a two-phase large eddy simulation (LES) methodology. In this methodology, the velocity field is obtained by a high-order finite difference method. The subgrid gas- liquid combustion closure is based on the two-phase filtered mass density function (FMDF) method and the spray is modeled with a Lagrangian scheme. The effects of spray, fuel/air composition, and inflow/outflow conditions on the combustion are investigated. It has been found that the main features of the turbulence and combustion inside the dump combustor are very differently modified by the spray for different spray parameters. The LES/FMDF results also indicate the significance of the inflow and outflow conditions.

JF - Proceedings of the 43rd AIAA/ASME/SAI/ASEE Joint Propulsion Conference PB - AIAA/ASME/SAI/ASEE CY - Cincinnati, Ohio ER - TY - Generic T1 - Numerical Simulations of Two-Phase Turbulent Combustion in Spray Burners T2 - ASME Conference Proceedings, Computers and Information in Engineering Conference Y1 - 2007 A1 - Li, Z. A1 - Yaldizli, M. A1 - Jaberi, F.A. AB -The complex interactions among turbulence, combustion and spray in liquid-fuel burners are modeled and simulated via a new two-phase Lagrangian-Eulerian-Lagrangian large eddy simulation (LES) methodology. In this methodology, the spray is modeled with a Lagrangian mathematical/computational method which allows two-way mass, momentum and energy coupling between phases. The subgrid gas-liquid combustion is based on the two-phase filtered mass density function (FMDF) that has several advantages over “conventional” two-phase combustion models. The LES/FMDF is employed in conjunction with non-equilibrium reaction and droplet models. Simulations of turbulent combustion in a spray-controlled double-swirl burner are conducted via LES/FMDF. The generated results are used for better understanding of spray combustion in realistic turbulent flow configurations. The effects of spray angle, mass loading ratio, fuel type, droplet size distribution, wall and inflow/outflow conditions on the flow and combustion are investigated. The LES/FMDF predictions are shown to be consistent with the experimental results.

JF - ASME Conference Proceedings, Computers and Information in Engineering Conference PB - ASME CY - Las Vegas, Nevada SN - 0-7918-4803-5 ER -