Flamelet Generated Manifold Combustion Model Research Articles

Verification of temperature and toxic species in methane compartment fire using flamelet generated manifold with radiation effect

This paper examined the effect of combustion model on compartment fire simulation. The results of the flamelet generated manifold (FGM) combustion model were compared with conventional combustion models in compartment fire simulation. Methane fuel was selected and the detailed kinetic mechanism was chosen for the FGM model. In addition, the radiation effect was investigated on the FGM combustion model. It was observed that it was necessary to apply the radiation effect in the FGM combustion model for the high heat release rate. For example, the temperature of FGM-base (in the absence of radiation effect) over-predicted near the ceiling of the room at heat release rate of 265 kW. However, if radiation effect was applied, the mean temperature reached 1250 K and the relative error was reduced to less than 10%. The important point is that the computational cost of the FGM was equal to other conventional combustion models in fire simulation. In addition, the conventional combustion models could model only one or two toxic species. However, the FGM was able to model all toxic species involved in the fire.

Numerical Simulations of Heat Loss Effect on Premixed Jet Flame Using Flamelet Generated Manifold Combustion Model

Numerical simulations are performed on a combustor setup which represents the recirculating behaviour of a combustor in the flameless combustion regime. Previous experimental and numerical studies showed that heat loss is prominent for this setup. Here, the amount of heat loss through the combustor walls is quantified and its effect analysed. For this a non-adiabatic Flamelet Generated Manifold (FGM) model is employed. This model uses tabulated chemistry in combination with governing equations for a small set of control variables to accurately describe a turbulent flame. In the current implementation, equations for enthalpy and the mean and variance of the reaction progress variable are solved. Turbulence-chemistry interactions are incorporated through a presumed-PDF approach. In contrast to earlier work, the model is applied in the commercial solver Ansys CFX, coupled to a low-mach, compressible, steady-state Reynolds-Averaged Navier-Stokes (RANS) turbulence model. Results from the simulations show that heat loss consumes over 30% of the combustor’s thermal power. Despite this large heat loss, its effect on the combustion chemistry is small. The inclusion of heat loss in the chemistry tabulation does improve the prediction of the velocity and temperature field in the primary reaction zone. However, the effect of including heat loss is limited in the prediction of species concentrations.

Numerical investigation of heat transfer effects on combustion in a generic gas turbine burner

PurposeThis study aims to methodologically investigate heat transfer effects on reacting flow inside a liquid-fueled, swirl-stabilized burner. Furthermore, particular attention is paid to turbulence modeling and the results of Reynolds-averaged Navier–Stokes and large eddy simulation approaches are compared in terms of velocity field and flame temperature.Design/methodology/approachSimulations consist liquid fuel distribution using Eulerian–Lagrangian approach. Flamelet-Generated Manifold combustion model, which is a mixture fraction-progress variable formulation, is used to obtain reacting flow field. Discrete ordinates method is also added for modeling radiation heat transfer effect inside the burner. As a parametric study, different thermal boundary conditions namely: adiabatic wall, constant temperature and heat transfer coefficient are applied. Because of the fact that the burner is designed for operating with different materials, the effects of burner material on heat transfer and combustion processes are investigated. Additionally, material temperatures have been calculated using 1 D method. Finally, soot particles, which are source of luminous radiation in gas turbine combustors, are calculated using Moss-Brookes model.FindingsThe results show that the flow behavior is obviously different in recirculation region for both turbulence modeling approach, and this difference causes change on flame temperature distribution, particularly in the outer recirculation zone and region close to swirler. In thermal assessment of the burner, it is predicted that material of the burner walls and the applied thermal boundary conditions have significant influence on flame temperature, wall temperature and flow field. The radiation heat transfer also makes a strong impact on combustion inside the burner; however, luminous radiation arising from soot particles is negligible for the current case.Originality/valueThese types of burners are widely used in research of gas turbine combustion, and it can be seen that the heat transfer effects are generally neglected or oversimplified in the literature. This parametric study provides a basic understanding and methodology of the heat transfer effects on combustion to the researchers.

Determining the heating characteristics of non-spherical particles in combusting flows

In order to perform efficient numerical calculations of the heating characteristics of inert, non-spherical particles, an Euler – Lagrangian approach was used for this work. The continuous phase was the combusting flow field in a lab-scale furnace. The Steady Laminar Flamelet (SLF) and the Flamelet Generated Manifold (FGM) combustion model were used for simulations of the continuous phase and the corresponding results were evaluated. It was concluded that the FGM combustion model offers superior performance and moderate computational effort in combustion modelling of air and natural gas. The second phase consisted of discrete coal slag particles which were injected into the furnace. The heating characteristics of spherical and non-spherical particles were evaluated and a model for calculating the temperature of non-spherical particles was validated. The application of the FGM in combination with the Euler-Lagrange approach and specially developed multiphase model adaptions led to very precise results. The maximum deviation between experimentally and numerically determined mean temperatures of non-spherical particles was only 6 K at a temperature level of 680 K.

Investigation of Single-Jet Combustor Near Lean Blowout Conditions Using Flamelet-Generated Manifold Combustion Model and Detailed Chemistry

Numerical simulation results of a single-jet premixed combustion system at atmospheric pressure are compared against comprehensive particle image velocimetry (PIV) flow measurements and Raman scattering temperature measurements for natural gas and hydrogen fuels. The simulations were performed on hexahedral meshes with 1–5 × 106 elements. Reynolds-averaged Navier–Stokes (RANS) calculations were carried out with the k–ε realizable turbulence model. Combustion was modeled using the flamelet-generated manifold model (FGM) and detailed chemistry. Both the flame position and flame liftoff predicted by the FGM were in reasonable agreement with experiments for both fuels and showed little sensitivity to heat transfer or radiation modeling. The detailed chemistry calculation predicts the temperature gradients along the jet centerline accurately and compares very closely with the Raman scattering measurements. The much closer agreement of the jet axial velocity and temperature profiles with experimental values, coupled with the significantly protracted presence of intermediates in the detailed chemistry predictions, indicates that the impact of nonequilibrium intermediates on very lean natural gas flames is significant.