Reynolds-Averaged Navier–Stokes and Large-Eddy Simulation Investigation of Lean Premixed Gas Turbine Combustor

Reynolds-averaged Navier–Stokes (RANS) and large-eddy simulations (LES) of a Siemens scaled combustor are compared against comprehensive experimental data. The steady RANS simulation modeled one quarter of the geometry with 8 M polyhedral cells using the shear stress transport (SST) k-ω model. Unsteady LES were performed on the quarter geometry (90 deg, 8 M cells) as well as the full geometry (360 deg, 32 M cells) using the wall-adapting local eddy-viscosity (WALE) subgrid model and dynamic evaluation of model coefficients. Aside from the turbulence model, all other models are identical for the RANS and LES. Combustion was modeled with the flamelet generated manifold (FGM) model, which represents the thermochemistry by mixture fraction and reaction progress. RANS simulations are performed using Zimont and Peters turbulent flame-speed (TFS) expressions with default model constants, as well as the kinetic rate from the FGM. The flame-speed stalls near the wall with the TFS models, predicting a flame brush that extends to the combustor outlet, which is inconsistent with measurements. The FGM kinetic source model shows improved flame position predictions. The LES predictions of mean and rms axial velocity, mixture fraction, and temperature do not show improvement over the RANS. All three simulations overpredict the turbulent mixing in the inner recirculation zone, causing flatter profiles than measurements. This overmixing is exacerbated in the 90 deg case. The experiments show evidence of heat loss, and the adiabatic simulations presented here might be improved by including wall heat-loss and radiation effects.

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A Comparison of RANS and LES of an Industrial Lean Premixed Burner

Volume 4A: Combustion, Fuels and Emissions ◽

10.1115/gt2014-25352 ◽

2014 ◽

Cited By ~ 2

Author(s):

Graham Goldin ◽

Federico Montanari ◽

Sunil Patil

Keyword(s):

Heat Loss ◽

Radiation Effects ◽

Mixture Fraction ◽

Turbulent Flame ◽

Source Model ◽

Flame Speed ◽

Turbulent Flame Speed ◽

Flamelet Generated Manifold ◽

Rans Simulations ◽

Polyhedral Cells

LES and RANS simulations of a Siemens scaled combustor are compared against comprehensive experimental data. The steady RANS simulation modeled one quarter of the geometry with 8M polyhedral cells using the SST-k-ω model. Unsteady LES simulations were performed on the quarter geometry (90°, 8M cells) as well as the full geometry (360°, 32M cells) using the WALE sub-grid model and dynamic evaluation of model coefficients. Aside from the turbulence model, all other models are identical for the RANS and LES. Combustion was modeled with the Flamelet Generated Manifold (FGM) model, which represents the thermo-chemistry by mixture fraction and reaction progress. RANS simulations are performed using Zimont and Peters turbulent flame speed (TFS) expressions with default model constants, as well as the kinetic rate from the FGM. The flame speed stalls near the wall with the TFS models, predicting a flame brush that extends to the combustor outlet, which is inconsistent with measurements. The FGM kinetic source model shows improved flame position predictions. The LES predictions of mean and rms axial velocity, mixture fraction and temperature do not show improvement over the RANS. All three simulations over-predict the turbulent mixing in the inner recirculation zone, causing flatter profiles than measurements. This over-mixing is exacerbated in the 900 case. The experiments show evidence of heat loss and the adiabatic simulations presented here might be improved by including wall heat-loss and radiation effects.

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Investigation of Flamelet Generated Manifold Reaction Source Term Closure Models Applied to an Industrial Gas Turbine

Volume 4A: Combustion, Fuels, and Emissions ◽

10.1115/gt2019-90219 ◽

2019 ◽

Author(s):

George Mallouppas ◽

Graham Goldin ◽

Yongzhe Zhang ◽

Piyush Thakre ◽

Jim Rogerson

Keyword(s):

Gas Turbine ◽

Source Term ◽

Mixture Fraction ◽

Turbulent Flame ◽

Flame Speed ◽

Turbulent Flame Speed ◽

Progress Variable ◽

Flamelet Generated Manifold ◽

Reactor Types ◽

Industrial Gas Turbine

Abstract Three Flamelet Generated Manifold reaction source term closure options and two different reactor types are examined with Large Eddy Simulation of an industrial gas turbine combustor operating at 3 bar. This work presents the results for the SGT-100 Dry Low Emission (DLE) gas turbine provided by Siemens Industrial Turbomachinery Ltd. The related experimental study was performed at the German Aerospace Centre, DLR, Stuttgart, Germany. The FGM model approximates the thermo-chemistry in a turbulent flame as that in a simple 0D constant pressure ignition reactors and 1D strained opposed-flow premixed reactors, parametrized by mixture fraction, progress variable, enthalpy and pressure. The first objective of this work is to compare the flame shape and position predicted by these two FGM reactor types. The Kinetic Rate (KR) model, studied in this work, uses the chemical rate from the FGM with assumed shapes, which are a Beta function for mixture fraction and delta functions for reaction progress variable and enthalpy. Another model investigated is the Turbulent Flame-Speed Closure (TFC) model with Zimont turbulent flame speed, which propagates premixed flame fronts at specified turbulent flame speeds. The Thickened Flame Model (TFM), which artificially thickens the flame to sufficiently resolve the internal flame structure on the computational grid, is also explored. Therefore, a second objective of this paper is to compare KR, TFC and TFM with the available experimental data.

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Modeling of Inhomogeneously Premixed Combustion With an Extended TFC Model

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.1394964 ◽

2000 ◽

Vol 124 (1) ◽

pp. 58-65 ◽

Cited By ~ 28

Author(s):

W. Polifke ◽

P. Flohr ◽

M. Brandt

Keyword(s):

Laminar Flame ◽

Mixture Fraction ◽

Turbulent Flame ◽

Flame Temperature ◽

Flame Speed ◽

Premixed Combustion ◽

Combustion Stability ◽

Model Parameters ◽

Turbulent Flame Speed ◽

Functional Relationships

In many practical applications, so-called premixed burners do not achieve perfect premixing of fuel and air. Instead, fuel injection pressure is limited, the permissible burner pressure drop is small and mixing lengths are curtailed to reduce the danger of flashback. Furthermore, internal or external piloting is frequently employed to improve combustion stability, while part-load operation often requires burner staging, where neighboring burners operate with unequal fuel/air equivalence ratios. In this report, an extension of the turbulent flame speed closure (TFC) model for highly turbulent premixed combustion is presented, which allows application of the model to the case of inhomogeneously premixed combustion. The extension is quite straightforward, i.e., the dependence of model parameters on mixture fraction is accounted for by providing appropriate lookup tables or functional relationships to the model. The model parameters determined in this way are adiabatic flame temperature, laminar flame speed and critical gradient. The model has been validated against a test case from the open literature and applied to an externally piloted industrial gas turbine burner with good success.

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Modeling CO With Flamelet-Generated Manifolds: Part 2 — Application

Volume 2: Combustion, Fuels and Emissions, Parts A and B ◽

10.1115/gt2012-69546 ◽

2012 ◽

Cited By ~ 1

Author(s):

Graham Goldin ◽

Zhuyin Ren ◽

Hendrik Forkel ◽

Liuyan Lu ◽

Venkat Tangirala ◽

...

Keyword(s):

Reaction Rate ◽

Source Term ◽

Turbulent Flame ◽

Leading Edge ◽

Flame Speed ◽

Reaction Progress ◽

Turbulent Flame Speed ◽

Flamelet Generated Manifold ◽

The Mean ◽

Flame Brush

Conventional Flamelet Generated Manifold (FGM) closure of the mean progress variable reaction rate assumes PDF shapes to account for turbulent fluctuations. The FGM parameters are commonly assumed to be statistically independent, and the marginal PDFs invariably require second moments, which are difficult to model accurately and have limited coefficients that can be adjusted to calibrate the simulation. A new model is presented which locates the flame brush with a turbulent flame speed model, and applies the FGM kinetic rate to model kinetically limited processes, such as CO quenching, behind the flame-front. The model is applied to 3D RANS simulations of an equivalence ratio sweep in the GE Entitlement Rig perfectly premixed combustor experiment. Calculating the mean FGM reaction progress source term with standard assumed shape PDFs leads to a narrow flame brush and equilibrium CO outlet emissions. By limiting the mean FGM reaction progress source term by the turbulent flame speed model, the flame brush is broadened and super-equilibrium CO is predicted at the outlet. Good agreement with measurement is obtained with default model coefficients. Since the majority of the mean reaction progress source term is limited by the turbulent flame speed reaction rate, it is demonstrated that the model is relatively insensitive to assumed shape PDFs for the FGM rate, as well as the parameter used to determine the turbulent flame leading edge.

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Modeling of Inhomogeneously Premixed Combustion With an Extended TFC Model

Volume 2: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations ◽

10.1115/2000-gt-0135 ◽

2000 ◽

Cited By ~ 2

Author(s):

Wolfgang Polifke ◽

Peter Flohr ◽

Martin Brandt

Keyword(s):

Laminar Flame ◽

Mixture Fraction ◽

Turbulent Flame ◽

Flame Temperature ◽

Flame Speed ◽

Premixed Combustion ◽

Combustion Stability ◽

Model Parameters ◽

Turbulent Flame Speed ◽

Functional Relationships

In many practical applications, so-called premixed burners do not achieve perfect premixing of fuel and air. Instead, fuel injection pressure is limited, the permissible burner pressure drop is small and mixing lengths are curtailed to reduce the danger of flashback. Furthermore, internal or external piloting is frequently employed to improve combustion stability, while part-load operation often requires burner staging, where neighboring burners operate with unequal fuel/air equivalence ratios. In this report, an extension of the Turbulent Flame speed Closure (TFC) model for highly turbulent premixed combustion is presented, which allows application of the model to the case of inhomogeneously premixed combustion. The extension is quite straightforward, i.e. the dependence of model parameters on mixture fraction is accounted for by providing appropriate lookup tables or functional relationships to the model. The model parameters determined in this way are adiabatic flame temperature, laminar flame speed and critical gradient. The model has been validated against a test case from the open literature and applied to an externally piloted industrial gas turbine burner with good success.

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Numerical Investigation of Pressure Influence on the Confined Turbulent Boundary Layer Flashback Process

Fluids ◽

10.3390/fluids4030146 ◽

2019 ◽

Vol 4 (3) ◽

pp. 146 ◽

Cited By ~ 2

Author(s):

Aaron Endres ◽

Thomas Sattelmayer

Keyword(s):

Boundary Layer ◽

Gas Turbines ◽

Separation Zone ◽

Turbulent Flame ◽

Pressure Rise ◽

Flame Speed ◽

Zone Size ◽

Detailed Chemical Kinetics ◽

Turbulent Flame Speed ◽

Quenching Distance

Boundary layer flashback from the combustion chamber into the premixing section is a threat associated with the premixed combustion of hydrogen-containing fuels in gas turbines. In this study, the effect of pressure on the confined flashback behaviour of hydrogen-air flames was investigated numerically. This was done by means of large eddy simulations with finite rate chemistry as well as detailed chemical kinetics and diffusion models at pressures between 0 . 5 and 3 . It was found that the flashback propensity increases with increasing pressure. The separation zone size and the turbulent flame speed at flashback conditions decrease with increasing pressure, which decreases flashback propensity. At the same time the quenching distance decreases with increasing pressure, which increases flashback propensity. It is not possible to predict the occurrence of boundary layer flashback based on the turbulent flame speed or the ratio of separation zone size to quenching distance alone. Instead the interaction of all effects has to be accounted for when modelling boundary layer flashback. It was further found that the pressure rise ahead of the flame cannot be approximated by one-dimensional analyses and that the assumptions of the boundary layer theory are not satisfied during confined boundary layer flashback.

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