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

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.

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

2014 ◽  
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.

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

2012 ◽  
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.

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

2015 ◽  
Vol 137 (12) ◽  
Author(s):  
Sunil Patil ◽  
Federico Montanari
Keyword(s):  
Heat Loss ◽  
Mixture Fraction ◽  
Turbulent Flame ◽  
Flame Speed ◽  
Navier Stokes ◽  
M Cells ◽  
Turbulent Flame Speed ◽  
Flamelet Generated Manifold ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes

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.

Boundary Layer Flashback Prediction for Turbulent Premixed Jet Flames: Comparison of Two Models

2019 ◽  
Author(s):  
Alireza Kalantari ◽  
Nicolas Auwaijan ◽  
Vincent McDonell
Keyword(s):  
Boundary Layer ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Turbulent Flame ◽  
Flame Speed ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Jet Flames ◽  
Turbulent Flame Speed ◽  
Turbulent Premixed

Abstract Lean-premixed combustion is commonly used in gas turbines to achieve low pollutant emissions, in particular nitrogen oxides. But use of hydrogen-rich fuels in premixed systems can potentially lead to flashback. Adding significant amounts of hydrogen to fuel mixtures substantially impacts the operating range of the combustor. Hence, to incorporate high hydrogen content fuels into gas turbine power generation systems, flashback limits need to be determined at relevant conditions. The present work compares two boundary layer flashback prediction methods developed for turbulent premixed jet flames. The Damköhler model was developed at University of California Irvine (UCI) and evaluated against flashback data from literature including actual engines. The second model was developed at Paul Scherrer Institut (PSI) using data obtained at gas turbine premixer conditions and is based on turbulent flame speed. Despite different overall approaches used, both models characterize flashback in terms of similar parameters. The Damköhler model takes into account the effect of thermal coupling and predicts flashback limits within a reasonable range. But the turbulent flame speed model provides a good agreement for a cooled burner, but shows less agreement for uncooled burner conditions. The impact of hydrogen addition (0 to 100% by volume) to methane or carbon monoxide is also investigated at different operating conditions and flashback prediction trends are consistent with the existing data at atmospheric pressure.

scholarly journals Evaluation of Reduced Kinetics in Simulation of Gasified Biomass Gas Combustion

2013 ◽  
Author(s):  
Xiaoxiang Zhang ◽  
Nur Farizan Munjat ◽  
Jeevan Jayasuriya ◽  
Reza Fakhrai ◽  
Torsten Fransson
Keyword(s):  
Gas Turbine ◽  
Chemical Kinetics ◽  
Cfd Simulation ◽  
Laminar Flame ◽  
Turbulent Flame ◽  
Flame Speed ◽  
Turbulent Flame Speed ◽  
Operation Conditions ◽  
Simulation Results ◽  
Gas Turbine Combustion

It is essentially important to use appropriate chemical kinetic models in the simulation process of gas turbine combustion. To integrate the detailed kinetics into complex combustion simulations has proven to be a computationally expensive task with tens to thousands of elementary reaction steps. It has been suggested that an appropriate simplified kinetics which are computationally efficient could be used instead. Therefore reduced kinetics are often used in CFD simulation of gas turbine combustion. At the same time, simplified kinetics for specific fuels and operation conditions need to be carefully selected to fulfill the accuracy requirements. The applicability of several simplified kinetics for premixed Gasified Biomass Gas (GBG) and air combustion are evaluated in this paper. The current work is motivated by the growing demand of gasified biomass gas (GBG) fueled combustion. Even though simplified kinetic schemes developed for hydrocarbon combustions are published by various researchers, there is little research has been found in literature to evaluate the ability of the simplified chemical kinetics for the GBG combustion. The numerical Simulation tool “CANTERA” is used in the current study for the comparison of both detailed and simplified chemical kinetics. A simulated gas mixture of CO/H2/CH4/CO2/N2 is used for the current evaluation, since the fluctuation of GBG components may have an unpredictable influence on the simulation results. The laminar flame speed has an important influence with flame stability, extinction limits and turbulent flame speed, here it is chosen as an indicator for validation. The simulation results are compared with the experimental data from the previous study [1] which is done by our colleagues. Water vapour which has shown a dilution effect in the experimental study are also put into concern for further validation. As the results indicate, the reduced kinetics which are developed for hydrocarbon or hydrogen combustion need to be highly optimized before using them for GBG combustion. Further optimization of the reduced kinetics is done for GBG and moderate results are achieved using the optimized kinetics compared with the detailed combustion kinetics.

Turbulent flame speed for hydrogen-rich fuel gases at gas turbine relevant conditions

2014 ◽  
Vol 39 (35) ◽  
pp. 20242-20254 ◽  
Author(s):  
Yu-Chun Lin ◽  
Peter Jansohn ◽  
Konstantinos Boulouchos
Keyword(s):  
Gas Turbine ◽  
Turbulent Flame ◽  
Flame Speed ◽  
Turbulent Flame Speed

Modeling of Inhomogeneously Premixed Combustion With an Extended TFC Model

2000 ◽  
Vol 124 (1) ◽  
pp. 58-65 ◽  
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.

Turbulent Flame Speed as an Indicator for Flashback Propensity of Hydrogen-Rich Fuel Gases

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Yu-Chun Lin ◽  
Salvatore Daniele ◽  
Peter Jansohn ◽  
Konstantinos Boulouchos
Keyword(s):  
Gas Turbine ◽  
Flame Propagation ◽  
Carbon Capture ◽  
Turbulent Flame ◽  
Flame Speed ◽  
Turbulent Flame Speed ◽  
Velocity Gradients ◽  
Fuel Mixtures ◽  
Operational Range ◽  
Rich Mixtures

The turbulent flame speed (ST) is proposed to be an indicator of the flashback propensity for hydrogen-rich fuel gases at gas turbine relevant conditions. Flashback is an inevitable issue to be concerned about when introducing fuel gases containing high hydrogen content to gas turbine engines, which are conventionally fueled with natural gas. These hydrogen-containing fuel gases are present in the process of the integrated gasification combined cycle (IGCC), with and without precombustion carbon capture, and both syngas (H2 + CO) and hydrogen with various degrees of inert dilution fall in this category. Thus, a greater understanding of the flashback phenomenon for these mixtures is necessary in order to evolve the IGCC concept (either with or without carbon capture) into a promising candidate for clean power generation. Compared to syngas, the hydrogen-rich fuel mixtures exhibit an even narrower operational envelope between the occurrence of lean blow out and flashback. When flashback occurs, the flame propagation is found to occur exclusively in the boundary layer of the pipe supplying the premixed fuel/air mixture to the combustor. This finding is based on the experimental investigation of turbulent lean-premixed nonswirled confined jet flames for three fuel mixtures with H2 > 70 vol. %. Measurements were performed up to 10 bar at a fixed bulk velocity at the combustor inlet (u0 = 40 m/s) and preheat temperature (T0 = 623 K). Flame front characteristics were retrieved via planar laser-induced fluorescence of the hydroxyl radical (OH-PLIF) diagnostics and the turbulent flame speed (ST) was derived, accordingly, from the perspective of a global consumption rate. Concerning the flashback limit, the operational range of the hydrogen-rich mixtures is found to be well represented by the velocity gradients prescribed by the flame (gc) and the flow (gf), respectively. The former (gc) is determined as ST/(Le × δL0), where Le is the Lewis number and δL0 is the calculated thermal thickness of the one-dimensional laminar flame. The latter (gf) is predicted by the Blasius correlation for fully developed turbulent pipe flow and it indicates the capability with which the flow can counteract the opposed flame propagation. Our results show that the equivalence ratios at which the two velocity gradients reach similar levels correspond well to the flashback limits observed at various pressures. The methodology is also found to be capable of predicting the aforementioned difference in the operational range between syngas and hydrogen-rich mixtures.

Effect of Centrifugal Force on the Performance of High-G Ultra Compact Combustor

2015 ◽  
Author(s):  
Alejandro M. Briones ◽  
Dave L. Burrus ◽  
Timothy J. Erdmann ◽  
Dale T. Shouse
Keyword(s):  
Temperature Profile ◽  
Turbulent Flame ◽  
Flame Length ◽  
Swirl Flow ◽  
Flame Speed ◽  
Reacting Flow ◽  
Flow Conditions ◽  
Radial Temperature ◽  
Turbulent Flame Speed ◽  
Progress Variable

A numerical investigation of reacting flows in an advanced high-g cavity (HGC), Ultra-Compact Combustor (UCC) concept is conducted. The high-g cavity UCC (UCC-HGC) design uses high swirl in a circumferential cavity (CC) wrapped around a main stream annular flow. The high swirl is generated through angled CC driver jets. This centrifugal force is varied by changing the CC-to-core air mass flow ratio (ṁcc/ṁcore) and jet inclination angle (αjet) relative to the cavity ring surface, while maintaining the global equivalence ratio (ϕGlobal) constant. Steady, rotational periodic, 3D simulations are performed following a multiphase, Reynolds-averaged Navier-Stokes (RANS), and non-premixed flamelet/progress variable (FPV) approach using a customized FLUENT. Results indicate that under non-reacting flow conditions the driver jets impose a very strong bulk swirl flow within the CC and the mainstream flow does not entrain into the CC. Thus, the maximum g-load is primarily sensitive to ṁcc/ṁcore and secondarily to αjet. However, the g-loads become increasingly more sensitive to the latter at greater ṁcc/ṁcore. Now, under reacting flow conditions, the flame interacts with the flow and the bulk swirl flow is diminished at low ṁcc/ṁcore, while boosted at high ṁcc/ṁcore. The former happens because the flame deflects the incoming driver jet flow, enhancing radial and axial velocity components (through thermal expansion), while diminishing the tangential flow velocity. This, in turn, weakens the g-loads within the CC to below its design g-load operation. On the other hand, at high ṁcc/ṁcore and small αjet the flame is perpendicular to the bulk swirl flow, accelerating the flow tangential velocity and enhancing g-loads above its design operation. Qualitatively, the more and hotter the flame that can be sustained within the CC the shorter the flame length. The converse is also true. Flame length does not appear to be strongly influenced by ṁcc/ṁcore and αjet. Even though g-loads appear to enhance reaction progress variable source (SC) and, consequently, turbulent flame speed, through turbulence this does not necessarily mean that the turbulent flame speed under g-loads is various factors greater than its corresponding turbulent flame speed under 0g’s. As the ṁcc/ṁcore increases the center-peaked radial temperature profile at intermediate αjet starts to deteriorate, whereas the radial temperature profile at low αjet improves. For high αjet, increasing ṁcc/ṁcore has no substantial effect on the exit radial temperature profiles.

Modeling of Inhomogeneously Premixed Combustion With an Extended TFC Model

2000 ◽  
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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