Scale-Adaptive and Large Eddy Simulations of a Turbulent Spray Flame in a Scaled Swirl-Stabilized Gas Turbine Combustor Using Strained Flamelets

In this paper, the three-dimensional (3D) reacting turbulent two-phase flow field of a scaled swirl-stabilized gas turbine combustor is numerically investigated using the commercial CFD software ANSYS FLUENT™-v14. The first scope of this study aims to explicitly compare the predictive capabilities of two turbulence models namely Scale-Adaptive Simulation (SAS) and Large Eddy Simulation (LES) for a reasonable compromise between accuracy of results and global computational cost when applied to simulate swirl-stabilized spray combustion. The second scope of the study is to couple chemical reactions to the turbulent flow using a realistic chemistry model and also to model the local chemical non-equilibrium effects caused by turbulent strain. Standard Eulerian and Lagrangian formulations are used to describe both gaseous and liquid phases respectively. The fuel used is liquid jet-A1 which is injected in the form of a polydisperse spray and the droplet evaporation rate is calculated using the infinite conductivity model. One-component (n-decane) and two-component fuels (n-decane + toluene) are used as jet-A1 surrogates. The combustion model is based on the first and second moments of the mixture fraction, and a presumed-probability density function (PDF) is used to model turbulent-chemistry interactions. The instantaneous thermochemical state necessary for the chemistry tabulation is determined by using initially the partial equilibrium assumption (PEQ) and thereafter, the detailed non-equilibrium (NEQ) calculations through the laminar flamelet concept. The combustion chemistry of these surrogates is represented through a reduced chemical kinetic mechanism (CKM) comprising 1 045 reactions among 139 species, derived from the detailed jet-A1 surrogate model, JetSurf 2.0. Numerical results are compared with a set of published data for a steady spray flame. Firstly, it is observed that, by coupling the two turbulence models with a combustion model incorporating a representative chemistry to account for non-equilibrium effects with realistic fuel properties, the models predict reasonably well the main combustion trends, with a superior performance for LES in terms of trade-off between accuracy and computing time. Secondly, because of some assumptions with the combustion model, some discrepancies are found in the prediction of species slowly produced or consumed such as CO and H2. Finally, the study emphasizes the dominant advantage of an adequate resolution of the mixing characteristics especially with the more demanding simulation of a swirl-stabilized spray flame.

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Large-Eddy Simulation With a New Flamelet Model for Partially Premixed Combustion in a Gas-Turbine Combustor

Volume 1: Boilers and Heat Recovery Steam Generator; Combustion Turbines; Energy Water Sustainability; Fuels, Combustion and Material Handling; Heat Exchangers, Condensers, Cooling Systems, and Balance-of-Plant ◽

10.1115/power-icope2017-3141 ◽

2017 ◽

Author(s):

Keisuke Tanaka ◽

Tomonari Sato ◽

Nobuyuki Oshima ◽

Jiun Kim ◽

Yusuke Takahashi ◽

...

Keyword(s):

Gas Turbine ◽

Diffusion Flame ◽

Premixed Combustion ◽

Combustion Model ◽

Gas Turbine Combustor ◽

Flamelet Model ◽

Eddy Simulation ◽

Partially Premixed Combustion ◽

Large Eddy ◽

Partially Premixed

Turbulent combustion flows in the partially premixed combustion field of a dry low-emission gas-turbine combustor were investigated numerically by large-eddy simulation with a 2-scalar flamelet model. Partially premixed combustion was modelled with 2-scalar coupling based on the conservative function of the mixture fraction and the level set function of the premixed flame surface; the governing equations were then used to calculate the gas temperature in the combustion field with flamelet data. A new combustion model was introduced by defining a nondimensional equilibrium temperature to permit the calculation of adiabatic flame temperatures in the combustion field. Furthermore, a conventional G-equation was modified to include spatial gradient terms for the adiabatic flame temperature to facilitate smooth propagation of a burnt-state region in a predominantly diffusion flame. The effect of flame curvature was adjusted by means of an arbitrary parameter in the equation. The simulation results were compared with those from an experiment and a conventional model. Qualitative comparisons of the instantaneous flame properties showed a dramatic improvement in the new combustion model. Moreover, the experimental outlet temperature agreed well with that predicted by the new model. The model can therefore reproduce the propagation of a predominantly diffusion flame in partially premixed combustion.

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Unsteady RANS and scale adaptive simulations of a turbulent spray flame in a swirled-stabilized gas turbine model combustor using tabulated chemistry

International Journal of Numerical Methods for Heat &amp Fluid Flow ◽

10.1108/hff-09-2014-0272 ◽

2015 ◽

Vol 25 (5) ◽

pp. 1064-1088 ◽

Cited By ~ 9

Author(s):

Alain Fossi ◽

Alain DeChamplain ◽

Benjamin Akih-Kumgeh

Keyword(s):

Gas Turbine ◽

Gas Turbines ◽

Fluid Dynamic ◽

Computational Cost ◽

Turbulence Models ◽

Combustion Model ◽

Time Step ◽

Content Type ◽

Spray Flame ◽

Tabulated Chemistry

Purpose – The purpose of this paper is to numerically investigate the three-dimensional (3D) reacting turbulent two-phase flow field of a scaled swirl-stabilized gas turbine combustor using the commercial computational fluid dynamic (CFD) software ANSYS FLUENT. The first scope of the study aims to explicitly compare the predictive capabilities of two turbulence models namely Unsteady Reynolds Averaged Navier-Stokes and Scale Adaptive Simulation for a reasonable trade-off between accuracy of results and global computational cost when applied to simulate swirl-stabilized spray combustion. The second scope of the study is to couple chemical reactions to the turbulent flow using a realistic chemistry model and also to model the local chemical non-equilibrium(NEQ) effects caused by turbulent strain such as flame stretching. Design/methodology/approach – Standard Eulerian and Lagrangian formulations are used to describe both gaseous and liquid phases, respectively. The computing method includes a two-way coupling in which phase properties and spray source terms are interchanging between the two phases within each coupling time step. The fuel used is liquid jet-A1 which is injected in the form of a polydisperse spray and the droplet evaporation rate is calculated using the infinite conductivity model. One-component (n-decane) and two-component fuels (n-decane+toluene) are used as jet-A1 surrogates. The combustion model is based on the mean mixture fraction and its variance, and a presumed-probability density function is used to model turbulent-chemistry interactions. The instantaneous thermochemical state necessary for the chemistry tabulation is determined by using initially the equilibrium (EQ) assumption and thereafter, detailed NEQ calculations through the steady flamelets concept. The combustion chemistry of these surrogates is represented through a reduced chemical kinetic mechanism (CKM) comprising 1,045 reactions among 139 species, derived from the detailed jet-A1 surrogate model, JetSurf 2.0 using a sensitivity based method, Alternate Species Elimination. Findings – Numerical results of the gas velocity, the gas temperature and the species molar fractions are compared with their experimental counterparts obtained from a steady state flame available in the literature. It is observed that, SAS coupled to the tabulated flamelet-based chemistry, predicts reasonably the main flame trends, while URANS even provided with the same combustion model and computing resources, leads to a poor prediction of the global flame trends, emphasizing the asset of a proper resolution when simulating spray flames. Research limitations/implications – The steady flamelet model even coupled with a robust turbulence model does not reproduce accurately the trend of species with slow oxidation kinetics such as CO and H2, because of the restrictiveness of the solutions space of flamelet equations and the assumption of unity Lewis for all species. Practical implications – This work is adding a contribution for spray flame modeling and can be seen as an extension to the significant efforts for the modeling of gaseous flames using robust turbulence models coupled with the tabulated flamelet-based chemistry approach to considerably reduce computing cost. The exclusive use of a commercial CFD code widely used in the industry allows a direct application of this simulation approach to industrial configurations while keeping computing cost reasonable. Originality/value – This study is useful to engineers interested in designing combustors of gas turbines and others combustion systems fed with liquid fuels.

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Investigation of Siemens SGT-800 Industrial Gas Turbine Combustor Using Different Combustion and Turbulence Models

Volume 4B: Combustion, Fuels and Emissions ◽

10.1115/gt2016-57694 ◽

2016 ◽

Cited By ~ 1

Author(s):

Daniel Lörstad ◽

Anders Ljung ◽

Abdallah Abou-Taouk

Keyword(s):

Gas Turbine ◽

Burning Velocity ◽

Computational Cost ◽

Turbulence Models ◽

Combined Cycle ◽

Combustion Model ◽

Gas Turbine Combustor ◽

Annular Combustor ◽

Industrial Gas Turbine ◽

Spurious Results

Siemens SGT-800 gas turbine is the largest industrial gas turbine within Siemens medium gas turbine size range. The power rating is 53MW at 39% electrical efficiency in open cycle (ISO) and, for its power range, world class combined-cycle performance of >56%. The SGT-800 convectively cooled annular combustor with 30 Dry Low Emissions (DLE) burners has proven, for 50–100% load range, NOx emissions below 15/25ppm for gas/liquids fuels and CO emissions below 5ppm for all fuels, as well as extensive gas fuel flexible DLE capability. In this work the focus is on the combustion modelling of one burner sector of the SGT-800 annular combustor, which includes several challenges since various different physical phenomena interacts in the process. One of the most important aspects of the combustion in a gas turbine combustor is the turbulence chemistry interaction, which is dependent on both the turbulence model and the combustion model. Some turbulence-combustion model combinations that have shown reasonable results for academic generic cases and/or industrial applications at low pressure, might fail when applied to complex geometries at industrial gas turbine conditions since the combustion regime may be different. Therefore is here evaluated the performance of Reynolds Averaged Navier-Stokes (RANS) and Scale Adaptive Simulation (SAS) turbulence models combined with different combustion models, which includes the Eddy Dissipation Model (EDM) combined with Finite Rate Chemistry (FRC) using an optimized reduced 4-step scheme and two flamelet based models; Zimont’s Burning Velocity model and Lindstedt & Vaos Fractal model. The results are compared to obtained engine data and field experience, which includes for example flame position in order to evaluate the advantages and drawbacks of each model. All models could predict the flame shape and position in reasonable agreement with available data; however, for the flamelet based methods adjusted calibration constants were required to avoid a flame too far upstream or non-sufficient burn out which is not in agreement with engine data. In addition both the flamelet based models suffer from spurious results when fresh air is mixed into fully reacted gases and BVM also from spurious results inside the fuel system. The combined EDM-FRC with a properly optimized reduced chemical kinetic scheme seems to minimize these issues without the need of any calibration, with only a slight increase in computational cost.

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Large Eddy Simulation of a Gas-Turbine Combustor Using 2-Scalar Flamelet Approach

Volume 1: Symposia, Parts A and B ◽

10.1115/fedsm2007-37225 ◽

2007 ◽

Author(s):

Takuji Nakashima ◽

Nobuyuki Oshima

Keyword(s):

Large Eddy Simulation ◽

Gas Turbine ◽

Turbulent Combustion ◽

Numerical Prediction ◽

Premixed Combustion ◽

Combustion Reaction ◽

Combustion Model ◽

Gas Turbine Combustor ◽

Eddy Simulation ◽

Large Eddy

To investigate the ability of a numerical prediction method in a practical combustor system, we have conducted a numerical simulation of partially premixed turbulent combustion within a gas-turbine combustor geometry. A combination of Large-Eddy simulation and the 2-scalar flamelet approach are used to simulate unsteady turbulent combustion in modeling turbulent and combustion reaction phenomena and their interactions. With the successful simulation of both the premixed and non-premixed combustion states including the effects of turbulence, the predicted distributions of time-averaged temperature and the O2 mole fraction are found to essentially correspond to the experimental data. In an analysis of the predicted results, the weights of resolved and unresolved phenomena in the numerical prediction are estimated in order to discuss the effects of the turbulent combustion model applied to a practical combustion flow. The analysis determines the effect of turbulence on a Grid Scale that accelerates the premixed combustion reaction, while the modeled effect of turbulence caused by combustion acceleration as shown on a Sub-grid Scale is about twice of the effect as that seen on the Grid Scale.

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Towards Improved Prediction of Aero-Engine Combustor Performance Using Large Eddy Simulations

Volume 3: Combustion, Fuels and Emissions, Parts A and B ◽

10.1115/gt2008-50199 ◽

2008 ◽

Cited By ~ 2

Author(s):

S. James ◽

M. S. Anand ◽

B. Sekar

Keyword(s):

Gas Turbine ◽

Radial Profile ◽

Design Tool ◽

Operating Conditions ◽

Outlet Temperature ◽

Gas Turbine Combustor ◽

Systematic Assessment ◽

Eddy Simulation ◽

Large Eddy ◽

Aero Engine

The paper presents an assessment of large eddy simulation (LES) and conventional Reynolds averaged methods (RANS) for predicting aero-engine gas turbine combustor performance. The performance characteristic that is examined in detail is the radial burner outlet temperature (BOT) or fuel-air ratio profile. Several different combustor configurations, with variations in airflows, geometries, hole patterns and operating conditions are analyzed with both LES and RANS methods. It is seen that LES consistently produces a better match to radial profile as compared to RANS. To assess the predictive capability of LES as a design tool, pretest predictions of radial profile for a combustor configuration are also presented. Overall, the work presented indicates that LES is a more accurate tool and can be used with confidence to guide combustor design. This work is the first systematic assessment of LES versus RANS on industry-relevant aero-engine gas turbine combustors.

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Large-Eddy Simulation of Reacting Turbulent Flows in Complex Geometries

Journal of Applied Mechanics ◽

10.1115/1.2179098 ◽

2005 ◽

Vol 73 (3) ◽

pp. 374-381 ◽

Cited By ~ 86

Author(s):

K. Mahesh ◽

G. Constantinescu ◽

S. Apte ◽

G. Iaccarino ◽

F. Ham ◽

...

Keyword(s):

Large Eddy Simulation ◽

Gas Turbine ◽

Turbulent Flows ◽

Reacting Flows ◽

Gas Turbine Combustor ◽

Turbine Engine ◽

Progress Variable ◽

Eddy Simulation ◽

Variable Approach ◽

Large Eddy

Large-eddy simulation (LES) has traditionally been restricted to fairly simple geometries. This paper discusses LES of reacting flows in geometries as complex as commercial gas turbine engine combustors. The incompressible algorithm developed by Mahesh et al. (J. Comput. Phys., 2004, 197, 215–240) is extended to the zero Mach number equations with heat release. Chemical reactions are modeled using the flamelet/progress variable approach of Pierce and Moin (J. Fluid Mech., 2004, 504, 73–97). The simulations are validated against experiment for methane-air combustion in a coaxial geometry, and jet-A surrogate/air combustion in a gas-turbine combustor geometry.

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Scale-Resolving Simulation of a Propane-Fuelled Industrial Gas Turbine Combustor Using Finite-Rate Tabulated Chemistry

Fluids ◽

10.3390/fluids5030126 ◽

2020 ◽

Vol 5 (3) ◽

pp. 126 ◽

Cited By ~ 1

Author(s):

Kai Zhang ◽

Ali Ghobadian ◽

Jamshid M. Nouri

Keyword(s):

Gas Turbine ◽

Chemical Reaction ◽

Turbulent Flame ◽

Lower Amount ◽

Combustion Model ◽

Gas Turbine Combustor ◽

Finite Rate ◽

Chemistry Method ◽

Tabulated Chemistry ◽

Partially Premixed

The scale-resolving simulation of a practical gas turbine combustor is performed using a partially premixed finite-rate chemistry combustion model. The combustion model assumes finite-rate chemistry by limiting the chemical reaction rate with flame speed. A comparison of the numerical results with the experimental temperature and species mole fraction clearly showed the superiority of the shear stress transport, K-omega, scale adaptive turbulence model (SSTKWSAS). The model outperforms large eddy simulation (LES) in the primary region of the combustor, probably for two reasons. First, the lower amount of mesh employed in the simulation for the industrial-size combustor does not fit the LES’s explicit mesh size dependency requirement, while it is sufficient for the SSTKWSAS simulation. Second, coupling the finite-rate chemistry method with the SSTKWSAS model provides a more reasonable rate of chemical reaction than that predicted by the fast chemistry method used in LES simulation. Other than comparing with the LES data available in the literature, the SSTKWSAS-predicted result is also compared comprehensively with that obtained from the model based on the unsteady Reynolds-averaged Navier–Stokes (URANS) simulation approach. The superiority of the SSTKWSAS model in resolving large eddies is highlighted. Overall, the present study emphasizes the effectiveness and efficiency of coupling a partially premixed combustion model with a scale-resolving simulation method in predicting a swirl-stabilized, multi-jets turbulent flame in a practical, complex gas turbine combustor configuration.

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