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

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.

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

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.

Validation of a Partially-Premixed Combustion Model for Gas Turbine Applications

2006 ◽  
Author(s):  
L. Caracciolo ◽  
P. A. Rubini
Keyword(s):  
Numerical Simulation ◽  
Gas Turbine ◽  
Computational Efficiency ◽  
Premixed Combustion ◽  
Experimental Results ◽  
Combustion Model ◽  
Gas Turbine Combustor ◽  
Accurate Representation ◽  
Combustion Models ◽  
Partially Premixed Combustion

The principal requirements of industry, with respect to the numerical simulation of gas turbine combustors, are computational efficiency and algorithm robustness, together with an accurate representation of the complex fundamental processes. This paper examines the performance of the premixed combustion models implemented in the commercial CFD package Fluent™, in order to validate the ability to model combustion in the context of a premixed gas turbine combustor. The predictions of the model are found to compare well with the experimental results available, demonstrating robustness and computational efficiency.

Large-Eddy Simulation of Combustion Oscillation in Premixed Combustor

1999 ◽  
Author(s):  
Tomoya Murota ◽  
Masaya Ohtsuka
Keyword(s):  
Large Eddy Simulation ◽  
Present Method ◽  
Premixed Combustion ◽  
Compressible Turbulence ◽  
Flamelet Model ◽  
Turbulent Premixed Flame ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Combustion Oscillation ◽  
Combustion Flow

To analyze combustion oscillation in the premixed combustor, a large-eddy simulation program for premixed combustion flow was developed. The subgrid scale (SGS) model of eddy viscosity type for compressible turbulence (Speziale et al., 1988) was adopted to treat the SGS fluxes. The fractal flamelet model, which utilizes the fractal properties of the turbulent premixed flame to obtain the reaction rate, was developed. Premixed combustion without oscillation was analyzed to verify the present method. The computational results showed good accordance with experimental data (Rydén et al., 1993). The combustion oscillation of an “established buzz” type in the premixed combustor (Langhorne, 1988) was also analyzed. The present method succeeded in capturing the oscillation accurately. The detailed mechanism was investigated. The appearance of the non-heat release region, which is generated because the supply of the unburnt gas into the combustion zone stagnates, and its disappearance play an important role.

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

2008 ◽  
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.

Large-Eddy Simulation of Reacting Turbulent Flows in Complex Geometries

2005 ◽  
Vol 73 (3) ◽  
pp. 374-381 ◽  
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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