CFD Analysis of a Complete Industrial Lean Premixed Gas Turbine Combustor

2000 ◽  
Author(s):  
P. Birkby ◽  
R. S. Cant ◽  
W. N. Dawes ◽  
A. A. J. Demargne ◽  
P. C. Dhanasekaran ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Combustion Process ◽  
Operating Conditions ◽  
Combustion Model ◽  
Reacting Flow ◽  
Lean Premixed Combustion ◽  
Fuel Injectors ◽  
Lean Premixed ◽  
Industrial Gas Turbines ◽  
Combustion Technology

The introduction of lean premixed combustion technology in industrial gas turbines has led to a number of interesting technical issues. Lean premixed combustors are especially prone to acoustically-coupled combustion oscillations as well as to other problems of flame stability such as flashback. Clearly it is very important to understand the physics that lies behind such behaviour in order to produce robust and comprehensive remedies, and also to underpin the future development of new combustor designs. Simulation of the flow and combustion using Computational Fluid Dynamics (CFD) offers an attractive way forward, provided that the modelling of turbulence and combustion is adequate and that the technique is applicable to real industrial combustor geometries. The paper presents a series of CFD simulations of the Rolls-Royce Trent industrial combustor carried out using the McNEWT unstructured code. The entire combustion chamber geometry is represented including the premixing ducts, the fuel injectors and the discharge nozzle. A modified k-ε model has been used together with an advanced laminar flamelet combustion model that is sensitive to variations in fuel-air mixture stoichiometry. Detailed results have been obtained for the non-reacting flow field, for the mixing of fuel and air and for the combustion process itself at a number of different operating conditions. The study has provided a great deal of useful information on the operation of the combustor and has demonstrated the value of CFD-based combustion analysis in an industrial context.

Low NOx Advanced Vortex Combustor

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Ryan G. Edmonds ◽  
Joseph T. Williams ◽  
Robert C. Steele ◽  
Douglas L. Straub ◽  
Kent H. Casleton ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Operating Conditions ◽  
Attractive Alternative ◽  
Lean Premixed Combustion ◽  
Wide Range ◽  
Lean Premixed ◽  
Industrial Gas Turbines ◽  
Lean Fuel

A lean-premixed advanced vortex combustor (AVC) has been developed and tested. The natural gas fueled AVC was tested at the U.S. Department of Energy’s National Energy Technology Laboratory in Morgantown, WV. All testing was performed at elevated pressures and inlet temperatures and at lean fuel-air ratios representative of industrial gas turbines. The improved AVC design exhibited simultaneous NOx∕CO∕unburned hydrocarbon (UHC) emissions of 4∕4∕0ppmv (all emissions corrected to 15% O2 dry). The design also achieved less than 3ppmvNOx with combustion efficiencies in excess of 99.5%. The design demonstrated marked acoustic dynamic stability over a wide range of operating conditions, which potentially makes this approach significantly more attractive than other lean-premixed combustion approaches. In addition, the measured 1.75% pressure drop is significantly lower than conventional gas turbine combustors, which could translate into an overall gas turbine cycle efficiency improvement. The relatively high velocities and low pressure drop achievable with this technology make the AVC approach an attractive alternative for syngas fuel applications.

scholarly journals Measurement of Air-Fuel Ratio Fluctuations Caused by Combustor Driven Oscillations

1998 ◽  
Author(s):  
Rajiv Mongia ◽  
Robert Dibble ◽  
Jeff Lovett
Keyword(s):  
Power Spectrum ◽  
Mole Fraction ◽  
Gas Turbines ◽  
Operating Conditions ◽  
Premixed Combustion ◽  
Pollutant Emissions ◽  
Combustion Instabilities ◽  
Pressure Oscillations ◽  
Lean Premixed Combustion ◽  
Lean Premixed

Lean premixed combustion has emerged as a method of achieving low pollutant emissions from gas turbines. A common problem of lean premixed combustion is combustion instability. As conditions inside lean premixed combustors approach the lean flammability limit, large pressure variations are encountered. As a consequence, certain desirable gas turbine operating regimes are not approachable. In minimizing these regimes, combustor designers must rely upon trial and error because combustion instabilities are not well understood (and thus difficult to model). When they occur, pressure oscillations in the combustor can induce fluctuations in fuel mole fraction that can augment the pressure oscillations (undesirable) or dampen the pressure oscillations (desirable). In this paper, we demonstrate a method for measuring the fuel mole fraction oscillations which occur in the premixing section during combustion instabilities produced in the combustor that is downstream of the premixer. The fuel mole fraction in the premixer is measured with kHz resolution by the absorption of light from a 3.39 μm He-Ne laser. A sudden expansion combustor is constructed to demonstrate this fuel mole fraction measurement technique. Under several operating conditions, we measure significant fuel mole fraction fluctuations that are caused by pressure oscillations in the combustion chamber. Since the fuel mole fraction is sampled continuously, a power spectrum is easily generated. The fuel mole fraction power spectrum clearly indicates fuel mole fraction fluctuation frequencies are the same as the pressure fluctuation frequencies under some operating conditions.

scholarly journals Variable Geometry Fuel Injector for Low Emissions Gas Turbines

1999 ◽  
Author(s):  
K. Smith ◽  
R. Steele ◽  
J. Rogers
Keyword(s):  
Gas Turbines ◽  
Field Tests ◽  
Flow Distribution ◽  
Operating Conditions ◽  
Variable Geometry ◽  
Fuel Injector ◽  
System Variable ◽  
Lean Premixed Combustion ◽  
Stable Operating ◽  
Lean Premixed

To extend the stable operating range of a lean premixed combustion system, variable geometry can be used to adjust the combustor air flow distribution as gas turbine operating conditions vary. This paper describes the design and preliminary testing of a lean premixed fuel injector that provides the variable geometry function. Test results from both rig and engine evaluations using natural gas are presented. The variable geometry injector has proven successful in the short-term testing conducted to date. Longer term field tests are planned to demonstrate durability.

Nonlinear Heat-Release/Acoustic Model for Thermoacoustic Instability in Lean Premixed Combustors

1999 ◽  
Vol 121 (3) ◽  
pp. 415-421 ◽  
Author(s):  
A. A. Peracchio ◽  
W. M. Proscia
Keyword(s):  
Heat Release ◽  
Limit Cycle ◽  
Gas Turbines ◽  
Pressure Fluctuations ◽  
Parametric Model ◽  
Operating Conditions ◽  
Cycle Frequency ◽  
Thermoacoustic Instability ◽  
Lean Premixed ◽  
Industrial Gas Turbines

Lean premixed combustors, such as those used in industrial gas turbines to achieve low emissions, are often susceptible to the thermoacoustic combustion instabilities, which manifest themselves as pressure and heat release oscillations in the combustor. These oscillations can result in increased noise and decreased durability due to vibration and flame motion. A physically based nonlinear parametric model has been developed that captures this instability. It describes the coupling of combustor acoustics with the rate of heat release. The model represents this coupling by accounting for the effect of acoustic pressure fluctuations on the varying fuel/air ratio being delivered to the flame, causing a fluctuating heat release due to both fuel air ratio variations and flame front oscillations. If the phasing of the fluctuating heat release and pressure are proper, an instability results that grows into a limit cycle. The nonlinear nature of the model predicts the onset of the instability and additionally captures the resulting limit cycle. Tests of a lean premixed nozzle run at engine scale and engine operating conditions in the UTRC single nozzle rig, conducted under DARPA contract, exhibited instabilities. Parameters from the model were adjusted so that analytical results were consistent with relevant experimental data from this test. The parametric model captures the limit cycle behavior over a range of mean fuel air ratios, showing the instability amplitude (pressure and heat release) to increase and limit cycle frequency to decrease as mean fuel air ratio is reduced.

Ultra-Low NOx Advanced Vortex Combustor

2006 ◽  
Author(s):  
Ryan G. Edmonds ◽  
Robert C. Steele ◽  
Joseph T. Williams ◽  
Douglas L. Straub ◽  
Kent H. Casleton ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Operating Conditions ◽  
Test Facility ◽  
Attractive Alternative ◽  
Lean Premixed Combustion ◽  
Pressure Drops ◽  
Wide Range ◽  
Lean Premixed

An ultra lean-premixed Advanced Vortex Combustor (AVC) has been developed and tested. The natural gas fueled AVC was tested at the U.S. Department of Energy’s National Energy Technology Laboratory (USDOE NETL) test facility in Morgantown (WV). All testing was performed at elevated pressures and inlet temperatures and at lean fuel-air ratios representative of industrial gas turbines. The improved AVC design exhibited simultaneous NOx/CO/UHC emissions of 4/4/0 ppmv (all emissions are at 15% O2 dry). The design also achieved less than 3 ppmv NOx with combustion efficiencies in excess of 99.5%. The design demonstrated tremendous acoustic dynamic stability over a wide range of operating conditions which potentially makes this approach significantly more attractive than other lean premixed combustion approaches. In addition, a pressure drop of 1.75% was measured which is significantly lower than conventional gas turbine combustors. Potentially, this lower pressure drop characteristic of the AVC concept translates into overall gas turbine cycle efficiency improvements of up to one full percentage point. The relatively high velocities and low pressure drops achievable with this technology make the AVC approach an attractive alternative for syngas fuel applications.

scholarly journals Numerical Steady and Transient Evaluation of a Confined Swirl Stabilized Burner

2021 ◽  
Vol 6 (4) ◽  
pp. 46
Author(s):  
Federica Farisco ◽  
Luisa Castellanos ◽  
Jakob Woisetschläger ◽  
Wolfgang Sanz
Keyword(s):  
Heat Release ◽  
Gas Turbines ◽  
Numerical Data ◽  
Operating Conditions ◽  
Main Reaction ◽  
Combustion Model ◽  
Ansys Fluent ◽  
Lean Premixed Combustion ◽  
Flamelet Generated Manifold ◽  
Lift Off

Lean premixed combustion technology became state of the art in recent heavy-duty gas turbines and aeroengines. In combustion chambers operating under fuel-lean conditions, unsteady heat release can augment pressure amplitudes, resulting in component engine damages. In order to achieve deeper knowledge concerning combustion instabilities, it is necessary to analyze in detail combustion processes. The current study supports this by conducting a numerical investigation of combustion in a premixed swirl-stabilized methane burner with operating conditions taken from experimental data that were recently published. It is a follow-up of a previous paper from Farisco et al., 2019 where a different combustion configuration was studied. The commercial code ANSYS Fluent has been used with the aim to perform steady and transient calculations via Large Eddy Simulation (LES) of the current confined methane combustor. A validation of the numerical data has been performed against the available experiments. In this study, the numerical temperature profiles have been compared with the measurements. The heat release parameter has been experimentally and numerically estimated in order to point out the position of the main reaction zone. Several turbulence and combustion models have been investigated with the aim to come into accord with the experiments. The outcome showed that the combustion model Flamelet Generated Manifold (FGM) with the k-ω turbulence model was able to correctly simulate flame lift-off.

Experimental Investigation of Thermoacoustic Oscillations in Syngas Premixed Multi-Swirler Model Combustors

2009 ◽  
Author(s):  
Quanbin Song ◽  
Aibin Fang ◽  
Gang Xu ◽  
Yanji Xu ◽  
Weiguang Huang
Keyword(s):  
Gas Turbines ◽  
Equivalence Ratio ◽  
High Efficiency ◽  
Dynamic Pressure ◽  
Ar Model ◽  
Lean Premixed Combustion ◽  
Lean Premixed ◽  
Industrial Gas Turbines ◽  
Operational Issues ◽  
Thermoacoustic Oscillations

This paper presents the experimental results of the thermoacoustic oscillations in several premixed syngas multi-swirler model combustors. Multi-swirler lean premixed combustion technology has been successfully applied to achieve an anticipative stability, lower noise and high efficiency in industrial gas turbines that burn natural gas or distillated oil. However, some critical operational issues, including combustion oscillations, flashback, blowout and autoignition, should be considered and balanced when burning the coal-derived syngas mainly composed of H2 and CO. In this paper several multi-swirler combustors are tested on an atmospheric-pressure downscaled test rig. Each multi-swirler combustor includes several elemental swirling nozzles with the equal Swirl Number and different array of port configurations. The dynamic pressure, dynamic heat release and critical flashback equivalence ratio are tested in these model combustors burning several kinds of simulated syngases with a similar low heat value. Firstly, the critical equivalence ratios of flashback are shown and compared with those in single-swirler combustors. Secondly, the paper presents the analysis of the temporal and spectral features of dynamic pressure oscillations using many data-processing methods. Thirdly, we describe the bifurcation and retardation phenomenon when the combustion transforms between stable and unstable operations. We also discuss how the equivalence ratio, the fuel composition and the combustor inlet velocity play important roles in determining the amplitudes, the frequencies, the bifurcation and retardation of the thermoacoustic oscillations. Finally, we use a wavelet transformation with a higher resolution in time domain than that with a PSD estimation by the AR model. The processes of amplitude “jump” and flashback are analyzed in details. The results in this paper could improve the current understanding of the nonlinear self-excited and combustion driven thermoacoustic oscillations in gas turbines and give us some references to the development of lean premixed syngas turbines for coal-based IGCC and co-generation systems.

Fuel Interchangeability Effects on the Lean Blowout for a Lean Premixed Swirl Stabilized Fuel Nozzle

2018 ◽  
Author(s):  
Siddhartha Gadiraju ◽  
Suhyeon Park ◽  
Prashant Singh ◽  
Jaideep Pandit ◽  
Srinath V. Ekkad ◽  
...  
Keyword(s):  
Natural Gas ◽  
Gas Turbines ◽  
Flame Temperature ◽  
Operating Conditions ◽  
Fuel Blend ◽  
Lean Blowout ◽  
Fuel Blends ◽  
Lean Premixed ◽  
Combustion Technology ◽  
Fuel Nozzle

This work is motivated by an interest in understanding the fuel interchangeability of a fuel nozzle to operate under extreme lean operating conditions. A lean premixed, swirl-stabilized fuel nozzle designed with central pilot hub was used to test various fuel blends for combustion characteristics. Current gas turbine combustion technology primarily focuses on burning natural gas for industrial systems. However, interest in utilizing additional options due to environmental regulations as well as concerns about energy security have motivated interest in using fuel gases that have blends of Methane, Propane, H2, CO, CO2, and N2. For example, fuel blends of 35%/60% to 55%/35% of CH4/CO2 are typically seen in Landfill gases. Syngas fuels are typically composed primarily of H2, CO, and N2. CH4/N2 fuel blend mixtures can be derived from biomass gasification. Stringent emission requirements for gas turbines stipulate operating at extreme lean conditions, which can reduce NOx emissions. However, lean operating conditions pose the problem of potential blowout resulting in loss of performance and downtime. Therefore, it is important to understand the Lean Blowout (LBO) limits and involved mechanisms that lead to a blowout. While a significant amount of research has been performed to understand lean blowout limits and mechanisms for natural gas, research on LBO limits and mechanisms for fuel blends has only been concentrated on fuel blends of CH4 and H2 such as syngas. This paper studies the lean blowout limits with fuel blends CH4-C3H8, CH4-CO2, and CH4-N2 and also their effect on the stability limits as the pilot fuel percentage was varied. Experimental results demonstrate that the addition of propane, nitrogen and carbon dioxide has minimal effect on the adiabatic flame temperature when the flame becomes unstable under lean operating conditions. On the other hand, the addition of diluent gas showed a potential blowout at higher adiabatic temperatures.

Auto-Ignition in a Gas Turbine Burner at Elevated Temperature

2003 ◽  
Author(s):  
Martin Brandt ◽  
Wolfgang Polifke ◽  
Blazenko Ivancic ◽  
Peter Flohr ◽  
Bettina Paikert
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Internal Combustion Engines ◽  
Cfd Simulation ◽  
Combustion Process ◽  
Reaction Rates ◽  
Operating Conditions ◽  
Lookup Table ◽  
Reacting Flow ◽  
Gas Turbine Burner

Many facilities, e.g. reheat gas turbines or internal combustion engines, are operated with hydrocarbon fuels at elevated preheat temperatures such that conditions may be encountered where the flame is not stabilized by flame propagation, but by self-ignition. A model for turbulent reacting flow in this combustion regime has been developed, based on an ignition indicator representing the evolution of a pool of chemical intermediates. Interactions between turbulence and chemistry are taken into account using a new Monte-Carlo joint PDF approach. The joint PDF is not approximated by an analytical function, but by representative ensembles of particles, which are generated with a biased random number generator. Mean reaction rates are computed from the first and second moments — including co-variances — of those variables which describe the thermochemical state of the mixture. It is possible to calculate mean reaction rates in a pre-processing step and store them in a lookup-table table for use in a subsequent CFD simulation, making the approach very efficient. The model has been implemented in a CFD code and validated against an industrial gas turbine burner configuration. It has been found that the model describes the combustion process for a range of operating conditions with good accuracy.

Prediction Model of NOx for Gas Turbine Combustor With Diffusion and Lean Premixed Flames

1995 ◽  
Author(s):  
Fukuo Maeda ◽  
Yasunori Iwai
Keyword(s):  
Gas Turbine ◽  
Combustion Zone ◽  
Diffusion Flames ◽  
Flow Analysis ◽  
Prediction Method ◽  
Computation Time ◽  
Operating Conditions ◽  
Reacting Flow ◽  
Lean Premixed Combustion ◽  
Lean Premixed

In order to predict the NOx concentration etc., it is necessary to carry out 3-D reacting flow analysis in the combustion zone. However, regardless of improved numerical scheme, and physics-based modeling of flow phenomena and combustion reaction, these techniques not yet reached to a level to be applied to practical combustor problem, because of vast computation time and consequently high computation costs, etc. To improve NOx characterization of new Dry Low NOx Combustor (DLNC) and optimum fuel scheduling for DLNC operations, a NOx prediction method to be applicable for practical combustor problems needs to be developed. In this paper has been proposed a simple semi-empirical model for predicting DLNC NOx emissions that formed from lean premixed combustion flames and diffusion flames. This model comprised of experimental coefficients for adjusting or incorporating effects of practical combustion liner configurations and effects of flow conditions in combustion zone, etc. Also, the present model is applied to newly designed and redesigned DLNC for estimating NOx emission levels and its variation with gas turbine operating conditions, which are compared with the experimental data of full pressure combustion with Natural Gas (NG) fuel.

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