Numerical Simulation of Combustion Instabilities in a Lean Premixed Combustor With Finite Rate Chemistry

2003 ◽  
Author(s):  
David J. Cook ◽  
Heinz Pitsch ◽  
Norbert Peters
Keyword(s):  
Fuel Injection ◽  
Combustion Model ◽  
Analysis Tool ◽  
Computational Domain ◽  
Combustion Instabilities ◽  
Finite Rate ◽  
Flow Area ◽  
Lean Premixed ◽  
Dissipation Model ◽  
Computational Fluid Dynamics Cfd

Combustion instabilities in lean premixed gas turbine combustors remain a major limitation in decreasing NOx emissions. Computational Fluid Dynamics (CFD) has become an important design and analysis tool that is often used to predict thermoacoustic oscillations caused by these instabilities. Limitations to prediction accuracy are imposed by the choice of chemistry and combustion model. The focus of this study is to compare CFD calculations using Eddy Dissipation and Finite Rate Chemistry models to experimental data reported by Richards and Janus (1997) on the single-injector lean premixed DOE-NETL combustor. The computational domain consists of an annular swirl inlet, fuel injection, a can combustor, a plug for reduced flow area, and an exhaust plenum. The numerical calculations were done using a RANS solver. A 2D axisymmetric-swirl model with RANS turbulence model was employed. The Eddy Dissipation Model has become popular largely because of its robust performance. It is shown that this model does not predict combustion instabilities for the present case. On the other hand, the Finite Rate Chemistry Model is numerically stiff, but is capable of capturing the onset of combustion instabilities.

A Simulation Study of the BERL Combustor

2007 ◽  
Author(s):  
Xuelei Chen ◽  
Michael Lorra ◽  
Devin Yeates ◽  
Christopher Jian
Keyword(s):  
Simulation Study ◽  
Turbulence Models ◽  
Combustion Model ◽  
Finite Rate ◽  
Cfd Models ◽  
Dissipation Model ◽  
Computational Fluid Dynamics Cfd ◽  
Pdf Model ◽  
Combustion Processes ◽  
Future Work

A simulation study of the BERL Combustor 1, 2, using Computational Fluid Dynamics (CFD), is presented. This work is part of John Zink Company’s effort to validate the CFD models most frequently used by the Simulation Technology. Solutions group to provide modelling services for its customers and to support internal R&D. The CFD results are carefully compared with the experimental data from the BERL project. The current study focused mainly on combustion models and turbulence models. To simulate combustion processes, the selection of an applicable combustion model is a key decision a CFD engineer has to make. The PDF model, multiple flamelets model, eddy dissipation model, and finite-rate/eddy-dissipation model with two different global rates were tested. Simulation results show that the finite-rate/eddy-dissipation model provided the closest agreement with the BERL data. The standard k-ε, realizable k-ε, RNG k-ε, and Reynolds Stress turbulence models were evaluated as the closures. The simulation study indicates that all the turbulence models yielded good agreement with measurements in the highly reacting zone. However, the accuracy of these models varied in areas away from the reacting zone. In some cases, the discrepancy between the predictions and measurements was as high as 20% at certain locations. Finally, discussions and future work are provided.

Industrial Trent Combustor — Combustion Noise Characteristics

1999 ◽  
Author(s):  
Thomas Scarinci ◽  
John L. Halpin
Keyword(s):  
Fuel Injection ◽  
Power Level ◽  
Technical Problem ◽  
Combustion Noise ◽  
Ambient Conditions ◽  
Noise Mapping ◽  
Noise Characteristics ◽  
Lean Premixed ◽  
In Series ◽  
Three Stages

Thermoacoustic resonance is a difficult technical problem that is experienced by almost all lean-premixed combustors. The Industrial Trent combustor is a novel dry-low-emissions (DLE) combustor design, which incorporates three stages of lean premixed fuel injection in series. The three stages in series allow independent control of two stages — the third stage receives the balance of fuel to maintain the desired power level — at all power conditions. Thus, primary zone and secondary zone temperatures can be independently controlled. This paper examines how the flexibility offered by a 3-stage lean premixed combustion system permits the implementation of a successful combustion noise avoidance strategy at all power conditions and at all ambient conditions. This is because at a given engine condition (power level and day temperature) a characteristic “noise map” can be generated on the engine, independently of the engine running condition. The variable distribution of heat release along the length of the combustor provides an effective mechanism to control the amplitude of longitudinal resonance modes of the combustor. This approach has allowed the Industrial Trent combustion engineers to thoroughly “map out” all longitudinal combustor acoustic modes and design a fuel schedule that can navigate around regions of combustor thermoacoustic resonance. Noise mapping results are presented in detail, together with the development of noise prediction methods (frequency and amplitude) that have allowed the noise characteristics of the engine to be established over the entire operating envelope of the engine.

Prediction of Pressure Rise in a Gas Turbine Exhaust Duct Under Flameout Scenarios While Operating On Hydrogen and Natural Gas Blends

2021 ◽  
Author(s):  
Orlando Ugarte ◽  
Suresh Menon ◽  
Wayne Rattigan ◽  
Paul Winstanley ◽  
Priyank Saxena ◽  
...  
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Combustion Process ◽  
Pressure Rise ◽  
Combustion Model ◽  
Computational Domain ◽  
Cfd Model ◽  
Exhaust Duct ◽  
Gas Turbine Exhaust ◽  
Turbine Exhaust

Abstract In recent years, there is a growing interest in blending hydrogen with natural gas fuels to produce low carbon electricity. It is important to evaluate the safety of gas turbine packages under these conditions, such as late-light off and flameout scenarios. However, the assessment of the safety risks by performing experiments in full-scale exhaust ducts is a very expensive and, potentially, risky endeavor. Computational simulations using a high fidelity CFD model provide a cost-effective way of assessing the safety risk. In this study, a computational model is implemented to perform three dimensional, compressible and unsteady simulations of reacting flows in a gas turbine exhaust duct. Computational results were validated against data obtained at the simulated conditions in a representative geometry. Due to the enormous size of the geometry, special attention was given to the discretization of the computational domain and the combustion model. Results show that CFD model predicts main features of the pressure rise driven by the combustion process. The peak pressures obtained computationally and experimentally differed in 20%. This difference increased up to 45% by reducing the preheated inflow conditions. The effects of rig geometry and flow conditions on the accuracy of the CFD model are discussed.

Combustion Instabilities in Lean Premixed Systems

2016 ◽  
pp. 231-259 ◽  
Author(s):  
J. O'Connor ◽  
S. Hemchandra ◽  
T. Lieuwen
Keyword(s):  
Combustion Instabilities ◽  
Lean Premixed

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.

Comparison of Temperature Fields and Emissions Predictions Using Both an FGM Combustion Model, With Detailed Chemistry, and a Simple Eddy Dissipation Combustion Model With Simple Global Chemistry

2017 ◽  
Author(s):  
Pierre Q. Gauthier
Keyword(s):  
Mixture Fraction ◽  
Temperature Fields ◽  
Combustion Model ◽  
Detailed Chemistry ◽  
Combustion Modeling ◽  
Flamelet Generated Manifold ◽  
Wide Range ◽  
Turbulence Effects ◽  
Air Chemistry ◽  
Dissipation Model

The detailed modeling of the turbulence-chemistry interactions occurring in industrial flames has always been the leading challenge in combustion Computational Fluid Dynamics (CFD). The wide range of flame types found in Industrial Gas Turbine Combustion systems has exacerbated these difficulties greatly, since the combustion modeling approach must be able to predict the flames behavior from regions of fast chemistry, where turbulence has no significant impact on the reactions, to regions where turbulence effects play a significant role within the flame. One of these combustion models, that is being used more and more in industry today, is the Flamelet Generated Manifold (FGM) model, in which the flame properties are parametrized and tabulated based on mixture fraction and flame progress variables. This paper compares the results obtained using an FGM model, with a GRI-3.0 methane-air chemistry mechanism, against the more traditional Industrial work-horse, Finite-Rate Eddy Dissipation Model (FREDM), with a global 2-step Westbrook and Dryer methane-air mechanism. Both models were used to predict the temperature distributions, as well as emissions (NOx and CO) for a conventional, non-premixed, Industrial RB211 combustion system. The object of this work is to: (i) identify any significant differences in the predictive capabilities of each model and (ii) discuss the strengths and weakness of both approaches.

Small Horizontal Axis Wind Turbine: Analytical Blade Design and Comparison With RANS-Prediction and First Experimental Data

2013 ◽  
Author(s):  
Tom Gerhard ◽  
Michael Sturm ◽  
Thomas H. Carolus
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Wind Turbine ◽  
Horizontal Axis ◽  
Analytical Models ◽  
Power Coefficient ◽  
Analysis Tool ◽  
Computational Domain ◽  
Horizontal Axis Wind Turbine ◽  
Data Set

State-of-the-art wind turbine performance prediction is mainly based on semi-analytical models, incorporating blade element momentum (BEM) analysis and empirical models. Full numerical simulation methods can yield the performance of a wind turbine without empirical assumptions. Inherent difficulties are the large computational domain required to capture all effects of the unbounded ambient flow field and the fact that the boundary layer on the blade may be transitional. A modified turbine design method in terms of the velocity triangles, Euler’s turbine equation and BEM is developed. Lift and drag coefficients are obtained from XFOIL, an open source 2D design and analysis tool for subcritical airfoils. A 3 m diameter horizontal axis wind turbine rotor was designed and manufactured. The flow field is predicted by means of a Reynolds-averaged Navier-Stokes simulation. Two turbulence models were utilized: (i) a standard k-ω-SST model, (ii) a laminar/turbulent transition model. The manufactured turbine is placed on the rooftop of the University of Siegen. Three wind anemometers and wind direction sensors are arranged around the turbine. The torque is derived from electric power and the rotational speed via a calibrated grid-connected generator. The agreement between the analytically and CFD-predicted kinematic quantities up- and downstream of the rotor disc is quite satisfactory. However, the blade section drag to lift ratio and hence the power coefficient vary with the turbulence model chosen. Moreover, the experimentally determined power coefficient is considerably lower as predicted by all methods. However, this conclusion is somewhat preliminary since the existing experimental data set needs to be extended.

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