Numerical Simulation of Swirl-Stabilized Premixed Flames With a Turbulent Combustion Model Based on a Systematically Reduced Six-Step Reaction Mechanism

2000 ◽  
Vol 123 (4) ◽  
pp. 832-838 ◽  
Author(s):  
D. E. Bohn ◽  
J. Lepers
Keyword(s):  
Reaction Mechanism ◽  
Turbulent Combustion ◽  
Atmospheric Pressure ◽  
Elevated Pressure ◽  
Combustion Model ◽  
Direct Computation ◽  
Nox Formation ◽  
Gas Combustion ◽  
Fuel Gas ◽  
No Formation

This paper presents the application of a detailed combustion model for turbulent premixed combustion to a swirl-stabilized premix burner. Computations are carried out for atmospheric pressure and elevated pressure of 9 atm. Results of computations for atmospheric pressure are compared to experimental data. The combustion model is of the joint-pdf type. The model is based on the characteristics of turbulent combustion under conditions typical for gas turbine burners. It incorporates a systematically reduced six-step reaction mechanism yielding direct computation of radical concentrations via transport equations or steady-state assumptions. The model is able to simulate combustion of fuel gases containing methane, carbon monoxide, hydrogen, carbon dioxide, and water. It is therefore applicable to both methane and low-BTU fuel gas combustion. Based on computed radical concentrations, a post-processor for NOx formation is applied. This post-processor considers thermal formation of nitrogen oxides and NO formation via the nitrous oxide path.

Numerical Simulation of Swirl-Stabilized Premixed Flames With a Turbulent Combustion Model Based on a Systematically Reduced 6-Step Reaction Mechanism

2000 ◽  
Author(s):  
Dieter E. Bohn ◽  
Joachim Lepers
Keyword(s):  
Reaction Mechanism ◽  
Turbulent Combustion ◽  
Atmospheric Pressure ◽  
Elevated Pressure ◽  
Combustion Model ◽  
Direct Computation ◽  
Nox Formation ◽  
Gas Combustion ◽  
Fuel Gas ◽  
No Formation

This paper presents the application of a detailed combustion model for turbulent premixed combustion to a swirl-stabilized premix burner. Computations are carried out for atmospheric pressure and elevated pressure of 9 atm. Results of computations for atmospheric pressure are compared to experimental data. The combustion model is of the joint-pdf type. The model is based on the characteristics of turbulent combustion under conditions typical for gas turbine burners. It incorporates a systematically reduced 6-step reaction mechanism yielding direct computation of radical concentrations via transport equations or steady-state assumptions. The model is able to simulate combustion of fuel gases containing methane, carbon monoxide, hydrogen, carbon dioxide and water. It is therefore applicable to both methane and low-BTU fuel gas combustion. Based on computed radical concentrations, a post-processor for NOx-formation is applied. This post-processor considers thermal formation of nitrogen oxides and NO-formation via the nitrous-oxide path.

Simulation of Swirl Combustion and NO Formation Using Various Second Order Moment Turbulent Combustion Models and DNS Verification

2008 ◽  
Author(s):  
F. Wang ◽  
Y. Huang ◽  
L. X. Zhou ◽  
C. X. Xu ◽  
J. Cao
Keyword(s):  
Turbulent Combustion ◽  
Reaction Rate ◽  
Rate Coefficient ◽  
Second Order ◽  
Concentration Fluctuation ◽  
Order Moment ◽  
Combustion Model ◽  
Reaction Rate Coefficient ◽  
No Formation ◽  
Swirl Combustion

If the instantaneous chemistry reaction rate is taken as ws = Bρ2Y1Y2 exp(−E/RT) = ρ2Y1Y2K, here K is a contraction for the exponential term. Then, ignoring the three order fluctuation correlation term, the average reaction rate could be ws = ρ2(Y1Y2K + Y1′Y2′K + Y1K′Y2′ + Y2K′Y1′). The authors have simulated jet combustion and swirl combustion using this kind of second order moment (SOM) turbulent combustion model. The predictions are close to experimental data in most regions. In order to improve the SOM turbulent combustion model, the effect of various correlation moments in the simulation of turbulent swirl combustion and NO formation is studied by comparing different SOM turbulence-chemistry models, including the unified second-order moment (USM) model, the model accounting for only the time-averaged reaction-rate coefficient, the model accounting for only the concentration fluctuation and the model accounting for both the time-averaged reaction-rate coefficient and the concentration fluctuation. These models are incorporated into the FLUENT code for a methane-air swirling combustion and NO formation under various swirl numbers. The magnitude of various correlations and their effect on the time-averaged reaction rate are analyzed, and the simulation results are compared with the corresponding measurement results. The results showed that the USM model gives the best agreement with the experimental results and among various correlation moments the correlation of reaction-rate coefficient fluctuation with the concentration fluctuation is most important. Additionally, a direct numerical simulation (DNS) of three-dimensional channel turbulent reacting flows with consideration of buoyancy effect using a spectral method was carried out. The statistical results are shown that K′Y′ are larger than Y1′Y2′.

scholarly journals Comparison of Combustion Models for Lifted Hydrogen Flames within RANS Framework

Energies ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 152
Author(s):  
Ali Cemal Benim ◽  
Björn Pfeiffelmann
Keyword(s):  
Reaction Mechanism ◽  
Turbulent Combustion ◽  
Reaction Mechanisms ◽  
Numerical Study ◽  
Combustion Reaction ◽  
Combustion Model ◽  
Prediction Quality ◽  
Combustion Models ◽  
Wide Range ◽  
Lift Off

Within the framework of a Reynolds averaged numerical simulation (RANS) methodology for modeling turbulence, a comparative numerical study of turbulent lifted H2/N2 flames is presented. Three different turbulent combustion models, namely, the eddy dissipation model (EDM), the eddy dissipation concept (EDC), and the composition probability density function (PDF) transport model, are considered in the analysis. A wide range of global and detailed combustion reaction mechanisms are investigated. As turbulence model, the Standard k-ε model is used, which delivered a comparatively good accuracy within an initial validation study, performed for a non-reacting H2/N2 jet. The predictions for the lifted H2/N2 flame are compared with the published measurements of other authors, and the relative performance of the turbulent combustion models and combustion reaction mechanisms are assessed. The flame lift-off height is taken as the measure of prediction quality. The results show that the latter depends remarkably on the reaction mechanism and the turbulent combustion model applied. It is observed that a substantially better prediction quality for the whole range of experimentally observed lift-off heights is provided by the PDF model, when applied in combination with a detailed reaction mechanism dedicated for hydrogen combustion.

Modeling of Turbulent Combustion Process and Lean Blowout of Diffusion and Premixed Flames Using a Combined Approach

2009 ◽  
Author(s):  
Yu. G. Kutsenko ◽  
A. A. Inozemtsev ◽  
L. Y. Gomzikov
Keyword(s):  
Diffusion Flame ◽  
Turbulent Combustion ◽  
Diffusion Flames ◽  
Premixed Flames ◽  
Combustion Process ◽  
Combustion Model ◽  
Main Zone ◽  
Lean Blowout ◽  
No Formation ◽  
No Emissions

Most of the modern combustor’s designs use staged concepts for reducing thermal NO emissions. Usually, a combustion process takes place inside the main zone, which uses very lean premixed fuel/air mixtures. A diffusion pilot zone supports combustion process inside a lean main zone. Thermal NO formation process takes place predominantly inside hot diffusion flame. So, operation modes of pilot and main zones must be arranged to provide low NO emissions of pilot zone and maintain flame stability inside the main zone simultaneously. In this paper, a new turbulent combustion model is presented. This model allows to model diffusion and premixed flames and takes into account various physical processes, which lead to flame destabilization. The model uses an equation for reaction progress variable. Within the considered approach this equation has two source terms. These terms are responsible for different conditions of combustion process: diffusion flames and premixed flames, and distributed reacting zones. This paper studies the problem, concerning modeling of lean blowout process of diffusion flame front. To test the proposed combustion model we have simulated lean blowout process inside combustion zone of a gas turbine combustor. Good predictions of lean blowout limits were obtained.

An Algebraic Sub-Grid Scale Turbulent Combustion Model

2010 ◽  
Author(s):  
F. Wang ◽  
F. Leboeuf ◽  
Y. Huang ◽  
L. X. Zhou ◽  
A. I. Sayma
Keyword(s):  
Turbulent Combustion ◽  
Three Dimensional ◽  
Combustion Model ◽  
Buoyancy Effect ◽  
Two Phase ◽  
Gas Combustion ◽  
Spray Flame ◽  
Gas Flame ◽  
Statistical Results ◽  
Good Agreement

A direct numerical simulation (DNS) of three-dimensional turbulent reacting channel flows taking into account the buoyancy effect was carried out using a spectral method. The statistical results from the DNS database are used to validate an algebraic sub-grid scale combustion model (ASSCM), which was studied in gas combustion previously. Comparison between the exact solution and the results of the correlations in the ASSCM model show good agreement in some cases while the results were acceptable other cases. A methane-air gas flame and a methanol-air two-phase spray flame were also simulated using the ASSCM model. The LES predicted temperature profile in both flames were close to the experimental data demonstrating the accuracy of the model.

Staged Premix EV Combustion in Alstom’s GT24 Gas Turbine Engine

2012 ◽  
Author(s):  
Daniel Guyot ◽  
Thiemo Meeuwissen ◽  
Dieter Rebhan
Keyword(s):  
Gas Turbine ◽  
Distribution System ◽  
Fuel Oil ◽  
Operational Flexibility ◽  
Nox Formation ◽  
Diffusion Type ◽  
Fuel Gas ◽  
Start Up ◽  
Reduce Emissions ◽  
Ev Burner

Reducing gas turbine emissions and increasing their operational flexibility are key targets in today’s gas turbine market. In order to further reduce emissions and increase the operational flexibility of its GT24, Alstom has introduced an internally staged premix system into the GT24’s EV combustor. This system features a rich premix mode for GT start-up and a lean premix mode for GT loading and baseload operation. The fuel gas is injected through two premix stages, one injecting fuel into the burner air slots and one injecting fuel into the centre of the burner cone. Both premix stages are in continuous operation throughout the entire operating range, i.e. from ignition to baseload, thus eliminating the previously used pilot operation during start-up with its diffusion-type flame and high levels of NOx formation. The staged EV combustion concept is today a standard on the current GT26 and GT24. The EV burners of the GT26 are identical to the GT24 and fully retrofittable into existing GT24 engines. Furthermore, engines operating only on fuel gas (i.e. no fuel oil operation) no longer require a nitrogen purge and blocking air system so that this system can be disconnected from the GT. Only minor changes to the existing GT24 EV combustor and fuel distribution system are required. This paper presents validation results for the staged EV burner obtained in a single burner test rig at full engine pressure, and in a GT24 field engine, which had been upgraded with the staged EV burner technology in order to reduce emissions and extend the combustor’s operational behavior.

Study on the Effect of Adiabatic Flame Temperature on NOx Formation Using Ethanol Gasoline Blend in SI Engine

2013 ◽  
Vol 781-784 ◽  
pp. 2471-2475 ◽  
Author(s):  
B. M. Masum ◽  
M.A. Kalam ◽  
H.H. Masjuki ◽  
S. M. Palash
Keyword(s):  
Equivalence Ratio ◽  
Gasoline Engine ◽  
Flame Temperature ◽  
Inlet Temperature ◽  
Si Engine ◽  
Nox Formation ◽  
Adiabatic Flame Temperature ◽  
No Formation ◽  
Blended Fuel ◽  
Active Research

Active research and development on using ethanol fuel in gasoline engine had been done for few decades since ethanol served as a potential of infinite fuel supply. This paper discussed analytically and provides data on the effects of compression ratio, equivalence ratio, inlet temperature, inlet pressure and ethanol blend in cylinder adiabatic flame temperature (AFT) and nitrogen oxide (NO) formation of a gasoline engine. Olikara and Borman routines were used to calculate the equilibrium products of combustion for ethanol gasoline blended fuel. The equilibrium values of each species were used to predict AFT and the NO formation of combustion chamber. The result shows that both adiabatic flame temperature and NO formation are lower for ethanol-gasoline blend than gasoline fuel.

Design Analysis of a Micro Gas Turbine Combustion Chamber Burning Natural Gas

2012 ◽  
Author(s):  
André Perpignan V. de Campos ◽  
Fernando L. Sacomano Filho ◽  
Guenther C. Krieger Filho
Keyword(s):  
Experimental Data ◽  
Natural Gas ◽  
Combustion Chamber ◽  
Gas Turbines ◽  
Low Cost ◽  
Mixture Fraction ◽  
Combustion Model ◽  
Inlet Temperature ◽  
Gas Combustion ◽  
Micro Turbine

Gas turbines are reliable energy conversion systems since they are able to operate with variable fuels and independently from seasonal natural changes. Within that reality, micro gas turbines have been increasing the importance of its usage on the onsite generation. Comparatively, less research has been done, leaving more room for improvements in this class of gas turbines. Focusing on the study of a flexible micro turbine set, this work is part of the development of a low cost electric generation micro turbine, which is capable of burning natural gas, LPG and ethanol. It is composed of an originally automotive turbocompressor, a combustion chamber specifically designed for this application, as well as a single stage axial power turbine. The combustion chamber is a reversed flow type and has a swirl stabilized combustor. This paper is dedicated to the diagnosis of the natural gas combustion in this chamber using computational fluid dynamics techniques compared to measured experimental data of temperature inside the combustion chamber. The study emphasizes the near inner wall temperature, turbine inlet temperature and dilution holes effectiveness. The calculation was conducted with the Reynolds Stress turbulence model coupled with the conventional β-PDF equilibrium along with mixture fraction transport combustion model. Thermal radiation was also considered. Reasonable agreement between experimental data and computational simulations was achieved, providing confidence on the phenomena observed on the simulations, which enabled the design improvement suggestions and analysis included in this work.

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