Numerical Analysis of NOx Formation in a Diffusion Flame Combustor Based on a Flamelet Model

2001 ◽  
Author(s):  
Dmitry V. Volkov ◽  
Alexandr A. Belokon ◽  
Dmitry A. Lyubimov ◽  
Vladimir M. Zakharov ◽  
George Opdyke
Keyword(s):  
Diffusion Flame ◽  
Turbulent Mixing ◽  
Flow Distribution ◽  
Nox Emission ◽  
Scalar Dissipation ◽  
3D Flow ◽  
Nox Formation ◽  
Flamelet Model ◽  
Primary Zone ◽  
Consumption Rates

Laminar flamelet models have demonstrated good quality predictions of NOx emission from diffusion flame type combustors. In this paper, the NOx formation process is analyzed by using a flamelet model and 3D flow calculations to take a virtual look inside a combustor. The main phenomena affecting NOx emission are turbulent mixing and the turbulence-chemistry interaction. Local scalar dissipation is the main parameter responsible for the turbulence-chemistry interaction within the flamelet model. At the same time, scalar dissipation is also related to the mixing process. On one hand, higher values of scalar dissipation correspond to higher fuel consumption rates, which decrease the volume of the high temperature zones. On the other hand, higher values of scalar dissipation lead to higher NOx formation rates. Unfortunately, scalar dissipation is not commonly used by combustion engineers because of the difficulty of the clear physical interpretation of this variable and its relationship with the usual parameters. In this paper, the influence of several design features, such as primary zone equivalence ratio and air flow distribution along the liner, is studied relative to scalar dissipation distributions in the combustion zones and to NOx formation. A real industrial diffusion flame combustor is used as an example, and the results can provide a better understanding of real combustor processes. The NOx prediction results are in reasonable agreement with test data.

Flamelet Model of NOx in a Diffusion Flame Combustor

2000 ◽  
Author(s):  
Dmitry V. Volkov ◽  
Alexandr A. Belokon ◽  
Dmitry A. Lyubimov ◽  
Vladimir M. Zakharov ◽  
George Opdyke
Keyword(s):  
Diffusion Flame ◽  
Reverse Flow ◽  
Mixture Fraction ◽  
Formation Rate ◽  
Navier Stokes ◽  
Scalar Dissipation ◽  
Nox Formation ◽  
Flamelet Model ◽  
Good Potential ◽  
Detailed Kinetics

This paper describes a model used for the prediction of the formation of nitrogen oxides in modifications of an industrial diffusion flame, natural gas fueled can combustor. The flow field inside the modified combustors is calculated using a Navier-Stokes solver. A fast chemistry assumption is used for modeling the heat release. Calculated turbulence parameters are then used for the calculation of the NOx formation rate in the post-processing mode with the aid of a flamelet model. The flamelet model permits the use of detailed kinetics with only minimal computational expense. The dependence of the NOx formation rate on the mixture fraction and scalar dissipation is calculated separately for each given condition. The validation of the model predictions is based on field test data taken earlier on several low NOx modifications recently applied to an industrial, reverse flow can type combustor. The reduced level of NOx emissions was achieved in these modifications by changes in the air distribution within the combustor liner. A comparison of the predicted and measured NOx emission levels shows good potential of the flamelet model.

Flamelet Model of NOx in a Diffusion Flame Combustor

2000 ◽  
Vol 123 (4) ◽  
pp. 774-778 ◽  
Author(s):  
D. V. Volkov ◽  
A. A. Belokin ◽  
D. A. Lyubimov ◽  
V. M. Zakharov ◽  
G. Opdyke,
Keyword(s):  
Diffusion Flame ◽  
Reverse Flow ◽  
Mixture Fraction ◽  
Formation Rate ◽  
Navier Stokes ◽  
Scalar Dissipation ◽  
Nox Formation ◽  
Flamelet Model ◽  
Good Potential ◽  
Detailed Kinetics

This paper describes a model used for the prediction of the formation of nitrogen oxides in modifications of an industrial diffusion flame, natural gas fueled can combustor. The flowfield inside the modified combustors is calculated using a Navier-Stokes solver. A fast chemistry assumption is used for modeling the heat release. Calculated turbulence parameters are then used for the calculation of the NOx formation rate in the post-processing mode with the aid of a flamelet model. The flamelet model permits the use of detailed kinetics with only minimal computational expense. The dependence of the NOx formation rate on the mixture fraction and scalar dissipation is calculated separately for each given condition. The validation of the model predictions is based on field test data taken earlier on several low NOx modifications recently applied to an industrial, reverse flow can type combustor. The reduced level of NOx emissions was achieved in these modifications by changes in the air distribution within the combustor liner. A comparison of the predicted and measured NOx emission levels shows good potential of the flamelet model.

Predictions of NOx Formation Under Combined Droplet and Partially Premixed Reaction of Diffusion Flame Combustors

1999 ◽  
Vol 124 (1) ◽  
pp. 31-38 ◽  
Author(s):  
N. K. Rizk ◽  
J. S. Chin ◽  
A. W. Marshall ◽  
M. K. Razdan
Keyword(s):  
Diffusion Flame ◽  
Liquid Droplet ◽  
Mixture Distribution ◽  
Fuel Vapor ◽  
Nox Emissions ◽  
Gas Temperature ◽  
Nox Formation ◽  
Primary Zone ◽  
Wide Range ◽  
Partially Premixed

A methodology is presented in this paper on the modeling of NOx formation in diffusion flame combustors where both droplet burning and partially premixed reaction proceed simultaneously. The model simulates various combustion zones with an arrangement of reactors that are coupled with a detailed chemical reaction scheme. In this model, the primary zone of the combustor comprises a reactor representing contribution from droplet burning under stoichiometric conditions and a mixing reactor that provides additional air or fuel to the primary zone. The additional flow allows forming a fuel vapor/air mixture distribution that reflects the unmixedness nature of the fuel injection process. Expressions to estimate the extent of deviation in fuel/air ratios from the mean value, and the duration of droplet burning under stoichiometric conditions were derived. The derivation of the expressions utilized a data base obtained in a parametric study performed using a conventional gas turbine combustor where the primary zone equivalence ratio varied over a wide range of operation. The application of the developed model to a production combustor indicated that most of the NOx produced under the engine takeoff mode occurred in the primary as well as the intermediate regions. The delay in NOx formation is attributed to the operation of the primary zone under fuel rich conditions resulting in a less favorable condition for NOx formation. The residence time for droplet burning increased with a decrease in engine power. The lower primary zone gas temperature that limits the spray evaporation process coupled with the leaner primary zone mixtures under idle and low power modes increases the NOx contribution from liquid droplet combustion in diffusion flames. Good agreement was achieved between the measured and calculated NOx emissions for the production combustor. This indicates that the simulation of the diffusion flame by a combined droplet burning and fuel vapor/air mixture distribution offers a promising approach for estimating NOx emissions in combustors, in particular for those with significant deviation from traditional stoichiometry in the primary combustion zone.

Predictions of NOx Formation Under Combined Droplet and Partially Premixed Reaction of Diffusion Flame Combustors

1999 ◽  
Author(s):  
Nader K. Rizk ◽  
Ju S. Chin ◽  
Andre W. Marshall ◽  
Mohan K. Razdan
Keyword(s):  
Diffusion Flame ◽  
Liquid Droplet ◽  
Mixture Distribution ◽  
Fuel Vapor ◽  
Nox Emissions ◽  
Gas Temperature ◽  
Nox Formation ◽  
Primary Zone ◽  
Wide Range ◽  
Partially Premixed

A methodology is presented in this paper on the modeling of NOx formation in diffusion flame combustors where both droplet burning and partially premixed reaction proceed simultaneously. The model simulates various combustion zones with an arrangement of reactors that are coupled with a detailed chemical reaction scheme. In this model, the primary zone of the combustor comprises a reactor representing contribution from droplet burning under stoichiometric conditions and a mixing reactor that provides additional air or fuel to the primary zone. The additional flow allows forming a fuel vapor/air mixture distribution that reflects the unmixedness nature of the fuel injection process. Expressions to estimate the extent of deviation in fuel/air ratios from the mean value, and the duration of droplet burning under stoichiometric conditions were derived. The derivation of the expressions utilized a data base obtained in a parametric study performed using a conventional gas turbine combustor where the primary zone equivalence ratio varied over a wide range of operation. The application of the developed model to a production combustor indicated that most of the NOx produced under the engine takeoff mode occurred in the primary as well as the intermediate regions. The delay in NOx formation is attributed to the operation of the primary zone under fuel rich conditions resulting in a less favorable condition for NOx formation. The residence time for droplet burning increased with a decrease in engine power. The lower primary zone gas temperature that limits the spray evaporation process coupled with the leaner primary zone mixtures under idle and low power modes increases the NOx contribution from liquid droplet combustion in diffusion flames. Good agreement was achieved between the measured and calculated NOx emissions for the production combustor. This indicates that the simulation of the diffusion flame by a combined droplet burning and fuel vapor/air mixture distribution offers a promising approach for estimating NOx emissions in combustors, in particular for those with significant deviation from traditional stoichiometry in the primary combustion zone.

Low NOx Emission From an Ambient Pressure Diffusion Flame Fired Gas Turbine Cycle (APGC)

2002 ◽  
Vol 125 (1) ◽  
pp. 46-50
Author(s):  
G. Vermes ◽  
L. E. Barta ◽  
J. M. Bee´r
Keyword(s):  
Gas Turbine ◽  
Diffusion Flame ◽  
Power Plants ◽  
Ambient Pressure ◽  
Nox Emission ◽  
Heat Extraction ◽  
Operating Pressure ◽  
Nox Formation ◽  
Experimental Development ◽  
Gas Turbine Cycle

The prospects of reduced NOx emission, improved efficiency, stable, and oscillation-free combustion, and reduced construction costs achieved by an “Inverted Brayton Cycle” applied to midsize (0.5 to 5.0 MWe) power plants are discussed. In this cycle, the combustion products of an atmospheric pressure combustor are expanded in the gas turbine to subatmospheric pressure and following heat extraction are compressed back to slightly above the atmospheric, sufficient to enable a controlled fraction of the exhaust gas to be recirculated to the combustor. Due to the larger volume flow rate of the gas, the polytropic efficiency of both the turbine and compressor of this small machine is increased. Because of the low operating pressure and flue gas recirculation, both of which are instrumental to low NOx formation, the combustor can be operated in the diffusion flame mode; this, on the other hand, assures good flame stability and oscillation-free combustion over wide ranges of the operating variables. For the task of obtaining very low NOx formation, the well-tested multi annular swirl burner (MASB) is chosen. Recent computational and experimental development of the MASB by Siemens-Westinghouse as a topping combustor is discussed. It is shown that the MASB operated in rich-quench-lean mode is capable of single-digit NOx emission. The emissions are further lowered in the APGC by ambient pressure combustion, and by the injection of the recirculated gas in the quench zone of the combustor. Results of a computational optimization study of the ambient pressure gas turbine cycle (APGC) are presented.

scholarly journals Influence of DC Electric Field on the Propane-Air Diffusion Flames and NOx Formation

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5745
Author(s):  
Sang-Min Kim ◽  
Kyeong-Soo Han ◽  
Seung-Wook Baek
Keyword(s):  
Electric Field ◽  
Diffusion Flame ◽  
Diffusion Flames ◽  
Combustion Process ◽  
Flame Length ◽  
Nox Emission ◽  
Nox Formation ◽  
Dc Electric Field ◽  
Air Diffusion ◽  
Reduction Percentage

The aim of this research is to investigate the effects of a direct current (DC) electric field on the combustion behavior of a co-flow propane diffusion flame. The flame length and NOx emission were observed and measured. The electric field enhances the combustion process of propane diffusion flame by causing the movement of ions and molecules in the flame, resulting in a change in the shape of the flame. The flame heights decrease with an increase in the applied voltage and polarity, a more dominant effect to be observed with a positive DC electric field. However, for the applied negative polarity, the inner-cone of the propane diffusion flame is shifted by the electric field. Drastic reduction in the NOx emission is observed with an increase in the applied DC voltage and polarity. In the existing system, the reduction percentage of NOx is within the range of 55 to 78%.

NOx Reduction in Gas Turbine Combustors With Compact Non-Premixed Flame Front

2014 ◽  
Author(s):  
V. V. Tsatiashvili ◽  
V. G. Avgustinovich
Keyword(s):  
Flame Front ◽  
Gas Turbine ◽  
Nox Reduction ◽  
Premixed Flame ◽  
Nox Emission ◽  
Nox Formation ◽  
New Approach ◽  
Index Reduction ◽  
Primary Zone ◽  
Low Emission

This paper represents results of R&D efforts towards reducing a bypass turbofan engine NOx emission by 45 % compared with CAEP/6 to meet the ICAO NOx emission goal of 2020. To achieve ICAO NOx technology goal, a new approach is used based on the NOx emission reduction in combustors with non-premixed combustion well proved in operation. The new approach is represented by structured system of low emission combustion principles — a concept of combustor featuring compact non-premixed flame (CNPF). The essence of CNPF concept is in suppression of volume and surface NOx formation sources by flame front blocking in liner primary zone and by increasing of fuel effective burning rate. The paper represents the development of concept up to and including the 4th technology maturity level. It demonstrates CNPF concept independence and interaction with other up-to-date gas turbine low emission concepts. The paper indicates comparison of rig test results between in-service combustor and CNPF adopted combustors carried out on a single liner. A CNPF adopted combustor shows NOx emission index reduction by 35 …47 % at take-off engine conditions. Preliminary estimation shows that it is possible to reach the ICAO goal for NOx emission level of 2020.

NOx emission from high-temperature air/methane counterflow diffusion flame

2002 ◽  
Vol 41 (7) ◽  
pp. 693-698 ◽  
Author(s):  
Ryugo Fuse ◽  
Hideaki Kobayashi ◽  
Yiguang Ju ◽  
Kaoru Maruta ◽  
Takashi Niioka
Keyword(s):  
High Temperature ◽  
Diffusion Flame ◽  
Nox Emission ◽  
Counterflow Diffusion Flame
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