scholarly journals Study on Unsteady NOx Formation Characteristics in Diffusion Flame and Verification of Combination Method Predicting NOx Emission of Turbulent Flame.

2003 ◽  
Vol 69 (678) ◽  
pp. 453-460
Author(s):  
Akihiro SHIMIZU ◽  
Hiroshi YAMASHITA ◽  
Yoshinobu TAKAISHI ◽  
Daiqing ZHAO
Keyword(s):  
Diffusion Flame ◽  
Turbulent Flame ◽  
Nox Emission ◽  
Combination Method ◽  
Nox Formation

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.

A Novel Les-Based Process for NOx Emission Assessment in a Premixed Swirl Stabilized Combustion System

2021 ◽  
Author(s):  
Roberto Meloni ◽  
Antonio Andreini ◽  
Pier Carlo Nassini
Keyword(s):  
Turbulent Flame ◽  
Nox Emission ◽  
Percentage Error ◽  
Nox Formation ◽  
Fuel Gas ◽  
Turbulent Flame Speed ◽  
Eddy Simulation ◽  
Annular Combustor ◽  
Swirl Stabilized Combustion ◽  
The Impact

Abstract This paper presents a new CFD approach for the assessment of the NOx emission. The methodology is validated against the experimental data of a heavy-duty gas turbine annular combustor. Since the NOx formation involves time scales that are different from the fuel oxidation time, the present work defines the transport equation source terms for NOx on the basis of a dedicate NOx-Damköhler number. The latter parameter allows to properly distinguish the "in-flame" contribution from the "post-flame" one. While the former is a mix of several mechanisms (prompt, N2O-pathway, thermal), the latter is dominated by the thermal contribution. The validation phase is developed in a Large-Eddy Simulation (LES) framework where the Extended Turbulent Flame Speed model is implemented to consider the influence of both heat loss and strain rate on the progress variable source term. The accuracy of the model against the most important operability parameters of the combustor is verified. A strong focus on the fuel composition effect onto NOx is presented as well. For any simulated operating condition, the present methodology is able to provide a limited percentage error if compared with the data, considering also different combustion regimes. Leveraging this alignment, the last portion of the paper is dedicated to a detailed post processing highlighting the role of some key factors on to NOx formation. In particular, the focus will be dedicated to the impact of the fuel gas composition and the pilot split.

A Novel LES-Based Process for NOx Emission Assessment in a Premixed Swirl Stabilized Combustion System

2021 ◽  
Author(s):  
R. Meloni ◽  
A. Andreini ◽  
P. C. Nassini
Keyword(s):  
Turbulent Flame ◽  
Nox Emission ◽  
Percentage Error ◽  
Nox Formation ◽  
Fuel Gas ◽  
Turbulent Flame Speed ◽  
Eddy Simulation ◽  
Annular Combustor ◽  
Swirl Stabilized Combustion ◽  
The Impact

Abstract This paper presents a new CFD approach for the assessment of the NOx emission. The methodology is validated against the experimental data of a heavy-duty gas turbine annular combustor. Since the NOx formation involves time scales that are different from the fuel oxidation time, the present work defines the transport equation source terms for NOx on the basis of a dedicate NOx-Damköhler number. The latter parameter allows to properly distinguish the “in-flame” contribution from the “post-flame” one. While the former is a mix of several mechanisms (prompt, N2O-pathway thermal), the latter is dominated by the thermal contribution. The validation phase is developed in a Large-Eddy Simulation (LES) framework where the Extended Turbulent Flame Speed model is implemented to consider the influence of both heat loss and strain rate on the progress variable source term. The accuracy of the model against the most important operability parameters of the combustor is verified. A strong focus on the fuel composition effect onto NOx is presented as well. For any simulated operating condition, the present methodology is able to provide a limited percentage error if compared with the data, considering also different combustion regimes. Leveraging this alignment, the last portion of the paper is dedicated to a detailed post processing highlighting the role of some key factors on to NOx formation. In particular, the focus will be dedicated to the impact of the fuel gas composition and the pilot split.

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 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

Effects of Burner Interaction on NOx Emission From Swirl Premix Burner in a Gas Turbine Combustor

2014 ◽  
Author(s):  
Cheon Hyeon Cho ◽  
Chae Hoon Sohn ◽  
Ju Hyeong Cho ◽  
Han Seok Kim
Keyword(s):  
Gas Turbine ◽  
Nox Emission ◽  
Gas Turbine Combustor ◽  
Step Size ◽  
Flow Temperature ◽  
Nox Formation ◽  
Air Stream ◽  
Flow Interactions ◽  
Model Chamber ◽  
Wall Interaction

Flame interaction between neighboring burners in a gas turbine combustor is investigated numerically for pursuit of its effect on NOx emission from the burners. In a model chamber or liner, EV burners with double cone are installed. Two burners with the same rotating direction of air stream are adopted and the distance between them is variable from 74.2 mm to 222.6 mm by the step size of 37.1 mm. Gaseous methane and air are adopted as fuel and oxidizer, respectively. From steady-state numerical analyses, flow, temperature, and NO concentration fields are calculated in all computational cases to find their correlation with NOx formation. NOx emission is evaluated at the exit of the model chamber with two burners as a function of burner distance and compared with that from a single burner. In all cases of two-burner calculations, NOx emission is higher than that of a single burner, which results from flow interactions between neighboring burners as well as between a burner and a liner wall. NOx emission is affected significantly by flow and flame interactions between them and strongly depends on burner distance. Burner interaction is divided into two regimes of a burner-burner interaction and a burner-wall interaction depending on the distance. In the former regime, NOx emission is reduced as flame interaction between burners is enhanced and in the latter regime, it is also reduced as interaction between the burner and the liner wall is enhanced.

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