CFD Analysis of NOx Emissions of a Natural Gas Lean Premixed Burner for Heavy Duty Gas Turbine

As government regulations become increasingly strict with regards to combustion pollutant emissions, new gas turbine combustor designs must produce lower NOx while also maintaining acceptable combustor operability. The design and implementation of an efficient fuel/air premixer is paramount to achieving low emissions. Options for improving the design of a natural gas fired heavy-duty gas turbine partially premixed fuel nozzle have been considered in the current study. In particular, the study focused on fuel injection and pilot/main interaction at high pressure and high inlet temperature. NOx emissions results have been reported and analyzed for a baseline nozzle first. Available experience is shared in this paper in the form of a NOx correlative model, giving evidence of the consistency of current results with past campaigns. Subsequently, new fuel nozzle premixer designs have been investigated and compared, mainly in terms of NOx emissions performance. The operating range of investigation has been preliminarily checked by means of a flame stability assessment. Adequate margin to lean blow out and thermo-acoustic instabilities onset has been found while also maintaining acceptable CO emissions. NOx emission data were collected over a variety of fuel/air ratios and pilot/main splits for all the fuel nozzle configurations. Results clearly indicated the most effective design option in reducing NOx. In addition, the impact of each design modification has been quantified and the baseline correlative NOx emissions model calibrated to describe the new fuel nozzles behavior. Effect of inlet air pressure has been evaluated and included in the models, allowing the extensive use of less costly reduced pressure test campaigns hereafter. Although the observed effect of combustor pressure drop on NOx is not dominant for this particular fuel nozzle, sensitivity has been performed to consolidate gathered experience and to make the model able to evaluate even small design changes affecting pressure drop.

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Development of a Natural Gas-Fired, Ultra-Low NOx Can Combustor for an 800 KW Gas Turbine

Volume 3: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations ◽

10.1115/91-gt-303 ◽

1991 ◽

Cited By ~ 4

Author(s):

K. O. Smith ◽

A. C. Holsapple ◽

H. K. Mak ◽

L. Watkins

Keyword(s):

Natural Gas ◽

Gas Turbine ◽

Premixed Combustion ◽

Experimental Results ◽

Nox Emissions ◽

Variable Geometry ◽

Lean Premixed Combustion ◽

Full Load ◽

Primary Zone ◽

Lean Premixed

The experimental results from the rig testing of an ultra-low NOx, natural gas-fired combustor for an 800 to 1000 kw gas turbine are presented. The combustor employed lean-premixed combustion to reduce NOx emissions and variable geometry to extend the range over which low emissions were obtained. Testing was conducted using natural gas and methanol. Testing at combustor pressures up to 6 atmospheres showed that ultra-low NOx emissions could be achieved from full load down to approximately 70% load through the combination of lean-premixed combustion and variable primary zone airflow.

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Combustion Instabilities Damping System Development for Dry Low NOx Emissions Operability Enhancement of a Heavy-Duty Gas Turbine

Volume 4B: Combustion, Fuels, and Emissions ◽

10.1115/gt2019-91246 ◽

2019 ◽

Author(s):

Matteo Cerutti ◽

Nicola Giannini ◽

Bruno Schuermans ◽

Riccardo Brenci ◽

Alessandro Marini ◽

...

Keyword(s):

Growth Rate ◽

Gas Turbine ◽

Growth Rates ◽

Fine Tuning ◽

Optimized Design ◽

Nox Emissions ◽

Preliminary Design ◽

Heavy Duty ◽

Wide Range ◽

Heavy Duty Gas Turbine

Abstract This paper describes the development phases of a damping system for combustion instability reduction in an annular type combustor for heavy-duty gas turbine applications. As reported by the authors in a previous paper, the full scale annular test rig allowed for an extensive characterization of the combustor with realistic acoustic boundaries at engine-relevant conditions. Emissions and operability assessment over a wide range of load conditions was performed, allowing the evaluation of the response of the system near the thermo-acoustic instability onset. The instability is quantified by its acoustic growth rate. This quantity is a crucial input in the design process of dampers. A methodology has been used to extract these growth rates form measured pulsation data. Experimentally determined growth rates have been evaluated for different fuel flow rate split between the main and the pilot injections, providing input to dampers preliminary design. Given current combustor architecture constraints, a first attempt configuration has been proposed and performances evaluated in the full annular rig. Dampers have been equipped with dynamic sensors and thermocouples with the purpose of measuring the growth rate abatement and the consequent NOx emissions reduction. A dedicated numerical toolbox, in-house developed by GE Power, has been used for both dampers preliminary design and growth rate reduction evaluation. Fine tuning of dampers elements as well as design assumptions adjustments required additional experimental evaluations and design iterations. Encouraged by the successful test in the concept phase, an optimized design for engine implementation was defined, that featured a significant increased damper volume, involving combustor parts re-design. The optimized configuration was finally tested in full annular rig and results demonstrated an important enhancement of operability while maintaining NOx emissions below the target levels.

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Experimental and Numerical Characterization of Lean Hydrogen Combustion in a Premix Burner Prototype

Volume 2: Combustion, Fuels and Emissions, Parts A and B ◽

10.1115/gt2011-45623 ◽

2011 ◽

Cited By ~ 3

Author(s):

Iarno Brunetti ◽

Giovanni Riccio ◽

Nicola Rossi ◽

Alessandro Cappelletti ◽

Lucia Bonelli ◽

...

Keyword(s):

Natural Gas ◽

Gas Turbine ◽

Hydrogen Content ◽

Premixed Combustion ◽

Nox Emissions ◽

Cfd Model ◽

Air Velocity ◽

Lean Premixed Combustion ◽

Lean Premixed

The use of hydrogen as derived fuel for low emission gas turbine is a crucial issue of clean coal technology power plant based on IGCC (Integrated Gasification Combined Cycle) technology. Control of NOx emissions in gas turbines supplied by natural gas is effectively achieved by lean premixed combustion technology; conversely, its application to NOx emission reduction in high hydrogen content fuels is not a reliable practice yet. Since the hydrogen premixed flame is featured by considerably higher flame speed than natural gas, very high air velocity values are required to prevent flash-back phenomena, with obvious negative repercussions on combustor pressure drop. In this context, the characterization of hydrogen lean premixed combustion via experimental and modeling analysis has a special interest for the development of hydrogen low NOx combustors. This paper describes the experimental and numerical investigations carried-out on a lean premixed burner prototype supplied by methane-hydrogen mixture with an hydrogen content up to 100%. The experimental activities were performed with the aim to collect practical data about the effect of the hydrogen content in the fuel on combustion parameters as: air velocity flash-back limit, heat release distribution, NOx emissions. This preliminary data set represents the starting point for a more ambitious project which foresees the upgrading of the hydrogen gas turbine combustor installed by ENEL in Fusina (Italy). The same data will be used also for building a computational fluid dynamic (CFD) model usable for assisting the design of the upgraded combustor. Starting from an existing heavy-duty gas turbine burner, a burner prototype was designed by means of CFD modeling and hot-wire measurements. The geometry of the new premixer was defined in order to control turbulent phenomena that could promote the flame moving-back into the duct, to increase the premixer outlet velocity and to produce a stable central recirculation zone in front of the burner. The burner prototype was then investigated during a test campaign performed at the ENEL’s TAO test facility in Livorno (Italy) which allows combustion test at atmospheric pressure with application of optical diagnostic techniques. In-flame temperature profiles, pollutant emissions and OH* chemiluminescence were measured over a wide range of the main operating parameters for three fuels with different hydrogen content (0, 75% and 100% by vol.). Flame control on burner prototype fired by pure hydrogen was achieved by managing both the premixing degree and the air discharge velocity, affecting the NOx emissions and combustor pressure losses respectively. A CFD model of the above-mentioned combustion test rig was developed with the aim to validate the model prediction capabilities and to help the experimental data analysis. Detailed simulations, performed by a CFD 3-D RANS commercial code, were focused on air/fuel mixing process, temperature field, flame position and NOx emission estimation.

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A Comparative Analysis of Single Nozzle and Multiple Nozzles Arrangements for Syngas Combustion in Heavy Duty Gas Turbine

Journal of Energy Resources Technology ◽

10.1115/1.4034232 ◽

2016 ◽

Vol 139 (2) ◽

Cited By ~ 1

Author(s):

Shi Liu ◽

Hong Yin ◽

Yan Xiong ◽

Xiaoqing Xiao

Keyword(s):

Natural Gas ◽

Gas Turbine ◽

Gas Turbines ◽

Combined Cycle ◽

Heavy Duty ◽

Gas Turbine Combustor ◽

Integrated Gasification Combined Cycle ◽

Wide Range ◽

Heavy Duty Gas Turbine ◽

Integrated Gasification

Heavy duty gas turbines are the core components in the integrated gasification combined cycle (IGCC) system. Different from the conventional fuel for gas turbine such as natural gas and light diesel, the combustible component acquired from the IGCC system is hydrogen-rich syngas fuel. It is important to modify the original gas turbine combustor or redesign a new combustor for syngas application since the fuel properties are featured with the wide range hydrogen and carbon monoxide mixture. First, one heavy duty gas turbine combustor which adopts natural gas and light diesel was selected as the original type. The redesign work mainly focused on the combustor head and nozzle arrangements. This paper investigated two feasible combustor arrangements for the syngas utilization including single nozzle and multiple nozzles. Numerical simulations are conducted to compare the flow field, temperature field, composition distributions, and overall performance of the two schemes. The obtained results show that the flow structure of the multiple nozzles scheme is better and the temperature distribution inside the combustor is more uniform, and the total pressure recovery is higher than the single nozzle scheme. Through the full scale test rig verification, the combustor redesign with multiple nozzles scheme is acceptable under middle and high pressure combustion test conditions. Besides, the numerical computations generally match with the experimental results.

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Syngas Burner Optimization for Fuelling a Heavy Duty Gas Turbine With Various Syngas Blends

Volume 2: Aircraft Engine; Ceramics; Coal, Biomass and Alternative Fuels; Controls, Diagnostics and Instrumentation; Environmental and Regulatory Affairs ◽

10.1115/gt2006-90761 ◽

2006 ◽

Cited By ~ 1

Author(s):

Federico Bonzani

Keyword(s):

Power Plant ◽

Natural Gas ◽

Gas Turbine ◽

Heavy Duty ◽

Main Aspect ◽

The Past ◽

Variable Quantity ◽

Maximum Quantity ◽

Heavy Duty Gas Turbine ◽

Base Load

The IGCC power plant of Ferrera Erbognone will be the first real commercial power plant in Italy to be operated without taking into account the high benefits once available according to the national law (CIP6/1992) specifically dealing with recovery fuel usage alternative to natural gas. The syngas will be provided by the nearby refinery using tar as main feedstock. Furthermore, according to the demands of the refinery it will be possible in the gasifier island to separate hydrogen in variable quantity from the syngas thus giving a high variability composition as output fuel. Also, if the maximum quantity of hydrogen will be separated, an integration with natural gas will be performed in order to get the maximum power output of the power plant. As a consequence, the syngas burner has been designed taking into account all the fuel characteristics depending on the different composition carried out. According to these, the burner has been optimised in order to fit the various syngas blends to be fuelled when running the engine. In order to verify the modifications carried out the burner has been tested both at atmospheric and full engine conditions since the NOx requirements for this project are the more stringent experienced with respect to the past projects (NOx to be below 25 ppm). During these test the main aspect to be in investigated have been: a) Minimum load when feeding the gas turbine with syngas. b) NOx emission from 60% load up to base load. c) Change over from natural gas to syngas and vice versa. The tests have been performed successfully: commissioning on site will start on November 2005. The paper describe the design and the testing phase highlighting the main features of the burner and the fuel system with respect to the plant requirements.

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Modeling of Natural Gas Composition Effect on Low NOX Burners Operation in Heavy Duty Gas Turbine

10.1115/1.0002772v ◽

2021 ◽

Author(s):

Serena Romano ◽

Roberto Meloni ◽

Pier Carlo Nassini ◽

Antonio Andreini ◽

Giovanni Riccio

Keyword(s):

Natural Gas ◽

Gas Turbine ◽

Gas Composition ◽

Composition Effect ◽

Heavy Duty ◽

Heavy Duty Gas Turbine

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Chemical Kinetic Modeling of Ignition and Emissions From Natural Gas and LNG Fueled Gas Turbines

Volume 2: Combustion, Fuels and Emissions, Parts A and B ◽

10.1115/gt2012-69902 ◽

2012 ◽

Cited By ~ 4

Author(s):

P. Gokulakrishnan ◽

C. C. Fuller ◽

R. G. Joklik ◽

M. S. Klassen

Keyword(s):

Natural Gas ◽

Gas Turbine ◽

Gas Turbines ◽

Chemical Kinetic ◽

Higher Order ◽

Premixed Combustion ◽

Nox Emissions ◽

Lean Premixed Combustion ◽

Lean Premixed ◽

Combustion Systems

Single digit NOx emission targets as part of gas turbine design criteria require highly accurate modeling of the various NOx formation pathways. The concept of lean, premixed combustion is adopted in various gas turbine combustor designs, which achieves lower NOx levels by primarily lowering the flame temperature. At these conditions, the post-flame thermal-NOx pathway contribution to the total NOx can be relatively small compared to that from the prompt-NOx and the N2O-route, which are enhanced by the super-equilibrium radical pathway at the flame front. In addition, new sources of natural gas fuel (e.g., imported LNG) with widely varying chemical compositions including higher order hydrocarbon components, impact flame stability, lean blow-out limits and emissions in existing lean premixed combustion systems. Also, the presence of higher order hydrocarbons can increase the risk of flashback induced by autoignition in the premixing section of the combustor. In this work a detailed chemical kinetic model was developed for natural gas fuels that consist of CH4, C2H6, C3H8, nC4H10, iC4H10, and small amounts of nC5H12, iC5H12 and nC6H14 in order to predict ignition behavior at typical gas turbine premixing conditions and to predict CO and NOx emissions at lean premixed combustion conditions. The model was validated for different NOx-pathways using low and high pressure laminar premixed flame data. The model was also extended to include a vitiated kinetic scheme to account for the influence of exhaust gas recirculation on fuel oxidation. The model was employed in a chemical reactor network to simulate a laboratory scale lean premixed combustion system to predict CO and NOx. The current kinetic mechanism demonstrates good predictive capability for NOx emissions at lower temperatures typical of practical lean premixed combustion systems.

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Effect of Natural Gas Composition on Low NOx Burners Operation in Heavy Duty Gas Turbine

Volume 4A: Combustion, Fuels, and Emissions ◽

10.1115/gt2019-90903 ◽

2019 ◽

Author(s):

Serena Romano ◽

Matteo Cerutti ◽

Giovanni Riccio ◽

Antonio Andreini ◽

Christian Romano

Keyword(s):

Natural Gas ◽

Gas Turbine ◽

Operating Conditions ◽

Fuel Composition ◽

Gas Composition ◽

Heavy Duty ◽

Wide Range ◽

Annular Combustor ◽

Heavy Duty Gas Turbine ◽

The Impact

Abstract Development of lean-premixed combustion technology with low emissions and stable operation in an increasingly wide range of operating conditions requires a deep understanding of the mechanisms that affect the combustion performance or even the operability of the entire gas turbine. Due to the relative wide range of natural gas composition supplies and the increased demand from Oil&Gas customers to burn unprocessed gas as well as LNG with notable higher hydrocarbons (C2+) content; the impact on gas turbine operability and combustion related aspects has been matter of several studies. In this paper, results of experimental test campaign of an annular combustor for heavy-duty gas turbine are presented with focus on the effect of fuel composition on both emissions and flame stability. Test campaign involved two different facilities, a full annular combustor rig and a full-scale prototype engine fed with different fuel mixtures of natural gas with small to moderate C2H6 content. Emissions trends and blowout for several operating conditions and burner configurations have been analyzed. Modifications to the burner geometry and fuel injection optimization have shown to be able to reach a good trade-off while keeping low NOx emissions in stable operating conditions for varying fuel composition.

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