Flame Stabilization and Emission Characteristics of a Prototype Gas Turbine Burner at Atmospheric Conditions

2016 ◽  
Author(s):  
Atanu Kundu ◽  
Jens Klingmann ◽  
Arman Ahamed Subash ◽  
Robert Collin
Keyword(s):  
Gas Turbine ◽  
Reaction Zone ◽  
Vector Fields ◽  
Thermal Power ◽  
Flame Structure ◽  
Flame Temperature ◽  
Flame Stabilization ◽  
Atmospheric Conditions ◽  
Pilot Fuel ◽  
Co Emission

In the present work, a downscaled prototype 4th generation Dry Low Emission gas turbine (SGT-750) burner (designed and manufactured by Siemens Industrial Turbomachinery AB, Sweden) was investigated using an atmospheric experimental facility. The primary purpose of the research is to analyze flame stability and emission capability of the burner. OH Planar Laser-Induced Fluorescence (OH-PLIF), and chemiluminescence imaging were performed to characterize the flame structure and location. From the OH-PLIF images, the reaction zone and post flame region could be identified clearly. The chemiluminescence images provide an estimation of the overall heat release from the secondary combustion zone inside the Quarl. Emission was measured using a water-cooled emission probe, placed at the exit of the combustor to sample NOx and CO concentrations. The global equivalence ratio (Φ) was varied from rich to lean limit (flame temperature change from 1950 K to 1570 K) for understanding the stable and instable reaction zones inside the Quarl. Total thermal power was varied from 70 kW to 140 kW by changing global Φ and burner throat velocity (60 to 80 m/s). Near the lean blowout (LBO) event (at global Φ ∼ 0.4), instability of reaction zone is revealed from the flame images. Incorrect modulation of Pilot and RPL fuel splits show instable flame. Flame instability mitigation was possible using higher amount of RPL and Pilot fuel (trade-off with emission performance). The main flame LBO margin was extended by applying higher Pilot fuel and using higher preheat air temperature. Numerical analysis was carried out using Fluent to understand the scalar and vector fields. A basic chemical reactor network model was developed to predict the NOx and CO emission with experimental results. NOx emission prediction showed good agreement with experiment; whereas the model is failed to capture accurate CO emission in the lean operating points.

Analysis of Water–Fuel Ratio Variation in a Gas Turbine With a Wet-Compressor System by Change in Fuel Composition

2017 ◽  
Vol 140 (5) ◽  
Author(s):  
Yonatan Cadavid ◽  
Andres Amell ◽  
Juan Alzate ◽  
Gerjan Bermejo ◽  
Gustavo A. Ebratt
Keyword(s):  
Gas Turbine ◽  
Burning Velocity ◽  
Thermal Power ◽  
Flame Temperature ◽  
Fuel Composition ◽  
Nox Formation ◽  
Gaseous Hydrocarbon ◽  
Power Generators ◽  
Fuel Ratio ◽  
Combustion Properties

The wet compressor (WC) has become a reliable way to reduce gas emissions and increase gas turbine efficiency. However, fuel source diversification in the short and medium terms presents a challenge for gas turbine operators to know how the WC will respond to changes in fuel composition. For this study, we assessed the operational data of two thermal power generators, with outputs of 610 MW and 300 MW, in Colombia. The purpose was to determine the maximum amount of water that can be added into a gas turbine with a WC system, as well as how the NOx/CO emissions vary due to changes in fuel composition. The combustion properties of different gaseous hydrocarbon mixtures at wet conditions did not vary significantly from each other—except for the laminar burning velocity. It was found that the fuel/air equivalence ratio in the turbine reduced with lower CH4 content in the fuel. Less water can be added to the turbine with leaner combustion; the water/fuel ratio was decreased over the range of 1.4–0.4 for the studied case. The limit is mainly due to a reduction in flame temperature and major risk of lean blowout (LBO) or dynamic instabilities. A hybrid reaction mechanism was created from GRI-MECH 3.0 and NGIII to model hydrocarbons up to C5 with NOx formation. The model was validated with experimental results published previously in literature. Finally, the effect of atmospheric water in the premixed combustion was analyzed and explained.

Effect of Fuel Stage Proportion on Flame Position in an Internally-Staged Combustor

2020 ◽  
Author(s):  
Tiezheng Zhao ◽  
Xiao Liu ◽  
Hongtao Zheng ◽  
Zhihao Zhang ◽  
Jialong Yang ◽  
...  
Keyword(s):  
Turbulent Flame ◽  
Flame Temperature ◽  
Prediction Method ◽  
Combustion Characteristics ◽  
Turbulent Flame Speed ◽  
Pilot Fuel ◽  
High Temperature Area ◽  
Incomplete Reaction ◽  
Co Emission ◽  
Flame Position

Abstract To study the effect of fuel stage proportion on flame position and combustion characteristics of the internally-staged combustor, a detailed numerical investigation is performed in the present paper. The prediction method of flame position is established by analyzing the variations of the distribution of intermediate components and the turbulent flame speed. Meanwhile, the flame position is simulated to verify the accuracy of the prediction method. It is demonstrated that the flame position prediction model established in this paper can accurately predict the flame position under different fuel stage proportions. On this basis, special attention is paid to analyze the variation of velocity field, temperature field, distribution of intermediate components and emissions under different fuel stage proportions. As the proportion of pilot fuel stage increases slightly, the mass fraction of fuel at the combustor dome increases. In addition, the combustion characteristics change significantly with the increase in the proportion of pilot stage fuels. The flame moves downstream and the high temperature area increases as the proportion of pilot fuel increases. In particular, when the proportion of pilot stage reaches 3%, the highest flame temperature is generated due to the most concentrated reaction area, resulting in the largest emission of NOx. At the same time, due to the most complete reaction, the minimum CO emission is produced. When the proportion of pilot fuel stage reaches 1%, the NOx emission is the lowest, and the highest CO emission is generated due to the incomplete reaction.

Effects of Pilot Fuel and Liner Cooling on the Flame Structure in a Full Scale Swirl-Stabilized Combustion Setup

2009 ◽  
Author(s):  
Jens Fa¨rber ◽  
Rainer Koch ◽  
Hans-Jo¨rg Bauer ◽  
Matthias Hase ◽  
Werner Krebs
Keyword(s):  
Combustion Chamber ◽  
Fuel Injection ◽  
Flame Structure ◽  
Cone Angle ◽  
Flow Patterns ◽  
Flame Stabilization ◽  
Operating Conditions ◽  
Combustion Noise ◽  
Pilot Fuel ◽  
Combustor Liner

The flame structure and the limits of operation of a lean premixed swirl flame were experimentally investigated under piloted and non-piloted conditions. Flame stabilization and blow out limits are discussed with respect to pilot fuel injection and combustor liner cooling for lean operating conditions. Two distinctly different flow patterns are found to develop depending on piloting and liner cooling parameters. These flow patterns are characterized with respect to flame stability, blow out limits, combustion noise and emissions. The combustion system explored consists of a single burner similar to the burners used in Siemens annular combustion systems. The burner feeds a distinctively non-adiabatic combustion chamber operated with natural gas under atmospheric pressure. Liner cooling is mimicked by purely convective cooling and an additional flow of ‘leakage air’ injected into the combustion chamber. Both, this additional air flow and the pilot fuel ratio were found to have a strong influence on the flow structure and stability of the flame close to the lean blow off limit (LBO). It is shown by Laser Doppler Velocimetry (LDV) that the angle of the swirl cone is strongly affected by pilot fuel injection. Two distinct types of flow patterns are observed close to LBO in this large scale setup: While non-piloted flames exhibit tight cone angles and small inner recirculation zones (IRZ), sufficient piloting results in a wide cone angle and a large IRZ. Only in the latter case, the main flow becomes attached to the combustor liner. Flame structures deduced from flow fields and CH-Chemiluminescence images depend on both the pilot fuel injection and liner cooling.

Impact of Internal Entrainment on High Intensity Distributed Combustion

2015 ◽  
Author(s):  
Ahmed E. E. Khalil ◽  
Ashwani K. Gupta
Keyword(s):  
Carbon Dioxide ◽  
Gas Turbine ◽  
Oxygen Concentration ◽  
High Intensity ◽  
Flame Structure ◽  
Flame Stabilization ◽  
Low Oxygen ◽  
Gas Turbine Combustors ◽  
Reactive Gases ◽  
The Impact

Colorless Distributed Combustion (also referred to as CDC) has been shown to provide ultra-low emissions and enhanced performance of high intensity gas turbine combustors. To achieve distributed combustion, the flowfield needs to be tailored for adequate mixing between reactants and hot reactive species from within the combustor to result in high temperature low oxygen concentration environment prior to ignition. Such reaction distribution results in uniform thermal field and also eliminates any hot spots for mitigating NOx emission. Though CDC have been extensively studied using a variety of geometries, heat release intensities, and fuels, the role of internally recirculated hot reactive gases needs to be further investigated and quantified. In this paper, the impact of internal entrainment of reactive gases on flame structure and behavior is investigated with focus on fostering distributed combustion and providing guidelines for designing future gas turbine combustors operating in distributed combustion mode. To simulate the recirculated gases from within the combustor, a mixture of nitrogen and carbon dioxide is introduced to the air stream prior to mixing with fuel and subsequent combustion. Increase in the amounts of nitrogen and carbon dioxide (simulating increased entrainment), led to volume distributed reaction over a larger volume in the combustor with enhanced and uniform distribution of the OH* chemiluminescence intensity. At the same time, the bluish flame stabilized by the swirler is replaced with a more uniform almost invisible bluish flame. The increased recirculation also reflected on the pollutants emission, where NO emissions were significantly decreased for the same amount of fuel burned. Lowering oxygen concentration from 21% to 15% (due to increased recirculation) resulted in 80∼90% reduction in NO with no impact on CO emission with sub PPM NO emission achieved at an equivalence ratio of 0.7. Flame stabilization at excess recirculation can be achieved using preheated nitrogen and carbon dioxide, achieving true distributed conditions with oxygen concentration below 13%.

Effects of CO2 dilution on combustion instabilities in dual premixed flames

2013 ◽  
Vol 227 (11) ◽  
pp. 2569-2581 ◽  
Author(s):  
Kangyeop Lee ◽  
Hyungmo Kim ◽  
Poomin Park ◽  
Sooseok Yang ◽  
Youngsung Ko
Keyword(s):  
Gas Turbine ◽  
Coupling Strength ◽  
Mass Fraction ◽  
Combustion Instability ◽  
Flame Structure ◽  
Fuel Mass ◽  
Gas Turbine Combustors ◽  
Low Emission ◽  
Pilot Fuel ◽  
Fuel Mass Fraction

There has been a rapid increase in the demand for biogas applications in recent years, and dry low NOx and dry low emission gas turbine combustors are promising platforms for such applications. Combustion instability is the most important drawback in dry low NOx gas turbine combustors and has, therefore, attracted considerable research interest lately. As a fundamental study towards the use of biogas in dry low NOx and dry low emission gas turbine combustors, this article investigates the influence of CO2 in surrogate biogas on combustion instability. Tests were conducted using a dry low NOx type, a dual lean premixed gas turbine combustor. For a dual flame with dual swirl, the pilot fuel mass fraction affects the flame structure, and the flame structure, in turn, determines the temperature distribution in the combustion chamber and the combustion instability. The effects of the pilot fuel mass fraction, which is an important parameter of the combustor, and the CO2 dilution rate, which is a major contributor of biogas combustion, on the combustion characteristics and instability are investigated through dynamic pressure signal and phase-resolved OH* images. Combustion instability decreases for higher CO2 dilution rates, whose effects depend on the pilot fuel mass fraction. The instability reaches its maximum at a pilot fuel mass fraction of 0.3. Tests confirm that combustion instability diminishes with CO2 dilution, as it reduces the perturbation in the heat emission, and the flame speed decreases resulting in a greater flame surface or volume. Further, investigation of the Rayleigh Index, which represents the coupling strength of the heat release fluctuation and the natural frequency, shows that CO2 dilution weakens the coupling strength, resulting in less combustion instability.

Effect of Strain Rate and Pressure on the Flame Structure and Emission Characteristics of Syngas Flames

2007 ◽  
Author(s):  
Sibendu Som ◽  
Anita I. Rami´rez ◽  
Jonathan Hagerdorn ◽  
Alexei Saveliev ◽  
Suresh K. Aggarwal
Keyword(s):  
Strain Rate ◽  
Reaction Zone ◽  
Laminar Flame ◽  
Flame Structure ◽  
Flame Temperature ◽  
Chemical Kinetic ◽  
No Production ◽  
Emission Characteristics ◽  
Strain Rates ◽  
Fundamental Understanding

Synthesis gas or “Syngas” is being recognized as a viable energy source worldwide, particularly for stationary power generation due to its wide flexibility in fuel sources. There are gaps in the fundamental understanding of syngas combustion and emissions characteristics, especially at elevated pressures, high strain rates and in more practical conditions. This paper presents a numerical and experimental investigation to gain fundamental understanding of combustion and emission characteristics of syngas with varying composition, pressure and strain rate. Two representative syngas fuel mixtures, 50% H2 / 50% CO and 5% H2 / 95% CO (% vol.), are chosen, three detailed chemical kinetic models are used namely, GRI 3.0, Davis et al. and Li et al. mechanisms. Davis et al. mechanism agrees best with the experimental data hence is used to simulate the partially premixed flame structures at all pressures. Results indicate that for the pressure range investigated, a typical double flame structure was observed characterized by a rich premixed reaction zone (RPZ) on the fuel side and a nonpremixed reaction zone (NPZ) at the oxidizer side nozzle with the stabilizing due to the H2 chemistry rather than the CO chemistry. Sensitivity analysis to mass burning rates for unstretched laminar flame shows that flames are more sensitive to H2 chemistry. For both representative mixtures an increase in pressure leads to a significant increase in NO due to increase in flame temperature. The emission index for these flames is also found to follow a similar behavior with pressure. Although flame temperatures were higher for flame A, total NO is lower for these flames due to increases in reburn characteristics. Thermal route dominates NO production while, prompt route is negligible. Experimental analysis on the stability of nonpremixed syngas/air flames showed that the flames were very stable for the range of strain rates investigated. At low strain rates it required 0.5% H2 to establish a stable flame.

Large Eddy Simulation and Experimental Analysis of Combustion Dynamics in a Gas Turbine Burner

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Daniel Moëll ◽  
Andreas Lantz ◽  
Karl Bengtson ◽  
Daniel Lörstad ◽  
Annika Lindholm ◽  
...  
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Flame Temperature ◽  
Cross Flow ◽  
Flame Stabilization ◽  
Large Eddy Simulations ◽  
Combustion Dynamics ◽  
Flamelet Generated Manifold ◽  
Large Eddy ◽  
Gas Turbine Burner

Large eddy simulations (LES) and experiments (planar laser-induced fluorescence of the hydroxyl radical (OH-PLIF) and pressure transducer) have been carried out on a gas turbine burner fitted to an atmospheric combustion rig. This burner, from the Siemens SGT-800 gas turbine, is a low NOx, partially premixed burner, where preheat air temperature, flame temperature, and pressure drop across the burner are kept similar to engine full load conditions. The large eddy simulations are based on a flamelet-generated manifold (FGM) approach for representing the chemistry and the Smagorinsky model for subgrid turbulence. The experimental data and simulation data are in good agreement, both in terms of time averaged and time-resolved quantities. From the experiments and LES, three bands of frequencies of pressure fluctuations with high power spectral density are found in the combustion chamber. The first two bands are found to be axial pressure modes, triggered by coherent flow motions from the burner, such as the flame stabilization location and the precessing vortex core (PVC). The third band is found to be a cross flow directional mode interacting with two of the four combustion chamber walls in the square section of the combustion chamber, triggered from general flow motions. This study shows that LES of real gas turbine components is feasible and that the results give important insight into the flow, flame, and acoustic interactions in a specific combustion system.

Pilot-Pilot Interaction Effects on a Prototype DLE Gas Turbine Burner Combustion

2016 ◽  
Author(s):  
Atanu Kundu ◽  
Jens Klingmann ◽  
Arman Ahamed Subash ◽  
Robert Collin
Keyword(s):  
Gas Turbine ◽  
Residence Time ◽  
Interaction Effect ◽  
Flame Stabilization ◽  
Experimental Results ◽  
Optical Measurements ◽  
Pollutant Emissions ◽  
Total Power ◽  
Low Emission ◽  
Pilot Fuel

Lean premixed dry low emission (DLE) combustion system in a gas turbine engine is a globally accepted concept to reduce pollutant emissions and to improve combustion efficiency. This study is focused on an industrial downscaled prototype burner (4th Generation Dry Low Emission Burner for SGT-750 designed and manufactured by Siemens Industrial Turbo machinery AB), which has been tested extensively at atmospheric conditions. To enhance the operability and alleviate flame dynamics behavior, multiple fuel and air circuits (i.e. Rich-Pilot-Lean (RPL), Pilot and Main) are engaged in the burner. Primarily, present study evaluates the RPL-Pilot interaction effect on the main combustion zone. A highly swirled flow from the burner exit produces a central recirculation zones (CRZ) to recirculate the hot vitiated gas for sustaining the combustion process. The main flame is stabilized in the inner shear layer (ISL), which is found in the diverging section (named as Quarl). The total power of the burner was varied between 70–140 kW and the fuel used for the experiment was 99.5% pure methane. A short length quartz liner was used for the experiment and the residence time of the combustor is 9 ms. At the liner exit, emission sampling (CO, NOx) has been conducted using a water-cooled emission probe. Optical measurements were permitted, as the Quarl and combustor liner were optically accessible. Planar laser-induced fluorescence of OH molecule (OH-PLIF) and natural chemiluminescence measurements were conducted to visualize the flame characteristics and its response by changing the RPL and Pilot fuel splits. A comprehensive study was performed by varying the RPL residence time to investigate the main flame stabilization and pollutant formation of the burner. Higher RPL residence time exhibits NOx benefits but at the same time flame instability was increased. Pilot fuel percentage modification demonstrate negative impact on NOx formation due to the limited mixing of fuel and air. With the increase of Pilot fuel split, CO emission decreases, which is advantageous for increasing the LBO margin. The study has identified a number of critical situations where the flame was stabilized without any RPL and Pilot combustion. Apart from the experimental results, a simple reactor network model has been applied for predicting NOx emission. Different kinetic mechanisms were assessed and the prediction results are compared to experimental results. Heat loss from the combustor wall played a significant role on emission formation and was included in the reactor model. This study provides a good understanding of the new DLE industrial burner concept and the RPL-pilot interaction effect on the emission.

Experimental and Numerical Study on Optimizing the Dry Low NOx Micromix Hydrogen Combustion Principle for Industrial Gas Turbine Applications

2016 ◽  
Vol 9 (2) ◽  
Author(s):  
Harald H. W. Funke ◽  
Jan Keinz ◽  
Karsten Kusterer ◽  
Anis Haj Ayed ◽  
Masahide Kazari ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Numerical Study ◽  
Renewable Energy Sources ◽  
Thermal Power ◽  
Flame Structure ◽  
High Energy ◽  
Hydrogen Combustion ◽  
Nox Emissions ◽  
Fuel Injectors ◽  
The Impact

Combined with the use of renewable energy sources for its production, hydrogen represents a possible alternative gas turbine fuel for future low-emission power generation. Due to the difference in the physical properties of hydrogen compared to other fuels such as natural gas, well-established gas turbine combustion systems cannot be directly applied to dry low NOx (DLN) hydrogen combustion. The DLN micromix combustion of hydrogen has been under development for many years, since it has the promise to significantly reduce NOx emissions. This combustion principle for air-breathing engines is based on crossflow mixing of air and gaseous hydrogen. Air and hydrogen react in multiple miniaturized diffusion-type flames with an inherent safety against flashback and with low NOx emissions due to a very short residence time of the reactants in the flame region. The paper presents an advanced DLN micromix hydrogen application. The experimental and numerical study shows a combustor configuration with a significantly reduced number of enlarged fuel injectors with high-thermal power output at constant energy density. Larger fuel injectors reduce manufacturing costs, are more robust and less sensitive to fuel contamination and blockage in industrial environments. The experimental and numerical results confirm the successful application of high-energy injectors, while the DLN micromix characteristics of the design point, under part-load conditions, and under off-design operation are maintained. Atmospheric test rig data on NOx emissions, optical flame-structure, and combustor material temperatures are compared to numerical simulations and show good agreement. The impact of the applied scaling and design laws on the miniaturized micromix flamelets is particularly investigated numerically for the resulting flow field, the flame-structure, and NOx formation.

Combustion Characteristics and Hydrogen Addition Effects on the Performance of a Can Combustor for a Micro Gas Turbine

2010 ◽  
Author(s):  
Hsin-Yi Shih ◽  
Chi-Rong Liu
Keyword(s):  
High Temperature ◽  
Gas Turbine ◽  
Temperature Region ◽  
Fuel Injection ◽  
Flame Temperature ◽  
Combustion Characteristics ◽  
High Temperature Region ◽  
Micro Gas Turbine ◽  
Blended Fuel ◽  
Co Emission

To better understand the combustion performance by using hydrogen/methane blended fuels for an innovative micro gas turbine which is designed originally as a natural gas fired engine, the combustion characteristics of a can type combustor has been modeled and the effects of hydrogen amount were investigated. The simulations were performed using the commercial code STAR-CD, in which the three-dimension compressible k-ε turbulent flow mode and presumed probability density function for chemical reaction between methane/hydrogen/air mixtures were used. The results showed the detailed flame structures including the flow fields, distributions of flame temperature, major species and gas emissions. A variable volumetric fraction of hydrogen from 0% to 80% and the fuel injection velocities of this blended fuel ranging from 20 m/s to 60 m/s were studied. When hydrogen amount is higher, the flame temperature and exit gas temperature increase; high temperature region becomes wider and shifts to the intermediate zone. As fuel inlet velocity decreases from 60 m/s to 20 m/s, the high temperature region shifts to the side of the combustor due to the high diffusivity of hydrogen. Compared to the combustion using pure methane, NOx emissions increase with blended fuel, but the increase of hydrogen amount does not produce any significant effect over emission level of NOx. However, CO emission reduction is more remarkable at low hydrogen fraction, but the level of CO emission increases drastically when the fuel injection velocity is lower. Further modifications of the combustor designs including the fuel injection and cooling strategies are needed to improve the combustion performance for the micro gas turbine engine with hydrogen blended fuel as an alternative.

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