Optimization of the Aerodynamic Flame Stabilization for Fuel Flexible Gas Turbine Premix Burners

2011 ◽  
Vol 133 (10) ◽  
Author(s):  
Stephan Burmberger ◽  
Thomas Sattelmayer
Keyword(s):  
Gas Turbine ◽  
Recirculation Zone ◽  
Vortex Breakdown ◽  
Flame Stabilization ◽  
Swirling Flows ◽  
Cross Sectional ◽  
Flame Chemistry ◽  
Flame Flashback ◽  
Sudden Transition ◽  
Vorticity Transport

A frequently employed method for aerodynamic flame stabilization in modern premixed low emission combustors is the breakdown of swirling flows; with carefully optimized tailoring of the swirler, a sudden transition in the flow field in the combustor can be achieved. A central recirculation zone evolves at the cross-sectional area change located at the entrance of the combustion chamber and anchors the flame in a fixed position. In general, premixed combustion in swirling flows can lead to flame flashback that is caused by combustion induced vortex breakdown near the centerline of the flow. In this case, the recirculation zone suddenly moves upstream and stabilizes in the premix zone (Kröner , 2007, “Flame Propagation in Swirling Flows—Effect of Local Extinction on the Combustion Induced Vortex Breakdown,” Combust. Sci. Technol., 179, pp. 1385–1416). This type of flame flashback is caused by a strong interaction between the flame chemistry and vortex dynamics. The analysis of the vorticity transport equation shows that the axial gradient of the azimuthal vorticity is of particular importance for flame stability. A negative azimuthal vorticity gradient decelerates the core flow and finally causes vortex breakdown. Based on fundamental fluid mechanics, guidelines for a proper aerodynamic design of gas turbine combustors are given. These guidelines summarize the experience from several previous aerodynamic and combustion studies of the authors.

Investigation of Flame Stabilization in a High-Pressure Multi-Jet Combustor by Laser Measurement Techniques

2014 ◽  
Author(s):  
Oliver Lammel ◽  
Tim Rödiger ◽  
Michael Stöhr ◽  
Holger Ax ◽  
Peter Kutne ◽  
...  
Keyword(s):  
High Pressure ◽  
Natural Gas ◽  
Combustion Chamber ◽  
Gas Turbine ◽  
Recirculation Zone ◽  
Flame Stabilization ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Single Shot ◽  
Optical Access

In this contribution, comprehensive optical and laser based measurements in a generic multi-jet combustor at gas turbine relevant conditions are presented. The flame position and shape, flow field, temperatures and species concentrations of turbulent premixed natural gas and hydrogen flames were investigated in a high-pressure test rig with optical access. The needs of modern highly efficient gas turbine combustion systems, i.e., fuel flexibility, load flexibility with increased part load capability, and high turbine inlet temperatures, have to be addressed by novel or improved burner concepts. One promising design is the enhanced FLOX® burner, which can achieve low pollutant emissions in a very wide range of operating conditions. In principle, this kind of gas turbine combustor consists of several nozzles without swirl, which discharge axial high momentum jets through orifices arranged on a circle. The geometry provides a pronounced inner recirculation zone in the combustion chamber. Flame stabilization takes place in a shear layer around the jet flow, where fresh gas is mixed with hot exhaust gas. Flashback resistance is obtained through the absence of low velocity zones, which favors this concept for multi-fuel applications, e.g. fuels with medium to high hydrogen content. The understanding of flame stabilization mechanisms of jet flames for different fuels is the key to identify and control the main parameters in the design process of combustors based on an enhanced FLOX® burner concept. Both experimental analysis and numerical simulations can contribute and complement each other in this task. They need a detailed and relevant data base, with well-known boundary conditions. For this purpose, a high-pressure burner assembly was designed with a generic 3-nozzle combustor in a rectangular combustion chamber with optical access. The nozzles are linearly arranged in z direction to allow for jet-jet interaction of the middle jet. This line is off-centered in y direction to develop a distinct recirculation zone. This arrangement approximates a sector of a full FLOX® gas turbine burner. The experiments were conducted at a pressure of 8 bar with preheated and premixed natural gas/air and hydrogen/air flows and jet velocities of 120 m/s. For the visualization of the flame, OH* chemiluminescence imaging was performed. 1D laser Raman scattering was applied and evaluated on an average and single shot basis in order to simultaneously and quantitatively determine the major species concentrations, the mixture fraction and the temperature. Flow velocities were measured using particle image velocimetry at different section planes through the combustion chamber.

Dynamic Adaptation of Aerodynamic Flame Stabilization of a Premix Swirl Burner to Fuel Reactivity Using Fuel Momentum

2010 ◽  
Author(s):  
J. Sangl ◽  
C. Mayer ◽  
T. Sattelmayer
Keyword(s):  
Gas Turbine ◽  
Vortex Dynamics ◽  
Vortex Breakdown ◽  
Water Channel ◽  
Chemical Properties ◽  
Flame Stabilization ◽  
Fuel Gas ◽  
Volumetric Heating ◽  
Main Challenge ◽  
Reactive Gases

Due to the expected increase in available fuel gas variants in the future and the interest in independence from a specific fuel, fuel flexible combustion systems are required for future gas turbine applications. Changing the fuel used for lean premixed combustion can lead to serious reliability problems in gas turbine engines caused by the different physical and chemical properties of these gases. A new innovative approach to reach efficient, safe and low-emissions operation for fuels like natural gas, syntheses gas and hydrogen with the same burner is presented in this paper. The basic idea is to use the additionally available fuel momentum of highly reactive gases stemming from their lower Wobbe index (lower volumetric heating value and density) compared to lowly reactive fuels. Using fuel momentum opens the opportunity to influence the vortex dynamics of swirl burners designed for lowly reactive gases in a favorable way for proper flame stabilization of highly reactive fuels without changing the hardware geometry. The investigations presented in the paper cover the development of the optimum basic aerodynamics of the burner and the determination of the potential of the fuel momentum in water channel experiments using particle image velocimetry (PIV). The results show that a proper usage of the fuel momentum has enough potential to adjust the flow field to the different fuels and their corresponding flame behavior. As the main challenge is to reach flashback safe fuel flexible burner operation, the main focus of the study lies on avoiding combustion induced vortex breakdown (CIVB). The mixing quality of the resulting injection strategy is determined applying laser induced fluorescence (LIF) in water channel tests. Additional OH* chemiluminescence and flashback measurements in an atmospheric combustion test rig confirm the water channel results for CH4, CH4/H2 mixtures, H2 with N2 dilution and pure H2 combustion. They also indicate a large operating window between flashback and lean blow out and show expected NOx emission levels. In summary, it is shown for a conical four slot swirl generator geometry that the proposed concept of using the fuel momentum for tuning of the vortex dynamics allows aerodynamic flame stabilization for different fuels in the same burner.

Dynamic Adaptation of Aerodynamic Flame Stabilization of a Premix Swirl Burner to Fuel Reactivity Using Fuel Momentum

2011 ◽  
Vol 133 (7) ◽  
Author(s):  
J. Sangl ◽  
C. Mayer ◽  
T. Sattelmayer
Keyword(s):  
Gas Turbine ◽  
Vortex Dynamics ◽  
Vortex Breakdown ◽  
Water Channel ◽  
Chemical Properties ◽  
Flame Stabilization ◽  
Fuel Gas ◽  
Volumetric Heating ◽  
Main Challenge ◽  
Reactive Gases

Due to the expected increase in available fuel gas variants in the future and the interest in independence from a specific fuel, fuel flexible combustion systems are required for future gas turbine applications. Changing the fuel used for lean premixed combustion can lead to serious reliability problems in gas turbine engines caused by the different physical and chemical properties of these gases. A new innovative approach to reach efficient, safe, and low-emission operation for fuels such as natural gas, syntheses gas, and hydrogen with the same burner is presented in this paper. The basic idea is to use the additionally available fuel momentum of highly reactive gases stemming from their lower Wobbe index (lower volumetric heating value and density) compared with lowly reactive fuels. Using fuel momentum opens the opportunity to influence the vortex dynamics of swirl burners designed for lowly reactive gases in a favorable way for proper flame stabilization of highly reactive fuels without changing the hardware geometry. The investigations presented in this paper cover the development of the optimum basic aerodynamics of the burner and the determination of the potential of the fuel momentum in water channel experiments using particle image velocimetry. The results show that proper usage of the fuel momentum has enough potential to adjust the flow field to different fuels and their corresponding flame behavior. As the main challenge is to reach flashback safe fuel flexible burner operation, the main focus of the study lies on avoiding combustion induced vortex breakdown. The mixing quality of the resulting injection strategy is determined by applying laser induced fluorescence in water channel tests. Additional OH∗ chemiluminescence and flashback measurements in an atmospheric combustion test rig confirm the water channel results for CH4, CH4/H2 mixtures, H2 with N2 dilution, and pure H2 combustion. They also indicate a large operating window between flashback and lean blow out and show expected NOx emission levels. In summary, it is shown for a conical four slot swirl generator geometry that the proposed concept of using the fuel momentum for tuning of the vortex dynamics allows aerodynamic flame stabilization for different fuels in the same burner.

Combustion Control by Vortex Breakdown Stabilization

2002 ◽  
Vol 128 (4) ◽  
pp. 679-688 ◽  
Author(s):  
Christian Oliver Paschereit ◽  
Peter Flohr ◽  
Ephraim J. Gutmark
Keyword(s):  
Gas Turbine ◽  
Recirculation Zone ◽  
Fuel Injection ◽  
Vortex Breakdown ◽  
Full Scale ◽  
Operating Conditions ◽  
Scale Model ◽  
Recirculation Region ◽  
Pressure Pulsations ◽  
Secondary Fuel

Flame anchoring in a swirl-stabilized combustor occurs in an aerodynamically generated recirculation region which is a result of vortex breakdown (VBD). The characteristics of the recirculating flow are dependent on the swirl number and on axial pressure gradients. Coupling with downstream pressure pulsations in the combustor affects the VBD process. The present paper describes combustion instability that is associated with vortex breakdown. The mechanism of the onset of this instability is discussed. Passive control of the instability was achieved by stabilizing the location of vortex breakdown using an extended lance. The reduction of pressure pulsations for different operating conditions and the effect on emissions in a laboratory scale model atmospheric combustor, in a high pressure combustor facility, and in a full scale land-based gas-turbine are described. The flashback safety, one of the most important features of a reliable gas turbine burner, was assessed by CFD, water tests, and combustion tests. In addition to the passive stabilization by the extended lance it enabled injection of secondary fuel directly into the recirculation zone where the flame is stabilized. Tests were conducted with and without secondary fuel injection. Measurements and computations optimized the location of the extended lance in the mixing chamber. The effect of variation of the amount of secondary fuel injection at different equivalence ratios and output powers was determined. Flow visualizations showed that stabilization of the recirculation zone was achieved. Following the present research, the VBD stabilization method has been successfully implemented in engines with sufficient stability margins and good operational flexibility. This paper shows the development process from lab scale tests to full scale engine tests until the implementation into field engines.

Combustion Control by Extended EV Burner Fuel Lance

2002 ◽  
Author(s):  
Christian Oliver Paschereit ◽  
Peter Flohr ◽  
Hanspeter Kno¨pfel ◽  
Weiqun Geng ◽  
Christian Steinbach ◽  
...  
Keyword(s):  
Recirculation Zone ◽  
Fuel Injection ◽  
Vortex Breakdown ◽  
Flame Stabilization ◽  
Full Scale ◽  
Recirculation Region ◽  
Operational Flexibility ◽  
Stability Margins ◽  
Recirculating Flow ◽  
Secondary Fuel

Flame stabilization in a swirl-stabilized combustor occurs in an aerodynamically generated recirculation region which is a result of vortex breakdown. The characteristics of the recirculating flow are dependent on the swirl number and on axial pressure gradients. Coupling to downstream pressure pulsations is also possible. In order to fix the position of the recirculation zone, an extended fuel lance was inserted into the burner. An additional benefit of the extended lance was to enable secondary fuel injection directly into the recirculation zone where the flame is stabilized. Tests were conducted with and without secondary fuel injection. The measurements included optimization of the location of the extended lance in the mixing chamber and variation of the amount of secondary fuel injection at different equivalence ratios and output powers. Flow visualizations showed that stabilization of the recirculation zone was achieved. The effect of the extended lance on pressure and heat release oscillations and on emissions of NOx, UHC and CO was investigated. The results were confirmed in high pressure single burner pressure tests and in a full scale land-based test gas-turbine. The lance has been successfully implemented in engines with sufficient stability margins and good operational flexibility. This paper shows the careful development process from lab scale tests to full scale engine tests until the implementation into the field engines.

Development of a Jet-Stabilized Low-Emission Combustor for Liquid Fuels

2015 ◽  
Author(s):  
Anton Zizin ◽  
Oliver Lammel ◽  
Michael Severin ◽  
Holger Ax ◽  
Manfred Aigner
Keyword(s):  
Gas Turbine ◽  
Recirculation Zone ◽  
Soot Formation ◽  
Flame Stabilization ◽  
Liquid Fuels ◽  
Cfd Modeling ◽  
Design Parameters ◽  
Spray Cone ◽  
Low Emission ◽  
Flame Shape

In this work the ongoing development of a jet-stabilized FLOX®(Flameless Oxidation)-type low-emission combustor for liquid fuels is described. The desired application of this concept is a micro gas turbine range extender for next generation car concepts. Diesel DIN EN 590 was used to operate the combustor, which is very similar to other fuels like bio-diesel, light heating oil and kerosene and therefore provides a link to other gas turbine applications in power generation. The investigation of flame stabilization of jet flames as well as fuel atomization, spray dispersion and evaporation is essential for the design of an effective and reliable combustor for liquid fuels. An axisymmetric single-nozzle combustion chamber was chosen for the initial setup. A variety of burner configurations was tested in order to investigate the influence of different design parameters on the flame shape, the flame stability and emissions. Two pressure atomizers and one air-blast atomizer were combined with two types of air nozzles and two different burner front plates (axisymmetric and off-centered jet nozzle). Finally, a twelve nozzle FLOX® combustor with pre-evaporator was designed and characterized. The combustor was operated at atmospheric pressure with preheated air (300° C) and in a range of equivalence ratios φ between 0.5 and 0.95 (λ = 1.05–2). The maximum thermal power was 40 kW. For each combustor configuration and operating condition the flame shape was imaged by OH*-chemiluminescence, together with an analysis of the exhaust gas emissions. Laser sheet imaging was used to identify the spray geometry for all axisymmetric combustors. Wall temperatures were measured for two configurations using temperature sensitive paints, which will be utilized in future CFD modeling. The results show a dependence of NOx emissions on the flame’s lift-off height, which in turn is defined by the spray properties and evaporation conditions. The tendency to soot formation was strongly dependent on the correlation of the recirculation zone to the spray cone geometry. In particular, strong soot formation was observed when unevaporated droplets entered the recirculation zone.

Designing a Radial Swirler Vortex Breakdown Burner

2006 ◽  
Author(s):  
Stephan Burmberger ◽  
Christoph Hirsch ◽  
Thomas Sattelmayer
Keyword(s):  
Flow Field ◽  
Vortex Breakdown ◽  
Swirling Flow ◽  
Azimuthal Velocity ◽  
Design Guidelines ◽  
Flame Stabilization ◽  
Fuel Flexibility ◽  
Primary Zone ◽  
Large Eddy ◽  
Flame Flashback

Most gas turbine premix burners without centrebody employ the breakdown of a swirling flow at the transition between the mixing section and the combustor for aerodynamic flame stabilization [1]. As the formation of the desired vortex breakdown pattern depends very sensibly on the distribution of axial and azimuthal velocity in the mixing section, the design of suitable swirlers is usually a cumbersome iterative process. The presented burner design was found through the implementation of design guidelines derived from CFD-calculations and on the basis of analytical considerations [5]. The swirling flow is generated by a radial swirler with tangential inlets. In order to stabilize the flow pattern, the swirling flow confines a slow non-swirling flow on the centreline. The centre flow being set into azimuthal motion creates increasing azimuthal velocity in streamwise direction in the vortex core. This process is reinforced by a conical nozzle and leads to the production of positive azimuthal vorticity inside the nozzle which stabilizes the flow field. First atmospheric test runs and Large Eddy Simulations of the isothermal as well as reactive flow field prove that the design goals have been reached: The burner creates stable vortex breakdown in the primary zone of the combustion chamber without flame flashback or backflow on the centreline over the entire operating range and even for difficult fuels like hydrogen containing gases. This finding indicates that reliable vortex breakdown burners with remarkable fuel flexibility can be designed using the guidelines presented in [5].

Unsteady Flow Structures in Radial Swirler Fed Fuel Injectors

2004 ◽  
Vol 127 (4) ◽  
pp. 755-764 ◽  
Author(s):  
Kris Midgley ◽  
Adrian Spencer ◽  
James J. McGuirk
Keyword(s):  
Unsteady Flow ◽  
Recirculation Zone ◽  
Vortex Breakdown ◽  
Vortex Structures ◽  
Flame Stabilization ◽  
Flow Structures ◽  
Time Averaging ◽  
Fuel Injector ◽  
Specific Flow ◽  
Unsteady Aerodynamic

Many fuel injector geometries proposed for lean-premixed combustion systems involve the use of radial swirlers. At the high swirl numbers needed for flame stabilization, several complex unsteady fluid mechanical phenomena such as vortex breakdown and recirculation zone precession are possible. If these unsteady aerodynamic features are strongly periodic, unwanted combustion induced oscillation may result. The present paper reports on an isothermal experimental study of a radial swirler fed fuel injector originally designed by Turbomeca, and examines the dynamical behavior of the unsteady aerodynamic flow structures observed. Particle Image Velocimetry (PIV) is used to capture the instantaneous appearance of vortex structures both internal to the fuel injector, and externally in the main flame-stabilizing recirculation zone. Multiple vortex structures are observed. Vector field analysis is used to identify specific flow structures and perform both standard and conditional time averaging to reveal the modal characteristics of the structures. This allows analysis of the origin of high turbulence regions in the flow and links between internal fuel injector vortex breakdown and external unsteady flow behavior. The data provide a challenging test case for Large Eddy Simulation methods being developed for combustion system simulation.

scholarly journals Development of Micro Gas Turbine Combustor with a Recirculation Zone Induced by an Upward Swirl

2008 ◽  
Vol 3 (1) ◽  
pp. 204-215
Author(s):  
Kousaku YOTORIYAMA ◽  
Shunsuke AMANO ◽  
Hidetomo FUJIWARA ◽  
Tomohiko FURUHATA ◽  
Masataka ARAI
Keyword(s):  
Gas Turbine ◽  
Recirculation Zone ◽  
Gas Turbine Combustor ◽  
Micro Gas Turbine

The Civic: A Concept in Vortex Induced Combustion for the Solar Gemini 10 kW Gas Turbine

1981 ◽  
Vol 103 (1) ◽  
pp. 34-42 ◽  
Author(s):  
J. R. Shekleton
Keyword(s):  
Gas Turbine ◽  
Diffusion Flames ◽  
Reynolds Numbers ◽  
Flame Stabilization ◽  
Fuel Injector ◽  
Combustion Chambers ◽  
Turbine Generator ◽  
Fuel Injectors ◽  
Swirl Flame ◽  
Combustion Processes

The Radial Engine Division of Solar Turbines International, an Operating Group of International Harvester, under contract to the U.S. Army Mobility Equipment Research & Development Command, developed and qualified a 10 kW gas turbine generator set. The very small size of the gas turbine created problems and, in the combustor, novel solutions were necessary. Differing types of fuel injectors, combustion chambers, and flame stabilizing methods were investigated. The arrangement chosen had a rotating cup fuel injector, in a can combustor, with conventional swirl flame stabilization but was devoid of the usual jet stirred recirculation. The use of centrifugal force to control combustion conferred substantial benefit (Rayleigh Instability Criteria). Three types of combustion processes were identified: stratified and unstratified charge (diffusion flames) and pre-mix. Emphasis is placed on five nondimensional groups (Richardson, Bagnold, Damko¨hler, Mach, and Reynolds numbers) for the better control of these combustion processes.

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