Academic literature on the topic 'Sequential auto-ignition'
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Journal articles on the topic "Sequential auto-ignition"
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Xiong, Yuan, Oliver Schulz, Claire Bourquard, Markus Weilenmann, and Nicolas Noiray. "Plasma enhanced auto-ignition in a sequential combustor." Proceedings of the Combustion Institute 37, no. 4 (2019): 5587–94. http://dx.doi.org/10.1016/j.proci.2018.08.031.
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Liu, Erwei, Qin Liao, and Shengli Xu. "Aerosol Shock Tube Designed for Ignition Delay Time Measurements of Low-Vapor-Pressure Fuels and Auto-Ignition Flow-Field Visualization." Energies 13, no. 3 (February 5, 2020): 683. http://dx.doi.org/10.3390/en13030683.
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An aerosol shock tube has been developed for measuring the ignition delay times (tig) of aerosol mixtures of low-vapor-pressure fuels and for visualization of the auto-ignition flow-field. The aerosol mixture was formed in a premixing tank through an atomizing nozzle. Condensation and adsorption of suspended droplets were not observed significantly in the premixing tank and test section. A particle size analyzer was used to measure the Sauter mean diameter (SMD) of the aerosol droplets. Three pressure sensors and a photomultiplier were used to detect local pressure and OH emission respectively. Intensified charge-coupled device cameras were used to capture sequential images of the auto-ignition flow-field. The results indicated that stable and uniform aerosol could be obtained by this kind of atomizing method and gas distribution system. The averaged SMD for droplets of toluene ranged from 2 to 5 μ m at pressures of 0.14–0.19 MPa of dilute gases. In the case of a stoichiometric mixture of toluene/O2/N2, ignition delay times ranged from 77 to 1330 μs at pressures of 0.1–0.3 MPa, temperatures of 1432–1716 K and equivalence ratios of 0.5–1.5. The logarithm of ignition delay times was approximately linearly correlated to 1000/T. In contrast to the reference data, ignition delay times of aerosol toluene/O2/N2 were generally larger. Sequential images of auto-ignition flow-field showed the features of flame from generation to propagation.
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Wolk, Benjamin, Jyh-Yuan Chen, and John E. Dec. "Computational study of the pressure dependence of sequential auto-ignition for partial fuel stratification with gasoline." Proceedings of the Combustion Institute 35, no. 3 (2015): 2993–3000. http://dx.doi.org/10.1016/j.proci.2014.05.023.
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Yang, Can, Haocheng Xu, Tengyuan Long, and Xiaobei Cheng. "On improving the controllability of low-temperature combustion by building two-stage sequential high-temperature reactions in an ethanol/diesel dual-fuel engine using multiple injections." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, April 9, 2021, 095765092199688. http://dx.doi.org/10.1177/0957650921996887.
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Low-temperature combustion (LTC) has advantages in reducing emissions and improving efficiency, at the expense of hard controllability. To improve its controllability, this paper proposes a two-stage stratified compression ignition (TSCI) strategy, which aims to decouple ignition and the following combustion as two-stage sequential high-temperature reactions, and couple them to external events like multiple injections, supercharge, etc. A trace amount of high reactivity fuel (HRF) is injected near the top dead center (TDC) and auto-ignited, initiating the combustion process, which controls ignition. The highly premixed charge (HPC), whose equivalent ratio, temperature, reactivity can be tuned as needed, control the combustion course after ignition. Based on the TSCI concept, one demonstrative multiple-injection strategy is suggested and tested on a single-cylinder ethanol/diesel dual-fuel engine. It is concluded from the experimental results that the TSCI combustion process presents two-stage sequential high-temperature reactions, which is different from any other LTC strategies. This sequential combustion shows good controllability. Within a certain range, the ignition phase is directly and linearly related to the ignition-oriented injection (IOI) event. With the advance of IOI timing, the ignition is advanced consequently. Increasing IOI quantity has the same tendency. As for HPC, when HPC reactivity is increased, the maximum pressure raising rate (MPRR) is increased and the whole combustion process is more concentrated.
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Bothien, Mirko, Demian Lauper, Yang Yang, and Alessandro Scarpato. "Reconstruction and Analysis of the Acoustic Transfer Matrix of a Reheat Flame From Large-Eddy Simulations." Journal of Engineering for Gas Turbines and Power 141, no. 2 (October 4, 2018). http://dx.doi.org/10.1115/1.4041151.
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Lean premix technology is widely spread in gas turbine combustion systems, allowing modern power plants to fulfill very stringent emission targets. These systems are, however, also prone to thermoacoustic instabilities, which can limit the engine operating window. The thermoacoustic analysis of a combustor is thus a key element in its development process. An important ingredient of this analysis is the characterization of the flame response to acoustic fluctuations, which is straightforward for lean-premixed flames that are propagation stabilized, since it can be measured atmospherically. Ansaldo Energia's GT26 and GT36 reheat combustion systems feature a unique technology where fuel is injected into a hot gas stream from a first combustor, which is propagation stabilized, and auto-ignites in a sequential combustion chamber. The present study deals with the flame response of mainly auto-ignition stabilized flames to acoustic and temperature fluctuations for which a computational fluid dynamics system identification (SI) approach is chosen. The current paper builds on recent works, which detail and validate a methodology to analyze the dynamic response of an auto-ignition flame to extract the flame transfer function (FTF) using unsteady large-Eddy simulations (LES). In these studies, the flame is assumed to behave as a single-input single-output (SISO) or a multi-input single-output (MISO) system. The analysis conducted in GT2015-42622 qualitatively highlights the important role of temperature and equivalence ratio fluctuations, but these effects are not separated from velocity fluctuations. Hence, this topic is addressed in GT2016-57699, where the flame is treated as a multiparameter system and compressible LES are conducted to extract the frequency-dependent FTF to describe the effects of axial velocity, temperature, equivalence ratio, and pressure fluctuations on the flame response. For lean-premixed flames, a common approach followed in the literature assumes that the acoustic pressure is constant across the flame and that the flame dynamics are governed by the response to velocity perturbations only, i.e., the FTF. However, this is not necessarily the case for reheat flames that are mainly auto-ignition stabilized. Therefore, in this paper, we present the full 2 × 2 transfer matrix of a predominantly auto-ignition stabilized flame, and hence, describe the flame as a multi-input multi-output (MIMO) system. In addition to this, it is highlighted that in the presence of temperature fluctuations, the 2 × 2 matrix can be extended to a 3 × 3 matrix relating the primitive acoustic variables as well as the temperature fluctuations across the flame. It is shown that only taking the FTF is insufficient to fully describe the dynamic behavior of reheat flames.
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Levy, Yeshayahou, Vladimir Erenburg, Valery Sherbaum, and Igor Gaissinski. "Development of Combustor for a Hybrid Turbofan Engine." International Journal of Turbo & Jet-Engines, December 4, 2019. http://dx.doi.org/10.1515/tjj-2019-0042.
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Abstract A promising method of reducing NOx emissions in combustion systems is the Flameless oxidation (FO), which is based on significant dilution of the oxygen concentration in the reactant stream and elevating its temperature to above auto ignition level. The present work is aimed at developing an FO based combustor for a sequential combustion turbofan engine, where the primary combustor is fuelled with H2 and the secondary combustor with hydrocarbon (jet or bio-jet) fuel. The work was performed within the framework of the European project AHEAD (www.ahead-euproject.eu). Being situated between the high pressure and the low pressure turbines, the inlet conditions to the FO combustor are non-conventional. CHEMKIN simulations revealed the theoretical feasibility of a combustion system to operate in the FO mode of combustion under the specific Take-off and Cruise operating conditions. Several design iterations were conducted to find an appropriate geometrical configuration that would allow for such a system to operate in a stable manner. The design iterations were followed by CFD simulations (FLUENT) and a final design was an achieved where the predictions indicated nearly uniform internal temperature distribution with low mass fraction of CO and NOx at the exhaust.
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Guyot, Daniel, Gabrielle Tea, and Christoph Appel. "Low NOx Lean Premix Reheat Combustion in Alstom GT24 Gas Turbines." Journal of Engineering for Gas Turbines and Power 138, no. 5 (October 27, 2015). http://dx.doi.org/10.1115/1.4031543.
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Reducing gas turbine emissions and increasing their operational flexibility are key targets in today's gas turbine market. In order to further reduce emissions and increase the operational flexibility of its GT24 (60 Hz) and GT26 (50 Hz), Alstom has introduced an improved sequential environmental (SEV) burner and fuel lance into its GT24 and GT26 upgrades 2011 sequential reheat combustion system. Sequential combustion is a key differentiator of Alstom GT24/GT26 engines in the F-class gas turbine market. The inlet temperature for the SEV combustor is around 1000 °C and reaction of the fuel/oxidant mixture is initiated through auto-ignition. The recent development of the Alstom sequential combustion system is a perfect example of evolutionary design optimizations and technology transfer between Alstom GT24 and GT26 engines. Better overall performance is achieved through improved SEV burner aerodynamics and fuel injection, while keeping the main features of the sequential burner technology. The improved SEV burner/lance concept has been optimized toward rapid fuel/oxidant mixing for low emissions, improved fuel flexibility with regard to highly reactive fuels (higher C2+ and hydrogen content), and to sustain a wide operation window. The burner front panel features an improved cooling concept based on near-wall cooling as well as integrated acoustics damping devices designed to reduce combustion pulsations, thus extending the SEV combustor's operation window even further. After having been validated extensively in Alstom's high pressure (HP) sector rig test facility, the improved GT24 SEV burner has been retrofitted into a commercial GT24 field engine for full engine validation during long-term operation. This paper presents the obtained HP sector rig and engine validation results for the GT24 (2011) SEV burner/lance hardware with a focus on reduced NOx and CO emissions and improved operational behavior of the SEV combustor. The HP tests demonstrated robust SEV burner/lance operation with up to 50% lower NOx formation and a more than 70 K higher SEV burner inlet temperature compared to the GT24 (2006) hardware. For the GT24 engine with retrofitted upgrade 2011 SEV burner/lance, all validation targets were achieved including an extremely robust operation behavior, up to 40% lower GT NOx emissions, significantly lower CO emissions at partload and baseload, a very broad operation window (up to 100 K width in SEV combustor inlet temperature), and all measured SEV burner/lance temperatures in the expected range. Sector rig and engine validation results have confirmed the expected SEV burner fuel flexibility (up to 18 vol. % C2+ and up to 5 vol. % hydrogen as standard).
Dissertations / Theses on the topic "Sequential auto-ignition"
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mubarak, ali mohammed jaasim. "Modeling of Pre-ignition and Super-knock in Spark Ignition Engines." Diss., 2018. http://hdl.handle.net/10754/628315.
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Advanced combustion concepts are required to meet the increasing global energy demand and stringent emission regulations imposed by the governments on automobile manufacturers. Improvement in efficiency and reduction in emissions can be achieved by downsizing the Spark Ignition (SI) engines. The operating range of SI engine is limited by occurrence of knock, pre-ignition and the following super-knock due to boosting of intake pressure, to account for the reduction of power, as a result of downsizing the engine. Super-knock, which represents high momentary pressure accompanied with pressure oscillations, is known to permanently damage the moving component of the engines. Therefore fundamental comprehensive understanding of the mechanism involved in pre-ignition and super-knock are required to design highly efficient spark ignition engines with lower emissions that can meet the increasing government regulations.
\nThe thesis focuses on auto-ignition characteristics of endgas and the bulk mixture properties that favor transition of pre-ignition to super-knock. Direct numerical studies indicate that super-knock occurs to due to initiation of premature flame front that transition into detonation. In literature, many sources are reported to trigger pre-ignition. Due to the uncertainty of the information on the sources that trigger pre-ignition, it is extremely difficult to predict and control pre-ignition event in SI engines. Since the information on the source of pre-ignition is not available, the main focus of this work is to understand the physical and chemical mechanisms involved in super-knock, factors that influence super-knock and methods to predict super-knock.
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Pre-ignition was initiated at known locations and crank angle using a hotspot of known size and strength. Different parametric cases were studied and the location and timing of pre-ignition initiation is found to be extremely important in determining the transition of pre-ignition event to super-knock. Pre-ignition increases the temperature of the endgas and the overall bulk mixture, that transitions the pre-ignition flame front to a detonation. The transition of the flame propagation mode from deflagration to detonation was investigated with different type of analysis methods and all results confirmed the transition of pre-ignition flame front to detonation that results in super- knock.
Conference papers on the topic "Sequential auto-ignition"
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Kulkarni, Rohit, John P. Wood, Mario Zuber, and Hasan U. Karim. "Numerical Simulation of a Reacting Jet in a Vitiated Cross Flow Using a Novel Progress Variable Approach." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-64325.
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Staged/sequential combustion is a state of the art method to provide operational flexibility and reduced emissions in gas turbines. To use Computational Fluid Dynamics (CFD) to study such systems a reliable and computationally inexpensive turbulent combustion model is necessary. A key requisite for such a model is the accurate determination of the flame location in order to predict emissions, flame dynamics, and temperature distribution. Previously a model was developed for reheat combustion, based on a progress-variable method using auto-ignition reactors. However, sequential combustion systems are now being implemented where both auto-ignition and flame propagation are important. Consequently, the reheat model has been extended to consider flame propagation in mixtures that do not auto-ignite. This has been achieved by incorporating a small proportion of combustion products in the reactant mixture considered by the reactor. This approach has broadened the model’s applicability to address the full space between auto-ignition and flame propagation regimes. The revised model has been validated by comparison with reacting jet in vitiated cross-flow experiments demonstrating a significantly better prediction of the position of both attached and lifted flames than the original model.
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Tautschnig, G., E. M. Haner, C. Hirsch, and T. Sattelmayer. "Experimental and Numerical Investigation of Confined Jets in Hot Co-Flow." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-25843.
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Sequential staged combustion with an expansion turbine between both stages is an efficient way of extending the low emission regime of gas turbines towards very low loads. The dominating combustion regime in the second stage is auto-ignition. A confined natural gas jet in hot vitiated co-flow is investigated to obtain deeper insights in the parameters effecting auto-ignition. A generic pressurized combustion experiment is presented. Optical measurement techniques are applied to determine lift-off height and air excess ratio of the flame in the ignition region. Oxygen content of the co-flow, momentum flux ratio and pressure are varied in the experiments. Cold flow measurements are used to analyze the mixing behavior for different momentum flux ratios. Tendencies observed in the experiments are successfully simulated by a numerical method wherein the flow-, mixture- and temperature-fields are acquired using a non-reacting Realizable k-ε RANS simulation in Fluent. Mixture-PDFs obtained from water-channel measurements are used to take mixture-fluctuations into account. In a post-processing step the combustion-process is calculated with unsteady flamelet equations evaluated in Matlab. By using a progress variable approach with tabulated chemistry only two partial differential equations need to be solved. Hence the computational cost is low. With this study a low-cost numerical model for auto-ignition is demonstrated and the effect of temperature gradients in the co-flow on self-ignition is highlighted.
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Bothien, Mirko, Demian Lauper, Yang Yang, and Alessandro Scarpato. "Reconstruction and Analysis of the Acoustic Transfer Matrix of a Reheat Flame From Large-Eddy Simulations." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-64188.
Full textAbstract:
Lean premix technology is widely spread in gas turbine combustion systems, allowing modern power plants to fulfill very stringent emission targets. These systems are, however, also prone to thermoacoustic instabilities, which can limit the engine operating window. The thermoacoustic analysis of a combustor is thus a key element in its development process. An important ingredient of this analysis is the characterization of the flame response to acoustic fluctuations, which is straightforward for lean-premixed flames that are propagation stabilized, since it can be measured atmospherically. Ansaldo Energia’s GT26 and GT36 reheat combustion systems feature a unique technology where fuel is injected into a hot gas stream from a first combustor, which is propagation stabilized, and auto-ignites in a sequential combustion chamber. The present study deals with the flame response of mainly auto-ignition stabilized flames to acoustic and temperature fluctuations for which a CFD system identification approach is chosen. The current paper builds on recent works, which detail and validate a methodology to analyze the dynamic response of an auto-ignition flame to extract the Flame Transfer Function (FTF) using unsteady Large-Eddy Simulations (LES). In these studies, the flame is assumed to behave as a Single-Input Single-Output (SISO) or Multi-Input Single-Output (MISO) system. The analysis conducted in GT2015-42622 qualitatively highlights the important role of temperature and equivalence ratio fluctuations, but these effects are not separated from velocity fluctuations. Hence, this topic is addressed in GT2016-57699, where the flame is treated as a multi-parameter system and compressible LES are conducted to extract the frequency-dependent FTF to describe the effects of axial velocity, temperature, equivalence ratio and pressure fluctuations on the flame response. For lean-premixed flames, a common approach followed in the literature assumes that the acoustic pressure is constant across the flame and that the flame dynamics are governed by the response to velocity perturbations only, i.e., the FTF. However this is not necessarily the case for reheat flames that are mainly auto-ignition stabilized. Therefore, in this paper we present the full 2 × 2 transfer matrix of a predominantly auto-ignition stabilized flame and hence describe the flame as a Multi-Input Multi-Output (MIMO) system. In addition to this, it is highlighted that in presence of temperature fluctuations the 2 × 2 matrix can be extended to a 3 × 3 matrix relating the primitive acoustic variables as well as the temperature fluctuations across the flame. It is shown that only taking the FTF is insufficient to fully describe the dynamic behavior of reheat flames.
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Berger, Frederik M., Tobias Hummel, Pedro Romero Vega, Bruno Schuermans, and Thomas Sattelmayer. "A Novel Reheat Combustor Experiment for the Analysis of High-Frequency Flame Dynamics: Concept and Experimental Validation." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-77101.
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This paper presents a novel sequential combustor experiment for the study of reheat flame responses to high-frequency, transversal thermoacoustic oscillations. The reheat combustion chamber is of flat, quasi two-dimensional design to distinctly separate combustion areas dominated by auto-ignition and aerodynamic flame stabilization. This specific combustor setup furthermore promotes the occurrence of pressure pulsations at the first transverse resonance frequency, often referred to as screech. For investigation of combustion and acoustic properties, the reheat stage is equipped with pulsation probes at the face plate, and the entire combustion zone is optically accessible from all lateral sides to allow for (laser-) optical flame and flow diagnostics. In order to validate the qualification of the experimental setup for investigations of high-frequency flame dynamics, the reheat combustion regime and resulting transverse pressure dynamics are investigated. The desired flame shape with distinct auto-ignition and aerodynamic flame stabilization zones is achieved and can be sensibly controlled. Analyzing the frequency spectrum of the dynamic pressure measurements at the combustor face plate reveals the first transverse resonance at approximately 1600 Hz, which satisfies a key goal of the specific design. Overall, the setup qualifies for studying flame-acoustics interaction in reheat combustors and provides an experimental benchmark for modeling efforts and their validation. This will eventually contribute to design countermeasures to thermoacoustic pulsations for improved future generations of gas turbine combustors.
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Levy, Y., V. Erenburg, V. Sherbaum, and I. Gaissinski. "Flameless Oxidation Combustor Development for a Sequential Combustion Hybrid Turbofan Engine." In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-58079.
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A promising method of reducing NOx emissions in combustion systems is the Flameless oxidation (FO), which is based on significant dilution of the oxygen concentration in the reactant stream and elevating its temperature to above auto ignition level. The present work is aimed at developing an FO based combustor for a sequential combustion turbofan engine, where the primary combustor is fuelled with H2 and the secondary combustor with hydrocarbon (jet or bio-jet) fuel. The work was performed within the framework of the European project AHEAD (www.ahead-euproject.eu). Being situated between the high pressure and the low pressure turbines, the inlet conditions to the FO combustor are non-conventional. CHEMKIN simulations revealed the theoretical feasibility of a combustion system to operate in the FO mode of combustion under the specific Take off and Cruise operating conditions. Several design iterations were conducted to find an appropriate geometrical configuration that would allow for such a system to operate in a stable manner. The design iterations were followed by intensive CFD simulations (FLUENT) and a final design was a achieved where the predictions indicated nearly uniform internal temperature distribution with low mass fraction of CO (14.4ppm) and NOx (0.5 ppm) at the exhaust. A separate experimental verification study was performed and confirmed the ability of the CFD model to predict the behaviour of such a combustion configuration within the hybrid turbofan engine and its results will be published elsewhere.
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McClure, Jonathan, Frederik M. Berger, Michael Bertsch, Bruno Schuermans, and Thomas Sattelmayer. "Self-Excited High-Frequency Transverse Limit-Cycle Oscillations and Associated Flame Dynamics in a Gas Turbine Reheat Combustor Experiment." In ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/gt2021-59540.
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Abstract This paper presents the investigation of high-frequency thermoacoustic limit-cycle oscillations in a novel experimental gas turbine reheat combustor featuring both auto-ignition and propagation stabilised flame zones at atmospheric pressure. Dynamic pressure measurements at the faceplate of the reheat combustion chamber reveal high-amplitude periodic pressure pulsations at 3 kHz in the transverse direction of the rectangular cross-section combustion chamber. Further analysis of the acoustic signal shows that this is a thermoacoustically unstable condition undergoing limit-cycle oscillations. A sensitivity study is presented which indicates that these high-amplitude limit-cycle oscillations only occur under certain conditions: namely high power settings with propane addition to increase auto-ignition propensity. The spatially-resolved flame dynamics are then investigated using CH* chemiluminescence, phase-locked to the dynamic pressure, captured from all lateral sides of the reheat combustion chamber. This reveals strong heat release oscillations close to the chamber walls at the instability frequency, as well as axial movement of the flame tips in these regions and an overall transverse displacement of the flame. Both the heat release oscillations and the flame motion occur in phase with the acoustic mode. From these observations, likely thermoacoustic driving mechanisms which lead to the limit-cycle oscillations are inferred. In this case, the overall flame-acoustics interaction is assumed to be a superposition of several effects, with the observations suggesting strong influences from autoignition-pressure coupling as well as flame displacement and deformation due to the acoustic velocity field. These findings provide a foundation for the overall objective of developing predictive approaches to mitigate the impact of high-frequency thermoacoustic instabilities in future generations of gas turbines with sequential combustion systems.
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Wind, Torsten, Felix Güthe, and Khawar Syed. "Co-Firing of Hydrogen and Natural Gases in Lean Premixed Conventional and Reheat Burners (Alstom GT26)." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-25813.
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Addition of hydrogen (H2), produced from excess renewable electricity, to natural gas has become a new fuel type of interest for gas turbines. The addition of hydrogen extends the existing requirements to widen the fuel flexibility of gas turbine combustion systems to accommodate natural gases of varying content of higher hydrocarbons (C2+). The present paper examines the performance of the EV and SEV burners used in the sequential combustion system of Alstom’s reheat engines, which are fired with natural gas containing varying amounts of hydrogen and higher hydrocarbons. The performance is evaluated by means of single burner high pressure testing at full scale and at engine-relevant conditions. The fuel blends studied introduce variations in Wobbe index and reactivity. The latter influences, for example, laminar and turbulent burning velocities, which are significant parameters for conventional lean premixed burners such as the EV, and auto-ignition delay times, which is a significant parameter for reheat burners, such as the SEV. An increase in fuel reactivity can lead to increased NOx emissions, flashback sensitivity and flame dynamics. The impact of the fuel blends and operating parameters, such as flame temperature, on the combustion performance is studied. Results indicate that variation of flame temperature of the first burner is an effective parameter to maintain low NOx emissions as well as offsetting the impact of fuel reactivity on the auto-ignition delay time of the downstream reheat burner. The relative impact of hydrogen and higher hydrocarbons is in agreement with results from simple reactor and 1D flame analyses. The changes in combustion behaviour can be compensated by a slightly extended operation concept of the engine following the guidelines of the existing C2+ operation concept and will lead to a widened, safe operational range of Alstom reheat engines with respect to fuel flexibility without hardware modifications.
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Scarpato, Alessandro, Lisa Zander, Rohit Kulkarni, and Bruno Schuermans. "Identification of Multi-Parameter Flame Transfer Function for a Reheat Combustor." In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-57699.
Full textAbstract:
Lean premix technology is widely spread in gas turbine combustion systems, allowing modern power plants to fulfill very stringent emission targets. These systems are however also prone to thermoacoustic instabilities, which can limit the engine operating window. The thermoacoustic analysis of a combustor is thus a key element in its development process. GT24/GT26 reheat combustion system feature a unique technology where fuel is injected into a hot gas stream from a first combustor and auto-ignites in a sequential combustion chamber. Recently, a methodology was successfully developed and validated to analyze the dynamic response of an auto-ignition flame and to extract the Flame Transfer Function using unsteady Large-Eddy Simulations (LES) [GT2015-42622]. The flame was assumed to behave as a Single Input Single Output (SISO) system. The analysis qualitatively highlighted the important role of temperature and equivalence ratio fluctuations, but it was not possible to separate these effects from velocity perturbations. This is the main target of the present work: the flame is treated as a multi-parameter system, and compressible LES are conducted to extract the frequency-dependent flame transfer function. The simulations are forced with uncorrelated broadband signals in order to efficiently calculate the dynamic response over the frequency range of interest. The methodology introduced in this work will help to define stable operation concepts for gas turbines.
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Ciani, Andrea, John P. Wood, Anders Wickström, Geir J. Rørtveit, Rosetta Steeneveldt, Jostein Pettersen, Nils Wortmann, and Mirko R. Bothien. "Sequential Combustion in Ansaldo Energia Gas Turbines: The Technology Enabler for CO2-Free, Highly Efficient Power Production Based on Hydrogen." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-14794.
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Abstract Today gas turbines and combined cycle power plants play an important role in power generation and in the light of increasing energy demand, their role is expected to grow alongside renewables. In addition, the volatility of renewables in generating and dispatching power entails a new focus on electricity security. This reinforces the importance of gas turbines in guaranteeing grid reliability by compensating for the intermittency of renewables. In order to achieve the Paris Agreement’s goals, power generation must be decarbonized. This is where hydrogen produced from renewables or with CCS (Carbon Capture and Storage) comes into play, allowing totally CO2-free combustion. Hydrogen features the unique capability to store energy for medium to long storage cycles and hence could be used to alleviate seasonal variations of renewable power generation. The importance of hydrogen for future power generation is expected to increase due to several factors: the push for CO2-free energy production is calling for various options, all resulting in the necessity of a broader fuel flexibility, in particular accommodating hydrogen as a future fuel feeding gas turbines and combined cycle power plants. Hydrogen from methane reforming is pursued, with particular interest within energy scenarios linked with carbon capture and storage, while the increased share of renewables requires the storage of energy for which hydrogen is the best candidate. Compared to natural gas the main challenge of hydrogen combustion is its increased reactivity resulting in a decrease of engine performance for conventional premix combustion systems. The sequential combustion technology used within Ansaldo Energia’s GT36 and GT26 gas turbines provides for extra freedom in optimizing the operation concept. This sequential combustion technology enables low emission combustion at high temperatures with particularly high fuel flexibility thanks to the complementarity between its first stage, stabilized by flame propagation and its second (sequential) stage, stabilized by auto-ignition. With this concept, gas turbines are envisaged to be able to provide reliable, dispatchable, CO2-free electric power. In this paper, an overview of hydrogen production (grey, blue, and green hydrogen), transport and storage are presented targeting a CO2-free energy system based on gas turbines. A detailed description of the test infrastructure, handling of highly reactive fuels is given with specific aspects of the large amounts of hydrogen used for the full engine pressure tests. Based on the results discussed at last year’s Turbo Expo (Bothien et al. GT2019-90798), further high pressure test results are reported, demonstrating how sequential combustion with novel operational concepts is able to achieve the lowest emissions, highest fuel and operational flexibility, for very high combustor exit temperatures (H-class) with unprecedented hydrogen contents.
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Guyot, Daniel, Gabrielle Tea, and Christoph Appel. "Low NOx SEV Lean Premix Reheat Combustion in Alstom GT24 Gas Turbines." In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-43203.
Full textAbstract:
Reducing gas turbine emissions and increasing their operational flexibility are key targets in today’s gas turbine market. In order to further reduce emissions and increase the operational flexibility of its GT24 (60Hz) and GT26 (50Hz), Alstom has introduced an improved SEV burner and fuel lance into its GT24 upgrade 2011 and GT26 upgrade 2011 sequential reheat combustion system. Sequential combustion is a key differentiator of Alstom GT24 engines in the F-class gas turbine market. The inlet temperature for the GT24 SEV combustor is around 1000 degC and reaction of the fuel/oxidant mixture is initiated through auto-ignition. The recent development of the Alstom sequential combustion system is a perfect example of evolutionary design optimizations and technology transfer between Alstom GT24 and GT26 engines. Better overall performance is achieved through improved SEV burner aerodynamics and fuel injection, while keeping the main features of the sequential burner technology. The improved SEV burner/lance concept has been optimized towards rapid fuel/oxidant mixing for low emissions, improved fuel flexibility with regards to highly reactive fuels (higher C2+ and hydrogen content), and to sustain a wide operation window. In addition, the burner front panel features an improved cooling concept based on near-wall cooling as well as integrated acoustics damping devices designed to reduce combustion pulsations thus extending the SEV combustor’s operation window even further. After having been validated extensively in the Alstom high pressure sector rig test facility, the improved GT24 SEV burner has been retrofitted into a commercial GT24 field engine for full engine validation during long-term operation. This paper presents the obtained high pressure sector rig and engine validation results for the GT24 (2011) SEV burner/lance hardware with a focus on reduced NOX and CO emissions and improved operational behavior of the SEV combustor. The high pressure tests demonstrated robust SEV burner/lance operation with up to 50% lower NOX formation and a more than 70K higher SEV burner inlet temperature compared to the GT24 (2006) hardware. For the GT24 engine with retrofitted upgrade 2011 SEV burner/lance all validation targets were achieved including an extremely robust operation behavior, up to 40% lower GT NOX emissions, significantly lower CO emissions at partload and baseload, a very broad operation window (up to 100K width in SEV combustor inlet temperature) and all measured SEV burner/lance temperatures in the expected range. Sector rig and engine validation results have confirmed the expected SEV burner fuel flexibility (up to 18%-vol. C2+ and up to 5%-vol. hydrogen as standard).