A Novel Reheat Combustor Experiment for the Analysis of High-Frequency Flame Dynamics: Concept and Experimental Validation

Berger, Frederik; Hummel, Tobias; Vega, Pedro Romero; Schuermans, Bruno; Sattelmayer, Thomas

doi:10.1115/gt2018-77101

Cited by 10 publications

(8 citation statements)

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“…Another type of sequential combustor [1] features a flame that is stabilized substantially downstream of the fuel injector in order to ensure good mixing of the fuel with the vitiated flow before the former is consumed, and it falls into the category of partially-premixed combustion. The response of these flames to different types of perturbation, such as acoustic velocity [16,17] or temperature fluctuations [18][19][20] have been investigated numerically in the context of thermoacoustic instabilities in sequential combustors [21,22].…”

Section: Introductionmentioning

confidence: 99%

Combustion regimes in sequential combustors: Flame propagation and autoignition at elevated temperature and pressure

Schulz

Noiray

2019

Combustion and Flame

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This numerical study investigates the combustion modes in the second stage of a sequential combustor at atmospheric and high pressure. The sequential burner (SB) features a mixing section with fuel injection into a hot vitiated crossflow. Depending on the dominant combustion mode, a recirculation zone assists flame anchoring in the combustion chamber. The flame is located sufficiently downstream of the injector resulting in partially premixed conditions. First, combustion regime maps are obtained from 0-D and 1-D simulations showing the co-existence of three combustion modes: autoignition, flame propagation and flame propagation assisted by autoignition. These regime maps can be used to understand the combustion modes at play in turbulent sequential combustors, as shown with 3-D large eddy simulations (LES) with semi-detailed chemistry. In addition to the simulation of steady-state combustion at three different operating conditions, transient simulations are performed: (i) ignition of the combustor with autoignition as the dominant mode, (ii) ignition that is initiated by autoignition and that is followed by a transition to a propagation stabilized flame, and (iii) a transient change of the inlet temperature (decrease by 150 K) resulting into a change of the combustion regime. These results show the importance of the recirculation zone for the ignition and the anchoring of a propagating type flame. On the contrary, the autoignition flame stabilizes due to continuous self-ignition of the mixture and the recirculation zone does not play an important role for the flame anchoring.

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Section: Introductionmentioning

confidence: 99%

Combustion regimes in sequential combustors: Flame propagation and autoignition at elevated temperature and pressure

Schulz

Noiray

2019

Combustion and Flame

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“…Flame stabilisation in the homogeneous core flow is dominated by auto-ignition while the shear layers in the upper and lower regions are mostly stabilised by propagation, although it should be noted that autoignition activity is still present in these zones. 26 Longitudinal modes are suppressed by two components: Firstly, the orifice increases damping of longitudinal modes due to the reduced cross-section at the mixing section inlet and conversion of acoustic energy to vorticity, 28 while transverse modes are unaffected due to the aforementioned upstream attenuation. Secondly, a nozzle increases convective damping at the combustor outlet.…”

Section: Methodsmentioning

confidence: 99%

Observation of reactive shear layer modulation associated with high-frequency transverse thermoacoustic oscillations in a gas turbine reheat combustor experiment

McClure

Berger

Bertsch

et al. 2022

International Journal of Spray and Combustion Dynamics

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This paper presents the investigation of high-frequency thermoacoustic oscillations and associated flame dynamics in an experimental gas turbine reheat combustor at atmospheric pressure. Examination of dynamic pressure measurements reveals bursts of high-frequency periodic oscillations which appear randomly amidst stochastic fluctuations in the reheat combustor. Analysis of the flame dynamics during these bursts of periodic behaviour reveals that increased heat release in the reactive shear layers of the reheat flame is associated with greater thermoacoustic driving potential. This redistribution of heat release is likely due to the stochastic nature of auto-ignition kernel formation. To determine the underlying flame-acoustic coupling mechanism behind the driving potential, phase-resolved flame dynamics over the acoustic cycle are investigated which reveal the presence of an oscillatory heat release pattern associated with the first transverse eigenmode. An in-phase interaction between the acoustic field and these heat release oscillations in the shear layer regions indicates that this phenomenon likely constitutes a thermoacoustic driving mechanism. This is an important step towards the development of models for high-frequency thermoacoustic driving mechanisms relevant to reheat combustion systems, which will allow accurate prediction and mitigation of thermoacoustic instabilities in future designs.

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“…Several studies analyzed flame stabilization mechanisms in second stage flames featuring a jet-in-crossflow configuration [10,11] where [10] used H 2 -rich fuels. In sequential combustion configuration [12][13][14][15][16][17][18][19] used natural gas/air mixtures. It was demonstrated using LES that flame stabilization is governed by autoignition and propagation combustion regimes [12].…”

Section: Introductionmentioning

confidence: 99%

Effect of Mixing on the Anchoring and Combustion Regimes of Pure Hydrogen Flames in Sequential Combustors

Solana-Pérez

Shcherbanev

Ciani³

et al. 2022

Journal of Engineering for Gas Turbines and Power

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In this work we perform an experimental study of the combustion of pure hydrogen in the sequential stage of a generic combustor. This academic test rig is a simplified model of an industrial sequential combustor. The sequential fuel is injected using different injector geometries. The composition and temperature of the hot stream at the inlet of the sequential burner are defined by the mass flows of the hot combustion products from the first stage and of the dilution air. This temperature is varied between 1100 K and 850 K by modifying the dilution air mass flow in order to study the different combustion regimes of the sequential hydrogen flame. High-speed imaging of OH radicals chemiluminescence is performed with optical emission spectroscopy to measure vitiated gas temperatures. We investigate the transition from a flame anchored in the sequential combustion chamber, to one stabilized upstream into the mixing section, when the inlet flow temperature is increased. Of particular interest is the increasing rate of formation of autoignition kernels in this transition process. The underlying combustion regime change is analyzed with 0D reactor simulations, and the limitations of such a simplified low-order model of the flame location are discussed. The effects and importance of the mixing process between fresh fuel and the hot vitiated co-flow is examined. Two different injectors are compared under the same operating conditions that provide different degrees of mixing and allow to demonstrate the impact of mixing quality on the flame morphology.

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A Novel Reheat Combustor Experiment for the Analysis of High-Frequency Flame Dynamics: Concept and Experimental Validation

Cited by 10 publications

References 0 publications

Combustion regimes in sequential combustors: Flame propagation and autoignition at elevated temperature and pressure

Combustion regimes in sequential combustors: Flame propagation and autoignition at elevated temperature and pressure

Observation of reactive shear layer modulation associated with high-frequency transverse thermoacoustic oscillations in a gas turbine reheat combustor experiment

Effect of Mixing on the Anchoring and Combustion Regimes of Pure Hydrogen Flames in Sequential Combustors

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