Flame Transfer Function Measurements With CH4 and H2 Fuel Mixtures at Ultra Wet Conditions in a Swirl Stabilized Premixed Combustor

Schimek, Sebastian; Göke, Sebastian; Schrödinger, Christina; Paschereit, Christian Oliver

doi:10.1115/gt2012-69788

Cited by 5 publications

(3 citation statements)

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“…The potential utility of this approach, in reducing the significant complexity associated with the reacting flow to a simple response function, has resulted in considerable effort in understanding the behaviour, scaling and generality of such functions [6][7][8][9][10][11].…”

Section: V04at04a066-1mentioning

confidence: 99%

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Flame Transfer Functions and Dynamics of a Closely Confined Premixed Bluff Body Stabilised Flame With Swirl

Nygård

Worth

2020

Volume 4A: Combustion, Fuels, and Emissions

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The Flame Transfer Function (FTF) and flame dynamics of a single, highly swirled, closely confined, premixed flame is studied over a wide range of operating conditions at a fixed perturbation level at the dump plane. The equivalence ratio and bulk velocity are varied in order to examine the important ratio of flame height to velocity in scaling the flame response function. The enclosure geometry is kept constant, and therefore due to the close confinement and varying flame height, strong flame-wall interactions are present for some operating conditions. The effect of these interactions on the FTF due to changes in the “relative” or “effective confinement” of the flame can therefore be studied. When the equivalence ratio is sufficiently high, and therefore the effective confinement sufficiently small, modulations, or dips, in the gain and phase of the FTF are observed, due to interference of the perturbations created at the swirler and at the dump plane. Due to the small length scales and relatively high velocities in the current configuration, the dip is at a high frequency and spans a wide range of frequencies compared to similar studies which have previously identified similar phenomena. It is also observed that when the equivalence ratio was decreased, increasing the effective confinement, a critical point is reached where the modulations are suppressed. This is linked to a temporal shift in the heat release rate at the downstream location where the flame impinges on the combustion chamber walls during the oscillation cycle. The shift causes a decrease in the expected level of interference, demonstrating that the effective confinement is an important parameter to consider for the nature of the FTF response. Additionally, a Distributed Time Lag (DTL) model with two distinct time lags, capturing the swirler perturbations and the perturbations at the inlet, is successfully applied to the FTFs. The model provides a simple way to accurately capture the two dominant time scales in the problem without the need of prior knowledge of the cause of the perturbations, and a simple expression to recreate the complex valued FTF. In addition the model also provides insight into the time scales of the problem, demonstrating in the current work that time scales recovered from the DTL analysis are offset from simple Strouhal number scaling, due to the effects of increasing effective confinement.

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Section: V04at04a066-1mentioning

confidence: 99%

“…This use of multiple scaling parameters is similarly taken by Sattelmayer [17] with multiple Distributed Time Lags (DTLs). This approach has been used successfully for example by Schuermans et al [18] and Schimek et al [11] who use two DTLs to model both equivalence ratio and acoustic oscillations.…”

Section: V04at04a066-1mentioning

confidence: 99%

Flame Transfer Functions and Dynamics of a Closely Confined Premixed Bluff Body Stabilised Flame With Swirl

Nygård

Worth

2020

Volume 4A: Combustion, Fuels, and Emissions

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“…It must be also noticed that the use of these numerical findings for design purposes should also be supported by a detailed validation phase against experiments [15]. Instead, in literature, there has been little direct comparison [18][19] and, in the most of cases, it is limited to lab-scale tests or not relevant operating conditions .…”

Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Characterization of the Self-Excited Dynamics Behavior of a Technically Premixed Burner

Meloni¹,

Gori²,

Riccio³

et al. 2022

Volume 3B: Combustion, Fuels, and Emissions

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In this paper, the numerical findings of a high fidelity CFD model will be compared with the experimental data of a test campaign devoted at characterizing the performance of a technically premixed industrial burner regarding the thermoacoustic instabilities. The data are retrieved at relevant gas turbine conditions in a test bench where the flame tube can change its length during the test execution allowing its fundamental acoustic frequencies to be modified and, in case, triggered. Mimicking the test configuration, several Large-Eddy Simulations are performed with different lengths of the flame tube in order to verify the ability of the numerical model to reproduce the excited dominant frequency and the corresponding limit cycle amplitude measurements. The numerical model demonstrates the ability to correctly reproduce the frequency triggered during the test and to reach different limit cycle amplitudes along different flame tube lengths in agreement with the tests, as well. However, it is found that the amplitude of the acoustic pressure fluctuation during the limit cycle is generally under-predicted. Despite this, the proposed approach demonstrates to be a robust tool for the characterization of a given design, allowing to dramatically reduce the computational cost of the analysis, at least in the early design phase. Since the numerical model can correctly reproduce the behavior of the investigated design, a deep post-processing of the solutions is performed to shed light on the physical mechanisms sustaining the thermo-acoustic instability. Among the numerical techniques employed at this purpose, the Phase-Locked Average and the Extended-POD are applied trying to correlate the fluctuations of the different quantities inside the premixed channel of the burner and the primary zone as well.

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Flow Field and Flame Dynamics of Swirling Methane and Hydrogen Flames at Dry and Steam Diluted Conditions

Steffen

Krüger

Paschereit

2014

Journal of Engineering for Gas Turbines and Power

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The majority of recent stationary gas turbine combustors employ swirling flows for flame stabilization. The swirling flow undergoes vortex breakdown (VB) and exhibits a complex flow field including zones of recirculating fluid and regions of high shear intensities. Of ten, self-excited helical flow instabilities, which manifest in a precession of the vortex core, are found in these flows and may influence the combustion process in beneficial and adverse ways. In the present study, we investigate the occurrence and shape of self-excited hydrodynamic instabilities and their impact on heat release fluctuations and mixing characteristics over a wide range of operating conditions. We employ high-speed stereoscopic particle image velocimetry (S-PIV) and simultaneous OH*chemiluminescence imaging to resolve the flow velocities and heat release distribution, respectively. The results reveal four different flame shapes: A detached annular flame, a long trumpet shaped flame, a V flame, and a very short flame anchored near the combus tor inlet. The flame shapes were found to closely correlate with the reactivity of the mix ture. Highly steam-diluted or very lean flames cause a detachment, whereas hydrogen fuel leads to very short flames. The detached flames feature a helical instability, which, in terms of frequency and shape, is similar to the isothermal case. A complete suppression of the helical structure is found for the V flame. Both the trumpet shaped flame and the very short flame feature helical instabilities of different frequencies and appearances. The phase-averaged OH*-chemiluminescence images show that the helical instabilities cause large-scale heat release fluctuations. The helical structure of the fluctuations is exploited to use a tomographic reconstruction technique. Furthermore, it is shown that the helical instability significantly enhances the mixing between the emanating jet and the central recirculation zone.

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Flame Transfer Function Measurements With CH4 and H2 Fuel Mixtures at Ultra Wet Conditions in a Swirl Stabilized Premixed Combustor

Cited by 5 publications

References 0 publications

Flame Transfer Functions and Dynamics of a Closely Confined Premixed Bluff Body Stabilised Flame With Swirl

Flame Transfer Functions and Dynamics of a Closely Confined Premixed Bluff Body Stabilised Flame With Swirl

Experimental and Numerical Characterization of the Self-Excited Dynamics Behavior of a Technically Premixed Burner

Flow Field and Flame Dynamics of Swirling Methane and Hydrogen Flames at Dry and Steam Diluted Conditions

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