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Quantitative measurement of density fluctuations with a full-field laser interferometric vibrometer

ABSTRACT: Modern, lean and premixed gas turbine combustion concepts for low NO(x) emissions are prone to combustion instabilities. In a previous work it was shown that laser interferometric vibrometry (LIV) can be used to record global as well as local heat release fluctuations in swirl-stabilized p...

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Autores principales: Greiffenhagen, Felix, Woisetschläger, Jakob, Gürtler, Johannes, Czarske, Jürgen
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Springer Berlin Heidelberg 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6882766/
https://www.ncbi.nlm.nih.gov/pubmed/31839691
http://dx.doi.org/10.1007/s00348-019-2842-y
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author Greiffenhagen, Felix
Woisetschläger, Jakob
Gürtler, Johannes
Czarske, Jürgen
author_facet Greiffenhagen, Felix
Woisetschläger, Jakob
Gürtler, Johannes
Czarske, Jürgen
author_sort Greiffenhagen, Felix
collection PubMed
description ABSTRACT: Modern, lean and premixed gas turbine combustion concepts for low NO(x) emissions are prone to combustion instabilities. In a previous work it was shown that laser interferometric vibrometry (LIV) can be used to record global as well as local heat release fluctuations in swirl-stabilized premixed methane flames quantitatively, if other effects influencing density are small. In this work a newly developed camera-based full-field LIV system (CLIV) was applied to a lean, confined, premixed and swirl-stabilized methane flame under atmospheric conditions. Instead of time-consuming pointwise scanning of the flame, CLIV records full-field line-of-sight density fluctuations with high spatio-temporal resolution. With a recording rate of 200 kHz, CLIV enables the visualization of highly unsteady processes in fluid dynamics and combustion research. As an example for an unsteady process, the propagation of the flame front through a lean, premixed gas volume is visualized during an ignition process. A discussion of algorithms and assumptions necessary to calculate heat release oscillations from density oscillations is presented and applied to phase-averaged data recorded with CLIV for this type of flame. As reference, OH* chemiluminescence data were recorded simultaneously. While density gradients travelling with the flow are recorded by LIV and CLIV, chemiluminescence imaging will show nothing in the absence of chemical reaction. GRAPHIC ABSTRACT: a Time-averaged density gradient within the combustor in lateral direction. b Density fluctuations along line-of-sight 7 ms after ignition. c Phase-averaged and local heat release fluctuations at 225 Hz perturbation frequency [Image: see text]
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spelling pubmed-68827662019-12-12 Quantitative measurement of density fluctuations with a full-field laser interferometric vibrometer Greiffenhagen, Felix Woisetschläger, Jakob Gürtler, Johannes Czarske, Jürgen Exp Fluids Research Article ABSTRACT: Modern, lean and premixed gas turbine combustion concepts for low NO(x) emissions are prone to combustion instabilities. In a previous work it was shown that laser interferometric vibrometry (LIV) can be used to record global as well as local heat release fluctuations in swirl-stabilized premixed methane flames quantitatively, if other effects influencing density are small. In this work a newly developed camera-based full-field LIV system (CLIV) was applied to a lean, confined, premixed and swirl-stabilized methane flame under atmospheric conditions. Instead of time-consuming pointwise scanning of the flame, CLIV records full-field line-of-sight density fluctuations with high spatio-temporal resolution. With a recording rate of 200 kHz, CLIV enables the visualization of highly unsteady processes in fluid dynamics and combustion research. As an example for an unsteady process, the propagation of the flame front through a lean, premixed gas volume is visualized during an ignition process. A discussion of algorithms and assumptions necessary to calculate heat release oscillations from density oscillations is presented and applied to phase-averaged data recorded with CLIV for this type of flame. As reference, OH* chemiluminescence data were recorded simultaneously. While density gradients travelling with the flow are recorded by LIV and CLIV, chemiluminescence imaging will show nothing in the absence of chemical reaction. GRAPHIC ABSTRACT: a Time-averaged density gradient within the combustor in lateral direction. b Density fluctuations along line-of-sight 7 ms after ignition. c Phase-averaged and local heat release fluctuations at 225 Hz perturbation frequency [Image: see text] Springer Berlin Heidelberg 2019-11-28 2020 /pmc/articles/PMC6882766/ /pubmed/31839691 http://dx.doi.org/10.1007/s00348-019-2842-y Text en © The Author(s) 2019 Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
spellingShingle Research Article
Greiffenhagen, Felix
Woisetschläger, Jakob
Gürtler, Johannes
Czarske, Jürgen
Quantitative measurement of density fluctuations with a full-field laser interferometric vibrometer
title Quantitative measurement of density fluctuations with a full-field laser interferometric vibrometer
title_full Quantitative measurement of density fluctuations with a full-field laser interferometric vibrometer
title_fullStr Quantitative measurement of density fluctuations with a full-field laser interferometric vibrometer
title_full_unstemmed Quantitative measurement of density fluctuations with a full-field laser interferometric vibrometer
title_short Quantitative measurement of density fluctuations with a full-field laser interferometric vibrometer
title_sort quantitative measurement of density fluctuations with a full-field laser interferometric vibrometer
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6882766/
https://www.ncbi.nlm.nih.gov/pubmed/31839691
http://dx.doi.org/10.1007/s00348-019-2842-y
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