Les instabilités de combustion posent des problèmes récurrents dans les foyers de combustion et peuvent causer des dommages importants et irréversibles aux structures. Lʼaccumulation dʼénergie acoustique au voisinage des modes propres du système résulte dʼun couplage résonant entre les perturbations de pression et du taux de dégagement de chaleur dans la zone de réaction. La prévision de ces fréquences et du champ acoustique associé est importante pour optimiser la conception des systèmes de contrôle actif ou passif empêchant lʼamplification de ces instabilités. Dans cette étude, le banc de combustion CESAM est utilisé pour stabiliser des flammes propane–air swirlées partiellement prémélangées. Dans le tube de prémélange, les gaz frais sont injectés tangentiellement pour mettre en rotation lʼécoulement, la flamme étant stabilisée dans la chambre de combustion par un changement brusque de section. Le fond du tube de mélange est équipé dʼun système de contrôle dʼimpédance (ICS) permettant dʼajuster le coefficient de réflexion acoustique. Lʼacoustique de ce système de cavités couplées est étudiée analytiquement en prenant en compte lʼimpédance acoustique mesurée au fond du tube de prémélange et dans les lignes dʼalimentation. La longueur de la chambre est aussi modifiée pour examiner les effets de la géométrie sur ces prévisions. On montre que le tube de prémélange et la chambre peuvent être considérés comme acoustiquement découplés pour des valeurs faibles de lʼindice de couplage défini ici. Ceci nʼest cependant pas valable dans la région où les fréquences sont voisines. Dans ce cas, seule lʼanalyse de lʼamortissement de chacun des modes permet de déterminer si les deux cavités sont couplées ou non. Il est par conséquent possible de découpler acoustiquement deux cavités en jouant sur lʼindice de couplage ou bien en modifiant lʼamortissement de lʼune des cavités lorsque leurs fréquences propres sont proches.
When coupled to acoustics, unsteady heat release oscillations may cause recurrent problems in many combustion chambers, potentially leading to dramatic damages to the structure. Accumulation of acoustic energy around the eigenmodes of the combustor results from the resonant coupling between pressure disturbances in the flame region with synchronized heat release rate perturbations. Predicting these frequencies and the corresponding sound pressure field is a key issue to design passive or active control systems to prevent the growth of these instabilities. In this study, an acoustically controlled combustion test bench CESAM is used to stabilize a partially premixed swirling propane–air flame. In the premixing tube, reactants are injected tangentially to generate the swirling flow, the flame being stabilized in the combustion chamber by a sudden expansion of the cross section. The premixer backplane is equipped with an Impedance Control System (ICS) allowing to adjust the acoustic reflection coefficient at this location. Acoustics of the coupled-cavity system formed by the premixer and the combustion chamber is investigated analytically by taking into account the measured acoustic impedances at the premixer backplane and in the feeding lines. The chamber length is also modified to examine the effects of the geometry on these predictions. It is shown that the premixer and combustion chamber can be considered as acoustically decoupled for small values of the acoustic coupling index, defined in the article. This offers flexible solutions to control the pressure distribution within the combustor, except when these frequencies match. When the frequencies are close to each other, only the analysis of the damping of the different cavities enables to indicate whether the system is coupled or not. Modifying either the acoustic coupling index or the damping values featuring the same frequency appears then as alternative solutions to decouple cavities.
Mots clés : Combustion, Énergie acoustique
Franck Richecoeur 1, 2 ; Thierry Schuller 1, 2 ; Ammar Lamraoui 1, 2 ; Sébastien Ducruix 1, 2
@article{CRMECA_2013__341_1-2_141_0,
author = {Franck Richecoeur and Thierry Schuller and Ammar Lamraoui and S\'ebastien Ducruix},
title = {Analytical and experimental investigations of gas turbine model combustor acoustics operated at atmospheric pressure},
journal = {Comptes Rendus. M\'ecanique},
pages = {141--151},
publisher = {Elsevier},
volume = {341},
number = {1-2},
year = {2013},
doi = {10.1016/j.crme.2012.11.008},
language = {en},
}
TY - JOUR AU - Franck Richecoeur AU - Thierry Schuller AU - Ammar Lamraoui AU - Sébastien Ducruix TI - Analytical and experimental investigations of gas turbine model combustor acoustics operated at atmospheric pressure JO - Comptes Rendus. Mécanique PY - 2013 SP - 141 EP - 151 VL - 341 IS - 1-2 PB - Elsevier DO - 10.1016/j.crme.2012.11.008 LA - en ID - CRMECA_2013__341_1-2_141_0 ER -
%0 Journal Article %A Franck Richecoeur %A Thierry Schuller %A Ammar Lamraoui %A Sébastien Ducruix %T Analytical and experimental investigations of gas turbine model combustor acoustics operated at atmospheric pressure %J Comptes Rendus. Mécanique %D 2013 %P 141-151 %V 341 %N 1-2 %I Elsevier %R 10.1016/j.crme.2012.11.008 %G en %F CRMECA_2013__341_1-2_141_0
Franck Richecoeur; Thierry Schuller; Ammar Lamraoui; Sébastien Ducruix. Analytical and experimental investigations of gas turbine model combustor acoustics operated at atmospheric pressure. Comptes Rendus. Mécanique, Volume 341 (2013) no. 1-2, pp. 141-151. doi : 10.1016/j.crme.2012.11.008. https://comptes-rendus.academie-sciences.fr/mecanique/articles/10.1016/j.crme.2012.11.008/
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