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Effects of a Diverging Cup on Swirl Number, Flow Pattern, and Topology of Premixed Flames

Degenève, Arthur and Jourdaine, Paul and Mirat, Clément and Vicquelin, Ronan and Caudal, Jean and Schuller, Thierry Effects of a Diverging Cup on Swirl Number, Flow Pattern, and Topology of Premixed Flames. (2019) Journal Of Engineering For Gas Turbines And Power, 141 (3). 031022. ISSN 0742-4795

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Official URL: https://doi.org/10.1115/1.4041518

Abstract

Impact of the diverging cup angle of a swirling injector on the flow pattern and stabiliza- tion of technically premixed flames is investigated both theoretically and experimentally with the help of OH* chemiluminescence, OH laser-induced fluorescence and particle image velocimetry (PIV) measurements. Recirculation enhancement with a lower position of the internal recirculation zone (IRZ) and a flame leading edge protruding further upstream in the swirled flow are observed as the injector nozzle cup angle is increased. A theoretical analysis is carried out to examine whether this could be explained by changes of the swirl level as the diffuser cup angle is varied. It is shown that pressure effects need in this case to be taken into account in the swirl number definition and expressions for changes of the swirl level through a diffuser are derived. It is demonstrated that changes of the swirl level including or not the pressure contribution to the axial momentum flux are not at the origin of the changes observed of the flow and flame patterns in the experi- ments. The swirl number without the pressure term, designated as pressure-less swirl, is then determined experimentally with laser Doppler velocimetry (LDV) measurements at the injector outlet for a set of diffusers with increasing quarl angles under nonreacting conditions and the values found corroborate the predictions. It is finally shown that the decline of axial velocity and the rise of adverse axial pressure gradient, both due to the cross section area change through the diffuser cup, are the dominant effects that control the leading edge position of the IRZ of the swirled flow. This is used to develop a model for the displacement of the recirculation bubble as the quarl angle varies that shows very good agreement with experiments. [DOI: 10.1115/1.4041518]

Item Type:Article
HAL Id:hal-01917151
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:Other partners > Air Liquide (FRANCE)
French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UT3 (FRANCE)
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Deposited On:09 Nov 2018 09:42

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