Einfluss der Selbstentzündung auf die Antriebsmechanismen hochfrequenter Verbrennungsinstabilitäten vorgemischter turbulenter Flammen.
Technische Thermodynamik
Zusammenfassung der Projektergebnisse
The project investigated the occurrence of high-frequency thermoacoustic instabilities in gas turbine reheat combustion systems. Such instabilities often occur late in design or after commissioning where addressing these issues is extremely costly. As a result, thermoacoustic stability assessments are becoming increasingly important in early design phases. The goal of the project was to determine the underlying flame-acoustic interaction mechanisms which drive thermoacoustic oscillations in reheat flames in order to support predictive models. A thermoacoustic driving mechanism based on the local modulation of the autoignition delay time by acoustic perturbations was proposed and modelled numerically. The results of the modelling indicate that this mechanism represents significant driving potential when regions of high acoustic pressure amplitudes overlap with the autoignition flame. Comparison with experimental measurements confirms this as a key driver of thermoacoustic instabilities in reheat flames. The experiments also revealed additional driving mechanisms associated with shear layer modulation due to acoustically-induced vortex shedding and flame displacement and deformation by the acoustic velocity field. The shear layer modulation mechanism is highly geometry dependent and is limited by the fact that vortex shedding is also a source of acoustic dissipation. Furthermore, the conditions in real combustors will likely further reduce the driving potential of this mechanism relative to the autoignition delay modulation mechanism. Finally, flame displacement and deformation have been observed however their contribution is weaker than the previous two mechanisms. This suggests that flame displacement and deformation are secondary driving mechanisms in reheat flames and should not be neglected; however, driving under real engine conditions is expected to be dominated by the autoignition delay modulation mechanism.
Projektbezogene Publikationen (Auswahl)
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Self-Excited High-Frequency Transverse Limit-Cycle Oscillations and Associated Flame Dynamics in a Gas Turbine Reheat Combustor Experiment. Volume 3B: Combustion, Fuels, and Emissions. American Society of Mechanical Engineers.
McClure, Jonathan; Berger, Frederik M.; Bertsch, Michael; Schuermans, Bruno & Sattelmayer, Thomas
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High-Frequency Mode Shape Dependent Flame-Acoustic Interactions in Reheat Flames. Volume 3A: Combustion, Fuels, and Emissions. American Society of Mechanical Engineers.
McClure, Jonathan; Bothien, Mirko & Sattelmayer, Thomas
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Observation of reactive shear layer modulation associated with high-frequency transverse thermoacoustic oscillations in a gas turbine reheat combustor experiment. International Journal of Spray and Combustion Dynamics, 14(1-2), 131-142.
McClure, Jonathan; Berger, Frederik M.; Bertsch, Michael; Schuermans, Bruno & Sattelmayer, Thomas
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Autoignition delay modulation by high-frequency thermoacoustic oscillations in reheat flames. Proceedings of the Combustion Institute, 39(4), 4691-4700.
McClure, Jonathan; Bothien, Mirko & Sattelmayer, Thomas
