Quantification of energy transformation processes between acoustic and hydrodynamic modes in non-compact thermoacoustic systems via a Helmholtz-Hodge decomposition approach

Thomas Hofmeister, Tobias Hummel, Bruno Schuermans, Thomas Sattelmayer

Publikation: Beitrag in Buch/Bericht/KonferenzbandKonferenzbeitragBegutachtung

5 Zitate (Scopus)

Abstract

Solutions of the Linearized Euler Equations (LEE) are composed of acoustic, entropy and vortical perturbation types. The excitation of the latter can be provoked by a transformation of acoustic into rotational energy, which originates from the interaction between acoustics and a mean flow shear-layer. This is known as acoustically induced vortex shedding and represents the phenomenon of interest in this study. In the field of thermoacoustics, numerical eigenfrequency simulations with the LEE have moved into focus to determine the acoustic damping rates associated with vortex shedding to complete thermoacoustic stability analyses of gas turbine combustors. However, there is yet no fundamental investigation existent, which establishes the legitimation to consider these LEE damping rates for this purpose. This question arises due to the implicit presence of vortical disturbances caused by vortex shedding next to the acoustic ones in LEE eigensolutions. In conclusion, the corresponding damping rates are not expected to represent the pure acoustic damping rates, which are exclusively required for a thermoacoustic stability analysis. The main objective of this work comprises the clarification, whether damping rates obtained by straightforwardly performed LEE eigenfrequency simulations can be used for a thermoacoustic stability assessment, although their eigen-solutions are ”polluted” by further disturbance types, i.e. the vortical one in this study. Therefore, a Helmholtz-Hodge decomposition approach is applied to LEE eigenmode shapes, which allows to explicitly access acoustic and vortical disturbance fields. These are used to extract the unambiguous, pure acoustic damping rates from LEE eigensolutions via evaluations of appropriate energy terms. The resulting damping rates are finally compared to the corresponding, original LEE damping rates and their experimental counterparts.

OriginalspracheEnglisch
TitelCombustion, Fuels, and Emissions
Herausgeber (Verlag)American Society of Mechanical Engineers (ASME)
ISBN (elektronisch)9780791858615
DOIs
PublikationsstatusVeröffentlicht - 2019
VeranstaltungASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition, GT 2019 - Phoenix, USA/Vereinigte Staaten
Dauer: 17 Juni 201921 Juni 2019

Publikationsreihe

NameProceedings of the ASME Turbo Expo
Band4A-2019

Konferenz

KonferenzASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition, GT 2019
Land/GebietUSA/Vereinigte Staaten
OrtPhoenix
Zeitraum17/06/1921/06/19

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