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Proposing Institution

Lehrstuhl für Thermodynamik, TU München
Project Manager

Malte Merk
Boltzmannstr. 15
85748 Garching
Combustion noise is an undesirable by-product of combusion processes, generated by un-steady heat release rate of the flame. For confined turbulent flames, two contributionscan be distinguished: On the one hand, turbulent fluctuations of velocity or fuel concen-tration generate as a “source term” broad-band fluctuations of the heat release. On theother hand, the flame may be disturbed by acoustic waves impinging upon the flame. Thisacoustic-flame interaction is generally described by the flame transfer function (FTF) of thesystem, or by the corresponding scattering matrix.In general it is not possible to determine accurately the source terms without knowledgeof the flame dynamics (expressed in terms of the scattering matrix or the FTF), and viceversa. Furthermore, the sound pressure levels in a combustion chamber are determinednot only by the strength of combustion noise sources, but also the flame dynamics, andthe acoustic properties of plenum and combustor. Thus comprehensive thermo-acousticcharacterization of confined, turbulent flames requires to determine both the combustionnoise source as well as the scattering matrix or FTF.The overall objective of the proposed project is to develop methods that allow the concur-rent determination of the combustion noise source and the flame dynamics by combiningadvanced system identification (ASI) techniques with experiment or large eddy simulation.The main idea consists in modelling both flame dynamics and combustion noise by a poly-nomial approach based on the Box-Jenkins structure. This model may be considered asan extension of Finite Impulse Response (FIR) methods. This will make possible to pre-dict combustion noise of confined, turbulent flames even in situations where acoustic-flameinteractions are important – a case that cannot be handled well by existing methods. Fur-thermore, ASI will increase the accuracy and robustness of FTF or scattering matrix identi-fication in situations where combustion noise levels are high.

Impressum, Conny Wendler