Impact of the heat release distribution on high-frequency transverse thermoacoustic driving in premixed swirl flames

Abstract

Self-excited, high-frequency first transversal thermoacoustic instabilities in a cylindrical combustion chamber equipped with a premixed swirl-stabilized flame are investigated. Phase-locked image analysis of the phenomena shows the displacement of the flame and a higher burning rate in the region of elevated pressure. The impact of diffuser angle and fuel composition on the stability limits and the flame position is investigated. The Rayleigh-Index is computed for a threedimensional domain based on analytical flame transfer functions for experimentally obtained data of OH*-chemiluminescence as measure for the spatial heat release. Two models from different sources are applied, which describe the interaction between flame and acoustic locally. The axial dependence of the amplitude of the transversal mode is computed by a numerical model, which takes the temperature distribution inside the combustion chamber into account. The comparison of the Rayleigh-Index of different operation points shows a correlation with the stability limits for some, but not for all investigated configurations.

Injector-coupled transverse instabilities in a multi-element premixed combustor

“…21,22 The local heat release profile, which directly impacts the local Rayleigh integral, determines which of these mechanisms play a dominant role in the driving of transverse instabilities. [23][24][25] Transverse to longitudinal coupling is another pathway that has been widely studied. In this mechanism, the fluctuating transverse pressure field in the combustion chamber causes axial pressure disturbances at the end of the injector.…”

“…21,22 The local heat release profile, which directly impacts the local Rayleigh integral, determines which of these mechanisms play a dominant role in the driving of transverse instabilities. 23–25…”