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Thermoacoustic instabilities in can-annular combustors


Schematic of a can-annular combustor
Coupled oscillator system that will be considered. The "springs" and "masses" represent the acoustics of a can and their (weak) coupling.

Thermoacoustic instabilities arise due to the constructive feedback between unsteady heat release fluctuations and combustor acoustics. They are strongly undesirable, as they lead to unwanted structural vibrations, thus limiting the operating range of the engine. The last generation (H-class) of gas turbines features can-annular combustor architectures. In these combustors, each flame burns in an essentially isolated manner in a can. Nonetheless, the annular turbine inlet, which is shared by all cans, couples the cans via acoustic phenomena. On an abstract level, the thermoacoustic dynamics of a can-annular combustor can then be characterized as a ring of weakly coupled self-excited oscillators. One oscillator represents an acoustic mode of an isolated can, driven by its flame, and weak coupling is provided by the gap between two cans at the turbine inlet.



Thesis description

This work aims at investigating theoretically and numerically the dynamics of can-annular systems. The acoustic response in each can will be approximated with an harmonic oscillator. The acoustic coupling between the cans will be modelled by means of both reactive and resistive coupling terms. The goal is that of linking the parameters that drive the oscillators/coupling to the geometrical/acoustic parameters of a real system, and investigate with time-domain simulations the fully coupled response of the system.

The research outcome has the potential to be published in major scientific journals.

Your profile

You are a motivated and creative student, happy to work in a team and with good communication skills. Applicants for this position are expected to have a background in Mechanical Engineering or Physics, and about to finish their Master's studies. Ideally, you have experience in one or more of the following:  acoustics, numerical integration of ODEs, Galerkin method.


Now! (01.03.2021)


Dr. Alessandro Orchini


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