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Thermoacoustic instabilities in can-annular combustors


Schematic of a can-annular combustor
Existing set-up that will be modified: the annulus will be replaced by a thin plate with openings

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. Detailed experimental investigations on the significance of the coupling between the cans are sparse in the literature. The few, very recent experimental observations shown that both global and localized self-sustained thermoacoustic modes can occur. An experimental investigation of the aero-acoustic coupling is the goal of this thesis.


Thesis description

This work aims at setting up an experimental test-rig for investigating the dynamics of can-annular systems by using electro-acoustic feedback. An existing experiment on annular combustors will be modified by assembling a coupling plate at the downstream end of a set of tubes. The design may be aided by finite element calculations. The designed plate will be manufactured and assembled on an existing set of tubes (the cans) equipped with loudspeakers and microphones. The acoustic response of the coupled set of cans will then be experimentally quantified while varying some key geometrical parameters.

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

Your profile

You are a motivated and hands-on 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, CAD, measurements with microphones, data processing.


Now! (01.03.2021)


Dr. Alessandro Orchini


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