In conventional gas turbines, acoustic oscillation usually occurs in the combustion chamber of the gas turbines during combustion process due to combustion instability and varieties. This acoustic oscillation may evolve into highly pronounced resonance. Such oscillation, which is also known as combustion chamber pulsations, can assume amplitudes and associated pressure fluctuations that subject the combustion chamber itself to severe mechanical loads that my decisively reduce the life of the combustion chamber and, in the worst case, may even lead to destruction of the combustion chamber.
Generally, a type of damper known as Helmholtz damper is utilized to damp the pulsations generated in the combustion chamber of the gas turbine. Currently, one of the main difficulties in utilization of such damper is the fact that the space available for these dampers is limited. One possible approach in addressing such situation is to place the damper on the outer side of the combustion chamber. In practice, the thermal expansion of the different layers composing the combustion chamber prevents directly applying such dampers.
A damping arrangement for reducing resonant vibrations in a combustion chamber of a gas turbine is disclosed in US2004/0248053A1, wherein the combustion chamber comprises an outer wall-surface part and an inner wall-surface part facing the combustion chamber, gastightly encloses an intermediate space, into which cooling air can be fed for purposes of convective cooling of the combustion chamber wall. At least one third wall-surface part is provided, which, with the outer wall-surface part, encloses a gastight volume. The gastight volume is connected gastightly to the combustion chamber by at least one connecting line. A gasket is welded at an end of the connecting line that is located in the gastight volume, and covers the outer wall surface part to provide gas tightness. With this gasket and connecting lines, the damping arrangement may compensate thermal expansion difference between the outer and inner wall-surface part in one direction.
A combustion chamber suitable for a gas turbine engine is provided in US2006/0123791A1, which comprise at least one Helmholtz resonator having a resonator cavity and a resonator neck in flow communication with the chamber interior. The Helmholtz resonator is fixed to an inner casing of the combustion chamber, with the resonator neck penetrating into the interior of the combustion chamber through an opening on the inner wall of the combustion chamber. An annular sealing member is provided around the outer periphery of the neck to provide gas tight seal between the neck and the opening. The neck provides limited relative axial movement of the neck with respect to the combustion chamber so that substantially no load is transferred from the resonator neck to the combustion chamber during engine operation.
A combustor for a gas turbine including at least one resonator is disclosed in WO2012/057994A2, which comprises an outer liner and an inner liner. The resonator is coupled to the outer liner. The combustor liner includes a throat extending from the base of the resonator penetrating into the combustion chamber through the inner liner and the outer liner. The combustor liner further includes a grommet assembly that allows for relative thermal expansion between the inner liner and the outer liner proximate the throat in a first direction along the axis of the throat and a second direction perpendicular to the first direction.
Even with above mentioned development in the pulsation damping field, there exist a large space to improve the compensation effect in eliminating thermal expansion difference.