Development of acoustic-enhanced damping configurations for gas turbine combustion systems

Combustion instabilities can be self-excited through a feedback loop between unsteady heat release and acoustic pressure oscillations. Furthermore, whilst low emission lean burn systems are attractive due to reduced NOx emissions, their application may be restricted due to their increased sensitivity to these instabilities.Combustion instabilities cover a range of frequencies and modes that are dependent upon the engine operating conditions and geometry. However, passive acoustic dampers may potentially be used to control the instabilities by damping the pressure pulsations; although, multiple dampers may be required to cover the entire range of frequencies with sufficient damping. Geometrically large cavities and cooling flows through the dampers result in systems that are challenging to design within the strict geometric and operating envelopes of gas turbine aero-engines. Thus,novel passive damping systems that can offer a consistent acoustic response, but with a reduced space requirement or cooling flow, are highly attractive. [Continues.]