Vibration prediction in combustion chambers by coupling finite elements and large eddy simulations

To decrease NO x emissions from combustion systems, lean premixed combustion is used. A disadvantage is the higher sensitivity to combustion instabilities, leading to increased sound pressure levels in the combustor and resulting in an increased excitation of the surrounding structure: the liner. This causes fatigue, which limits the life time of the combustor. This paper presents a method to calculate these liner vibrations. The time-dependent pressures on the liner are calculated using large eddy simulation (LES) for both steady combustion and combustion with a pulsated fuel flow. These pressures are interpolated on a finite element grid and used in a transient analysis with a finite element model of the liner structure. The calculated vibrations agree well with experiments made on a 500 kW test rig.