Numerical prediction of interaction between combustion, acoustics and vibration in gas turbines

Abstract

The turbulent flame in the lean combustion regime in a gas turbine combustor generates significant thermo-acoustic instabilities. The flame can amplify fluctuations in the released heat, and thus in the acoustic field as well. The induced pressure oscillations will drive vibrations of the combustor walls and burner parts. Stronger fluctuating pressure results in stronger fluctuations in the wall structure. Due to fatigue the remaining life time of the hard ware will be reduced significantly. This paper investigates modeling of acoustic oscillations and mechanical vibrations induced by lean premixed natural gas combustion. The mutual interaction of the combustion processes, induced oscillating pressure field in the combustion chamber, and induced vibration of the liner walls are investigated with numerical techniques. A partitioned procedure is used here: CFX-10 for the CFD analysis and Ansys-10 for the CSD analysis are coupled to give insight into a correlation between acoustic pressure oscillations and liner vibrations. These results will be compared with the available experimental data. The data are gathered in a purpose built 500 kW/5 bar premixed natural gas test rig.