Thermo-acoustic instabilities in high power density gas turbine engines need to be understood to avoid unexpected shutdown events. This dissertation is focused on the combustor-turbine interaction for acoustic waves. The first part of the study is based on the acoustic reflection coefficient analysis, where the region of interest is located at the interface between the can-type combustion chamber and the first turbine stage. Simplified two-dimensional geometries and the corresponding three-dimensional engine alike turbine design have been investigated. The real engine case consists of a can-annular combustion chamber sector and the first vane section. Numerical simulation methods have been used and Compressible LES is applied based on the open source CFD package OpenFOAM. A forced response approach is applied imposing a sound wave excitation at the inlet of the combustion chamber. The applied Non-Reflecting Boundary Conditions are verified. Multi-harmonic excitation with small amplitudes is used. The post-processing for the geometries is performed using the two-microphone and the multi-microphone method. The numerical results obtained are compared to analytical formulae. In the second part of the work, the objective is to investigate the acoustic coupling between two neighboring cans in a can-annular combustor design. Measurements in such machines indicate that the pressure modes in neighboring cans synchronize and oscillate in or out of phase. This fact implies the existence of non-negligible cross-talk between neighboring cans and it justifies the usage of numerical methods to validate the experimental results. A forced response approach is used. A can-can transfer function has been computed to evaluate the percentage of the pressure waves transferred to the second can. Simplified 2D and 3D equivalent systems are investigated. Possible solutions able to reduce the cross-talk effect will be carried out and the accurate agreement between correspondent 2D and 3D configurations will justify the analysis of 2D systems to reduce CPU time. Finally an extension of the current solver into a moving-mesh combustion solver has been developed together with the generation of a 3D mesh. This solver could be used to couple more gas turbine components, leading to a more accurate analysis of the interaction between different engine parts.
|Award date||2 Dec 2016|
|Place of Publication||Enschede|
|Publication status||Published - 2 Dec 2016|