| Abstract |
The research activities in FLUISTCOM are towards improved understanding of transient combustion and its coupling with combustor wall vibration. The objective is to come to well-validated models of transient combustion and wall vibration. This can lead to designs and design rules of combustors that are extremely robust even in combustion oscillatory situations. The reliable operation at low flame temperatures and accordingly extremely low nitric oxide emissions in large-scale power generation will be supported this way.
A clear lack of a joint research effort in the field of thermoacoustic oscillations on the structure of combustion systems has been identified. Research especially on the correlation between vibration amplitudes of the structure and the acoustic pressure amplitudes are not known in the field of combustor design. In particular issues related to the highly safety critical range of high-frequency oscillations (above 700 Hz) is not much understood: damping mechanisms of combustion systems and interaction with the liner structure.
However, for the design of more reliable and robust combustor designs the correlation between acoustic pressure amplitudes and structure vibration amplitudes is strongly required. Moreover, it is of high interest to know how this correlation of fluid/structure interaction will be affected by different parameters such as the shape of the liner, by the mounting of the elements, and by reinforcement. General methods for damping of structure vibrations form a central strategy towards a more reliable and robust liner and hence must be developed.
In order to address these central design issues for a robust combustor liner a detailed investigation of the fluid/structure interaction will be carried out within FLUISTCOM. A detailed study of the fluid structure interaction will be performed in a lab scale test rig. Both experimental measurements and numerical calculations will be carried out to determine the correlation between acoustic pressure oscillations on the one side and liner vibrations on the other side. Since reliability concern not only mechanical but also thermal loading the lab scale must also comprise experimental and numerical analysis concerning conjugate heat transfer of fluid/structure interaction. Measurements will be performed with pressure transducers and accelerometers mounted on the liner. The lab scale investigation should provide criteria for the design of gas turbine combustor liner and should provide experimental data to validate numerical codes addressing the fluid/structure interaction.
Special development of codes will focus on the interaction of fluid dynamics and the structure vibration. New interfaces between numerical combustion codes, thermo-acoustic codes on the one side and Finite element codes concerning mechanical stress and solid vibrations on the other side will be developed. Since up to now commercial codes do not offer such interfaces these fluid/structure interfaces should be of generic nature to be implemented in commercial CFD and Finite Element (FE) codes. The integrated/coupled analysis is a prerequisite for a stable/robust structural mechanical design. The interfaces will be validated on the small lab scale set up.
The codes are applied to evaluate different design options for more robust gas turbine combustor liners. Mechanical and thermal fluid/structure interactions are both significantly affected by the pressure level. Therefore, high-pressure tests are performed at different thermodynamic conditions representing the whole operation envelope using down selected liner designs. The numerical analysis will be applied to further optimise designs with respect to increase the damping of the structure vibration. |
