A Hybrid Level-Set LES / CAA Method for Thermoacoustic Analyses
* Presenting author
Combustion instabilities limit the operating conditions of low-emission lean premixed com-bustion systems. To predict their onset a description of the unsteady heat release, which drives the thermoacoustic instability, and the acoustic flame response is necessary.Due to the scale disparity a hybrid approach is used for the investigation. The combustion process is computed by an unstructured cartesian LES solver. A conservative cut-cell tech-nique is used to capture arbitrary embedded boundaries. The computational grid is refined in the flame region to ensure a sufficient resolution of the turbulent scales. For the combustion process a combined G-equation progress variable modeling approach by Moureau et al.is applied. The G-equation approach is used to describe the motion of the inner-layer tem-perature contour of the flame, where the contour represents the zero-level set, i.e., the G = 0 contour. To lower the computational time an efficient parallel coupling method of the flow solver and the level-set solver based on a dual-mesh concept is used. In the second step of the hybrid approach the acoustic perturbation equations by Ewert and Schröder are solved to determine the acoustic field based on the sources computed from the LES data.