| Description |
The aim of this short course is to present recent developments in modeling unsteady reacting flow phenomena, with particular emphasis on the occurrence of combustion instabilities coupled with acoustic modes of combustors, and methods of suppressing such instabilities through active control schemes. The course will review relevant fundamental conservation equations, including non-dimensional formulations used in numerical simulation, to demonstrate the important scaling relationships. Basic flame instability mechanisms that promote unsteady heat release will be covered in detail. Simplified flow fields and reaction mechanisms will be used to demonstrate the evolution of these flame instabilities as fully developed thermo-acoustic waves within the combustor. LES modeling with appropriate subgrid flame models will be used to investigate unsteady heat release in more complex flow configurations. Numerical issues related to solving the acoustics in subsonic flow configurations will be presented. Limitation of linearized wave equation solution and estimation of Rayleigh criterion will be discussed. Finally, methods of suppressing combustion instabilities through active control schemes, especially recent efforts on development of model-based active control schemes, will be presented.
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