Evaluation of StarCCM+ to predict thermoacoustic instabilities using Large Eddy Simulation

Indlekofer, Thomas
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"Self-sustained pressure and heat-release oscillations yielded by thermoacoustic coupling are a major problem of gas turbine operation and methods to predict them are needed. This work investigates the capabilities of Large Eddy Simulation (LES) in StarCCM+ to predict these instabilities in the academic Volvo bluff-body combustor. First, simplified cases are studied to assess boundary condition treatment and numerical accuracy of the methods available. The non-reactive operating point is predicted accurately, showing good agreement for velocity fields as well as the ability to predict the vortex shedding frequency in the intrinsically unsteady region of the recirculation zone. For a reacting-stable operating point the acceleration downstream of the bluff body is overpredicted and the flow fields are not predicted accurately. Low frequency oscillations of the unstable operating points are evidenced coincididing with experimental results and an acoustic analysis based on Comsol Multiphysics. Up to = 1:0 the coherence of the equivalence ratio and the magnitude of the instabilities is predicted qualitatively."