Two-step approach for pressure oscillations prediction in gas turbine combustion chambers

Currently, gas turbine manufacturers frequently face the problem of strong acoustic combustion-driven oscillations inside combustion chambers. These combustion instabilities can cause extensive wear and sometimes even catastrophic damage of combustion hardware. This requires prevention of combustion instabilities, which, in turn, requires reliable and fast predictive tools. We have developed a two-step method to find a set of operating parameters under which gas turbines can be operated without going into self-excited pressure oscillations. As the first step, an unsteady Reynolds-averaged Navier-Stokes simulation with the flame speed closure model implemented in the OpenFOAM (R) environment is performed to obtain the flame transfer function of the combustion set-up. As the second step time-domain simulations employing low-order network model implemented in Simulink (R) are executed. In this work, we apply the proposed method to the Beschaufelter RingSpalt test rig developed at the Technische Universitat Munchen. The sensitivity of thermoacoustic stability to the length of a combustion chamber, flame position, gain and phase of flame transfer function and outlet reflection coefficient are studied.