A Real-Time Combustion Instability Simulation with Comprehensive Thermo-Acoustic Dynamic Model

The thermo-acoustic instability in the combustion process of a gas turbine is caused by the interaction of the heat release mechanism and the pressure perturbation. These acoustic vibrations cause fatigue failure of the combustor and decrease the combustion efficiency. This study aims to develop a segmented dynamic thermo-acoustic model to understand combustion instability of a gas turbine. Then, the combustion instability was designed using the acoustic heat release model, and the designed instability model was segmented using the finite difference method, to evaluate the characteristics of flame propagation at each node. The combustion instability model was validated using experimental data to verify the instability amplitude. Also, the optimal node number was determined using the adiabatic flame temperature response. 10 nodes were selected in this study. A sensitivity analysis showed the predicted instability amplitude decreased when the nodes increased until node 4, due to heat generation. However, above 4 nodes the amplitude decreased, since the combustion outlet was directly connected to the ambient. As a result, the segmented combustion instability model was able to evaluate the flame propagation characteristics more accurately and found the largest area of instability was near the flame area.