Modelling of Intrinsic Thermoacoustic Instability of Premixed Flame in Combustors with Changes in Cross Section

This work investigates the effects of a moving flame front on the thermoacoustic oscillations in nonuniform combustors considering both the cavity and intrinsic resonant feedbacks. This theoretical study shows that the entropic perturbations can be generated by a perfectly premixed moving flame front in combustors with changes in cross section. Comparing with Direct Numerical Simulation (DNS) results shows the influence of the perturbation of a moving flame front on the intrinsic thermoacoustic stability. Applied to the verification of experimental results of a combustor consisting of multiple components, the present work predicts correctly the frequency and growth of both chamber resonant and intrinsic thermoacoustic (ITA) modes. Numerical research shows that alteration of reflection coefficients may both stabilize the chamber resonant and ITA modes of an experimental test rig. However, stabilizing the thermoacoustic oscillation by adjusting the boundary conditions seems less efficient in complicated combustion networks.