Mathematical modeling of limit cycle thermoacoustic and hydrodynamic behavior of wedge shaped methane/hydrogen flames

Premixed gas turbine combustors are susceptible to combustion instabilities, which can yield in hardware damage. Acoustic waves produce oscillations in the unsteady heat release by perturbing the instantaneous equivalence ratio. Furthermore, many land based power generation units currently operate on natural gas many of them need to tackle the challenges due to a fuel switch towards synthesis gas in the near future. Operating conditions of a premixed gas turbine combustor is very sensitive to the changes in the fuel composition. G-equation is coupled with combustor acoustics in order to track the flame-front, which provides an understanding of dynamic flame holding and flashback behavior. Non-linear relation between acoustic velocity perturbations and equivalence ratio fluctuations is responsible for limit cycle behavior. Assuming a choked fuel injector these equivalence ratio perturbations are traced by seeding the axial airflow with massless particles. It is observed that these particles can cross both the injector and the flame a number of times due to reversal of flow during cycle instability. Behavior of a premixed confined conical hydrogen enriched methane flame is studied with regard to thermo-acoustic instability induced flame flashback and RMS pressure levels over a range of operating conditions.