Investigation of Equivalence Ratio Fluctuations on the Dynamics of Turbulent Lean Premixed Methane/Air Flames with a Linear-Eddy Model

Heat release fluctuations generated by equivalence ratio fluctuations may interact with the acoustics of a gas turbine combustion chamber leading to unwanted combustion instabilities, which remains a critical issue in the development of low emission, lean premixed gas turbine combustors. The present article addresses this topic by numerical investigations of one-dimensional lean premixed methane/air flames subject to prescribed sinusoidal equivalence ratio fluctuations. Compared to previous investigations, we focus on turbulent conditions and emission predictions using the one-dimensional linear-eddy model (LEM) and detailed chemistry. Within the limitations of the one-dimensional LEM the approach allows to investigate the fully non-linear regime of flame response to equivalence ratio fluctuations under turbulent conditions. Results for different forcing amplitudes and turbulence levels indicate a strongly non-linear behavior for high forcing amplitudes.