Numerical Analysis of Thermoacoustic Instability during Combustion of a C2H6‒Air Mixture

We report a computational study of the effect of the initial temperature of the air‒fuel mixture on heat release pulsations during combustion of a pretreated ethane‒air mixture in a model burner device. Combustion processes are modeled using large eddy simulation (LES) with flamelet generated manifolds (FGMs). The amplitude of the air‒fuel mixture velocity pulsations at the inlet is 10%, and the pulsation frequency varies in the range from 150 to 600 Hz. The acoustic response is analyzed using the n‒τ flame model to account for the interaction of the flame front with the acoustic field. As a result, the dependences of heat release pulsations on the velocity pulsation frequency of the supplied mixture are obtained at initial temperatures of 300, 400, and 500 K. It is shown that with a change in the initial temperature of the mixture, the values of the peak frequencies of the pressure pulsations shift upwards by 3‒5%. This means that, for the same flow velocity pulsation frequencies at the inlet, the heat release pulsation amplitudes can vary severalfold with changes in the inlet air temperature.