Numerical Investigations of the Noise Sources Generated in a Swirl Stabilized Flame

Compressible Large Eddy Simulations (LES) have been performed to study the reacting flow field of a typical industrial double concentric swirl burner. A turbulent flame speed closure (TFC) was implemented into the code to model the premixed flame. The results have been analysed with respect to the acoustic sources used in Lighthill's acoustic analogy. It is shown, that the noise sources generated by the combustion process are significantly larger than the sources caused by the aerodynamics. A spectral analysis allowed to detect two dominant frequencies in the swirling flow field, which are suspected to contribute to the noise emissions. The frequencies are caused by the eigenfrequency of the burner and an oscillating coherent structure near the burner outlet.