Hirsch C., Winkler A., Wäsle J., Sattelmayer T.

In the paper we demonstrate the calculation of the noise source of turbulent premixed swirl flames based on a new model using the time mean RANS variables from a reactive CFD calculation: heat release rate, turbulence kinetic energy and dissipation rate. The model is based on an assumed model spectrum for the reaction progress variable, on a premixed mean turbulent heat release model as well as on previous work on turbulent flame noise formation. It includes no free calibration coefficients. The new model has been validated with encourageing agreement using experimentally measured input data and comparing the resulting spectra of acoustic power with measurements on swirling flames varying power, equivalence ratio and fuel composition. Next, steady reactive RANS- CFD calculations were performed and validated to which the noise model was applied. Again very good agreement between the measured and modelled spectra of acoustic sound pressure was obtained. As the model contains no parameters that need to be adjusted to a specific application, it represents to our knowledge the first successful attempt to quantitatively predict the turbulent spectrum of heat release fluctuation in premixed flames and subsequently the acoustic power spectrum.