Measurement and simulation of combustion noise and dynamics of a confined swirl flame

The combustion noise produced by a confined, turbulent, premixed swirl burner is predicted with large-eddy simulation of compressible, reacting flow. Characteristics-based state-space boundary conditions are coupled to the large-eddy simulation to impose precisely and independently from each other magnitude and phase of the acoustic reflection coefficients at the boundaries of the computational domain. The coupling approach proves to be accurate and flexible in regard to the estimation of sound pressure spectra in a confined swirl combustor for different operating conditions. The predicted sound pressure levels and its spectral distributions are compared to measurements. Excellent qualitative and quantitative agreement is achieved not only for a stable configuration but also for configurations that exhibit a thermoacoustic instability. This indicates that the flow and flame dynamics are reasonably well reproduced by the simulations.