Measurement and Simulation of Combustion Noise and Dynamics of a Confined Swirl Flame

Abstract

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.

Direct Assessment of the Acoustic Scattering Matrix of a Turbulent Swirl Combustor by Combining System Identification, Large Eddy Simulation and Analytical Approaches

“…The chemistry of the perfectly premixed methane/air flame is described by a same LES setup is used as in Ref. [32], for which the LES was validated. However, the need in the current study of properly measuring the acoustic fluctuations downstream requires the test rig to be equipped with an additional pipe that contains the mounted microphones ME, ME 0 , and ME 00 (see Fig.…”

Prediction of combustion noise of an enclosed flame by simultaneous identification of noise source and flame dynamics

“…Thus, a laminar velocity profile is imposed at the inlet. For further details and validation of the LES setup, the reader is referred to [8] .…”

“…if the LES generates sp~nous heat release rate fluctuations), erroneous noise models will result, independent of the chosen mode) structu~e. For the current study the validity of the LES w1th respect to the combustion noise generation was validated in [8] by comparing LES results against measured sound pressure spectra. Note that to a certain extent the combustion noise ~eneration is in~ependent from the flame dynam-1cs.…”

“…Obviously, sound pressure levels in a combustion system may be determined by measurement [6][7][8] . However, experiments are rather laborious and inflexible in regard to changes in the acous-tic boundaries.…”

“…However, experiments are rather laborious and inflexible in regard to changes in the acous-tic boundaries. Reactive compressible Large-Eddy Simulation (LES) resolves directly the combustion noise generation as well as the acoustic propagation and reflection within the cavity and has proven itself to be capable of reproducing accurately the sound pressure spectra in confined systems [8][9][10] . Even though changes in the acoustic boundaries are feasible to implement, the computational effort of LES is considerable, and the investigation of a wide range of parameters, say, is prohibitively expensive.…”