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

Abstract

This study assesses and compares two alternative approaches to determine the acoustic scattering matrix of a premixed turbulent swirl combustor: (1) The acoustic scattering matrix coefficients are obtained directly from a compressible large eddy simulation (LES). Specifically, the incoming and outgoing characteristic waves f and g extracted from the LES are used to determine the respective transmission and reflection coefficients via System Identification (SI) techniques. (2) The flame transfer function (FTF) is identified from LES time series data of upstream velocity and heat release rate. The transfer matrix of the reactive combustor is then derived by combining the FTF with the Rankine–Hugoniot (RH) relations across a compact heat source and a transfer matrix of the cold combustor, which is deduced from a linear network model. Linear algebraic transformation of the transfer matrix consequently yields the combustor scattering matrix. In a cross-comparison study that includes comprehensive experimental data, it is shown that both approaches successfully predict the scattering matrix of the reactive turbulent swirl combustor.

Domain decomposition method based on One-Way approaches for sound propagation in a partially lined duct

“…The fact that this result is continuous even across the interfaces is an indication about the good approximation of the pseudo-eigenvectors matrices used for the projection and the good convergence of the iterative process used for the domain decomposition. Having access to this decomposition into left-going and right-going components provides direct access to the scattering matrix that is used to evaluate the performance of acoustic liners [38,39] and other configurations [40,41]. This scattering matrix can be expressed in the following relation:…”

Incompressible versus compressible large eddy simulation for the identification of premixed flame dynamics

“…The established way in thermoacoustic studies to identify such a flame response is to use either experiment [5][6][7][8] or compressible large eddy simulation (LES) [9][10][11][12] , where the flame is acoustically forced with a harmonic or broadband signal from an upstream or downstream position. Simultaneously, the velocity perturbations at the reference position and the global heat release signal are monitored.…”

“…The acoustic response of turbulent premixed burners can be described by a single-input-single-output 3 black box model, with velocity perturbations at a reference position as input and global heat release rate response as output. Given that perfectly premixed flames or configurations with an acoustically stiff fuel injector located very close to the burner outlet 4 are studied, the flame response is defined as The established way in thermoacoustic studies to identify such a flame response is to use either experiment 5–8 or compressible large eddy simulation (LES) 9–12 , where the flame is acoustically forced with a harmonic or broadband signal from an upstream or downstream position. Simultaneously, the velocity perturbations at the reference position and the global heat release signal are monitored.…”