Thermoacoustic analysis of a laminar premixed flame using a linearized reactive flow solver

Abstract

In this paper, the dynamics and thermoacoustic stability of a laminar premixed flame are analyzed using a linearized reactive flow (LRF) solver. The LRF solver is based on linearized compressible Navier-Stokes and reacting species transport equations and thereby includes a model for the dynamic response of the flame to flow perturbations in an inherent manner. The equations are discretized using the discontinuous Galerkin finite element method. By way of example, thermoacoustic characteristics of attached and lifted laminar premixed flames are investigated. First, the respective flame transfer functions (FTFs) are computed in the frequency domain with the LRF solver. The results are in agreement with reference FTFs identified from CFD time-series. Secondly, the LRF solver is employed for thermoacoustic stability analysis, i.e. computation of shape, frequency, and growth rate of eigenmodes. Results are compared to established hybrid methods that couple FTFs with a low-order thermoacoustic network-model or a linearized Navier-Stokes equations solver. All solvers capture the dominant thermoacoustic mode, but only the LRF resolves local flow-flame interaction, revealing e.g. the onset of the flame movement and the propagation of distortions along the flame.