Finite element analysis for acoustic characteristics of combustion stabilization devices

The present study has proposed a numerical methodology based on harmonic analysis of the convective Helmholtz equation to predict acoustic characteristics of combustion chambers with passive stabilization devices such as baffle and acoustic resonators. In order to resolve complex geometries of the acoustic damping devices, a three-dimensional Galerkin finite element method with four-type hybrid elements is adopted. The acoustic energy dissipation in the laminar wall boundary layer is taken into account by a wall damping model based on acoustic admittance. Special effort is devoted to obtain quantified parameters for comparative evaluation of acoustic damping capacities: (1) eigenfrequency shift and damping factor ratio for baffles, and (2) absorption coefficient and conductance for acoustic resonators. The numerical results have been compared with measured data from two different acoustic tests for baffle and Helmholtz resonators, respectively, and demonstrate that the present method is capable of reproducing quantitatively acoustic behaviors of the damping devices in terms of the quantified parameters if the wall damping model is appropriately adjusted.