Effect of Cooling Liner on Acoustic Energy Absorption and Flame Response

Abstract

Gas turbine combustors with lean combustion injectors are prone to thermo-acoustic/combustion instabilities. Several passive techniques have been developed to control combustion instabilities, such as using Helmholtz resonators or viscous dampers using perforated liners that have potential for broadband acoustic damping. In this paper the role of single-walled cooling liners is considered in the damping of acoustic waves and on the flame transfer function in a sample bluff-body burner. Three liner geometries are considered: no bias flow (solid liner), normal effusion holes, and grazing effusion holes at 25° inclination. Cold flow experiments with speaker forcing are carried out to characterise the absorption properties of the liner and compared with an acoustic network model. The results show that whereas the bulk of the acoustic losses is due to the vortex recirculation zones, the liners contribute significantly to the absorption over a wide area of the frequency range. The flame transfer function gain is measured as a function of bias flow for a given operating condition of the burner. The experiments show that for the geometry considered, the global flame transfer function is little affected by cooling except in the case of the normal flow holes. Further analysis shows that whereas the total flame transfer function is not affected, the flame heat release becomes more spatially distributed along the axial length, and a 1D flame response shows distinct modes corresponding to the modal heat release locations.

LES for the Evaluation of Acoustic Damping of Effusion Plates

“…Despite the fact that simple numerical models to characterize those screens have been proposed [2][3][4] and successfully applied [1,5,6] also to relatively complex set-up under a wide range of flow condition, detailed CFD simulations [7][8][9] and large experimental campaigns [10][11][12][13] are more and more performed to increase the knowledge of the mechanisms ruling the phenomenon and expand the database of available geometries and flow conditions. Surprisingly the use of fully 3D computational technique did not push researchers to investigate more complex models including globally three dimensional flow and acoustic conditions.…”

Suppression of Combustion Instabilities in a Premixed Swirl Combustor with Acoustic Liner

“…Fig.1), by which the damping performance of the acoustic liner can be improved. Relevant topics had been comprehensively investigated and could review in literatures [28][29][30][31][32][33][34][35].Those works were almost focused on the absorption performance of perforated dampers in a pure airflow and very few of them were carried out under self-excited combustion oscillations [26,27,36]. It is necessary to study the performance of acoustic liner under self-sustained thermoacoustic instabilities.…”

Assessment of Numerical Tools for the Evaluation of the Acoustic Impedance of Multi-Perforated Plates

“…In the paper by Bhayaraju et al [7] an actual effusion cooled tubular combustor is considered. The purpose is the observation of the interaction between cooling air and the flame transfer function: it is reported a significant flame response variation increasing cooling air Mach number when normal holes are considered, while typical tilted film cooling holes are not observed to affect the flame, with an acoustic damping only slightly dependent on coolant Mach number.…”