Swirl flow response to transverse and axial acoustic forcing

Abstract

The present study is an experimental investigation on the effect of axial and transverse acoustic forcing on a generic swirl flow. The aim is to provide a qualitative understanding of typical swirl flow response to transverse acoustic forcing, for a better understanding of the response of swirl-stabilized flames to the same configuration of acoustic forcing. The latter is critical for the ongoing research on thermoacoustic instability in annular gas turbine combustors. A single burner test-rig with transverse extensions to facilitate transverse acoustic modes is employed in this experimental study. The swirl flow, established using a generic radial swirl generator, features vortex breakdown. Two transverse forcing configurations are studied: a) symmetric forcing which leads to a pressure antinode at the burner, and, b) antisymmetric forcing which results in a velocity antinode at the burner location. The study is based on results from planar streamwise and crosswise flow field measurements. We find that while the symmetric forcing configuration causes a flow response similar to axial forcing, antisymmetric forcing results in a helical response.

Keywords

• annular combustors
• transverse acoustic forcing
• swirl flows