Response of Gaseous Turbulent Jet Combustion to Transverse Acoustic Forcing

Abstract

The objective of this research was to investigate the flame dynamics of reacting turbulent non-premixed single and coaxial jets in unforced and acoustically forced environments. A gas-gas burner was used to create turbulent oxygen-enriched methane/air non-premixed flames at atmospheric pressure and temperature. Two different burner configurations were used: one having a single jet and one having a coaxial jet, both surrounded by the same co-flow. In this study, the flames were exposed to transverse acoustic waves in a rectangular channel, tuned to subject the flames to pressure antinode acoustic forcing at various frequencies and amplitudes. The flame responses were recorded using high speed Schlieren and OH* chemiluminescence imaging. To establish traceability between the single and coaxial flames, the center jet was set to be the same between the single jet and the coaxial jet at two different Reynolds numbers The annular flow of the coaxial jet was set to have the same bulk velocity as the co-flow. This created relatively benign conditions under which both flames might be expected to respond similarly. Despite this, the flame responses were considerably different, including the flame liftoff regimes. An analysis of the flow visualizations revealed subtle behaviors that can explain the differences.