Suppression of Flame Wrinkling by Buoyancy: The Baroclinic Stabilization Mechanism

Buoyancy forces are known to alter the burning velocity of a turbulent e ame by modifying the e ame wrinkling process. To quantify how e ame wrinkles are amplie ed or attenuated by buoyancy, a repeatable wrinkle of known size and amplitude is created in a premixed e ame by interacting the e ame with a vortex. Images of the wrinkle amplitude were obtained for microgravity conditions in the NASA Lewis Research Center 2.2-s drop tower and for 1-g conditions. Both thermodiffusively stable and unstable cases were considered. Results quantify the degree to which buoyancy suppresses the e ame wrinkling; when buoyancy is removed, the microgravity e ames have a wrinkle amplitude that is 2 ‐3 times greater than 1- g e ames. Flame stretch effects also are observed because the diffusionallyunstablee ameshavelargerwrinkleamplitudesthanthestablecases.Theparticleimagingvelocimetry velocity data show that two stabilizing mechanisms occur due to buoyancy: the conventional Rayleigh ‐Taylor mechanism and a baroclinic stabilization mechanism, which has not been observed previously in combustion processes. Measurements show that the e ame generates new vorticity, and this e ame-generated vorticity can help to suppress the e ame wrinkling.