Countercurrent shear flow control has been shown as an effective method of increasing volumetric heat release within a dump combustor due to an increase in turbulence, specifically the large turbulent structures present in the flow field. Limitations in a previous suction-derived control mechanism motivated developing this fluidic control scheme using a secondary momentum-driven source.
Multiple momentum-driven facilities were developed and explored; two facilities that showed promise are presented and the results of the isothermal studies show increases in turbulence and three-dimensionality. Momentum-driven countercurrent shear acts to increase the shear within the flow while simultaneously decreasing the convective velocity, thus resulting in elevated peak turbulence levels and increases in both the scale of the turbulent structures and the cross-stream averaged turbulence levels. The effects of this enhanced countercurrent shear leads to a globally unstable flow field that is quite advantageous in combustion control.
Linear stability theory was used to provide guidance into the global flow fields created within these facilities, all of which contain multiple unstable profiles, each having their own stability parameters. Dissecting the flow created into a series of unstable profiles and using knowledge of the stability of these parallel flow profiles provides insight into the global stability of the flows created and how these flows can be used for fluidic control within a dump combustor.
Future studies will investigate the confinement of this flow field and will explore the use of momentum-driven countercurrent shear within a dump combustor under premixed combustion. It is anticipated that the results of the momentum-driven control mechanism will mirror the effects of the suction based mechanism in reacting environments, specifically creating an enhanced combustor that has increased heat release rates and is less prone to combustion-related instabilities.
University of Minnesota Ph.D. dissertation. August 2011. Major: Mechanical Engineering. Advisor: Paul J. Strykowski. 1 computer file (PDF); xii, 253 pages, appendix A.
Anderson, Matthew J..
Global dynamics of a dump combustor using momentum-driven countercurrent shear control..
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