Research Initiation Award: Combustion in an Asymmetric Configuration

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The objective of this project is to understand the interaction of combustion and shear layer control techniques. The proposal is to study the fluid mechanics of combustion of a small aspect ratio rectangular channel sudden expansion. This configuration utilizes a combination of several control techniques. Active forcing will be used to drive the system's acoustic resonances and to organize the shear layer vortical structures for phase locked analysis. Passive forcing will be introduced via the configuration geometry; the elliptic vortex rings formed in the shear layer undergo self-induction, deforming the jet cross section and introducing transverse velocities not found in plane and axi-symmetric configurations. The approach is experimental, using laser doppler anemometry and flow visualization to examine the velocity field and premixed flame in a rectangular sudden expansion. The equivalence ratio will range from lean, where the stabilization of the flame in the shear layer downstream of the backward facing step is affected by the passive, active and three dimensional control techniques, to rich, where the flame/flow interaction is dominated by acoustic resonances. This will allow determination of the extent to which these control methods are effective in this configuration. The study will be initially limited to premixed combustion. The results can later be extended to address issues in nonpremixed combustion such as the optimization of fuel injection locations to take advantage of the flowfields produced by the control techniques. This research is expected to have a significant impact on combustion applications ranging from industrial pulse combustors and toxic waste incinerators to subsonic and supersonic combustion in ramjets. The understanding of the effects of shear layer control techniques on mixing and combustion can produce immediate results in increased combustion efficiency and control.