Dan Fries
(Advisors: Prof. Suresh Menon & Prof. Devesh Ranjan]

will defend a doctoral thesis entitled,

Entrainment, Mixing, and Ignition in Single and Multiple Jets
in a Supersonic Crossflow

On

Tuesday, July 28 at 1:00 p.m.
Virtual Defense: https://bluejeans.com/740262117

Abstract
Non-reacting and reacting sonic jets in a supersonic crossflow are studied. The influence of injectant properties on turbulent mixing is investigated. Using pure gases, the molecular weight and specific heat ratio is varied between 4-44 g/mol and 1.24-1.66, respectively. The jet is injected into a Mach 1.71 crossflow with a stagnation temperature ~ 600 K. Two single jet injectors and two staged jet injectors are designed to characterize potential enhancements in turbulent mixing and combustion processes. Ignition locations on the symmetry plane of the flow field are evaluated for their ability to sustain chemical reactions/heat release. Mixture fraction and velocity fields are determined via Mie-scattering off solid particles. Velocity vectors are obtained by processing Mie-scattering image pairs with a correlation technique (particle image velocimetry). To ignite the flow field and enable systematic variation of the ignition location a traversable laser spark system is employed. The reacting flow is probed via CH* chemiluminescence and OH planar laser induced fluorescence visualizing regions containing hot products of combustion processes. A newly developed trajectory scaling improves correlation between all data sets considered, suggesting that the bow shock, boundary layer and momentum flux ratio are the dominant controlling factors. Turbulent mixing rates are highest for injectants with higher molecular weight. Results for the specific heat ratio suggest an influence of differences in convective velocities relative to crossflow and jet flows. The largest jet separation tested with the staged injectors yields the largest enhancements of turbulent mixing rates. Most favorable ignition locations lie in the windward jet shear layer away from the regions of highest flow strain. The smallest diameter single jet with presumably more boundary layer interaction and moderate strain rates provides the best results with regard to heat release after spark deposition. Trends suggest that moderate compressible strain rates and no flow expansion are advantageous to sustain heat release. Implications for future research directions and opportunities are discussed.

Committee

• Prof. Suresh Menon – School of Aerospace Engineering (advisor)
• Prof. Devesh Ranjan – School of Mechanical Engineering (advisor)
• Prof. Jerry Seitzman – School of Aerospace Engineering
• Prof. Adam Steinberg – School of Aerospace Engineering
• Dr. Timothy Ombrello – Senior Research Aerospace Engineer, Wright-Patterson AF Base, AFRL