An experimental investigation of transverse injection from circular and elliptical nozzles into a supersonic crossflow
Gruber, Mark Robert
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https://hdl.handle.net/2142/21262
Description
Title
An experimental investigation of transverse injection from circular and elliptical nozzles into a supersonic crossflow
Author(s)
Gruber, Mark Robert
Issue Date
1996
Doctoral Committee Chair(s)
Dutton, J. Craig
Department of Study
Mechanical Science and Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Aerospace
Engineering, Mechanical
Language
eng
Abstract
Flowfields created by transverse injection of helium and air through circular and elliptical nozzles into a supersonic crossflow have been investigated experimentally using nonintrusive optical diagnostics and intrusive probe-based measurement techniques. Four injectant gas/injector geometry combinations were investigated with each case being operated at a jet-to-freestream momentum flux ratio (J) of 2.9. Instantaneous shadowgraph visualizations were produced for each case allowing examination of the flowfield's shock structure and the global characteristics of the jet/freestream interaction. Rayleigh/Mie scattering from silicone dioxide particles seeded into the moist freestream air allowed the collection of ensembles of digital images from several measurement planes in each case; end view planes were examined at four streamwise locations and the spanwise centerplane was investigated extensively. Pitot and concentration probes were used at two end view planes in the two cases using helium as the injectant gas.
Instantaneous images show a highly three-dimensional interaction dominated by large- and small-scale vortices. Analyses of the image ensembles provide mean and standard deviation statistics, lateral spreading and transverse penetration characteristics, large-scale mixing information, two-dimensional spatial correlation fields, pertinent bow and separation shock features, and large-scale convection velocity measurements. Results indicate that the elliptical nozzle produces a jet with greater lateral spread than does the jet from the circular nozzle, while the transverse penetration is significantly suppressed. Injectant molecular weight does not strongly affect the jet's transverse penetration, although it leads to substantial compressibility differences that dramatically influence the characteristics of the large-scale structures formed in the shear layer and the entrainment and mixing occurring between the injectant and crossflow. Mixing layer fluctuations present in air injection cases (low compressibility) intrude deeper into the jet fluid as compared to helium injection cases (high compressibility), where these fluctuations are confined near the jet edge. Probe-based measurement techniques provide quantitative comparisons of the total pressure losses and time-averaged mixing characteristics in these injection flowfields. Results indicate slight performance differences between the two injector geometries that suggest better near-field mixing and slightly lower total pressure losses in the elliptical injection flowfield.
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