Effects of circular and non-circular nozzle exit geometries on subsonic and supersonic jet propagations
- 10 May 2022
- journal article
- research article
- Published by SAGE Publications in Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
- Vol. 237 (1), 209-229
- https://doi.org/10.1177/09544100221097537
Abstract
The mixing enhancement and core length reduction of a jet without significant loss of thrust are essential for reducing infrared radiation, mitigating aeroacoustic noise, improving combustion characteristics, and thrust vectoring. The jet mixing can be improved by manipulating the flow behavior. In subsonic and sonic jets, the flow manipulation may be achieved by utilizing nozzles with non-circular geometries that shed vortices of varying size due to their non-uniform azimuth curvatures. Non-uniform vortices generate differential spreading along the nozzle's perimeter, causing axis switching and improving entrainment characteristics. Therefore, the present study examines the effects of two non-circular nozzle exit shapes (elliptic and square) on the mixing augmenting efficacy at subsonic and sonic flow conditions. The circular nozzle is tested for comparison. Both quantitative and qualitative analyses evaluate the efficacy of nozzles with non-circular exit geometries. Among the configurations investigated, the elliptic nozzle is superior in shortening the potential core length and enhancing the jet spread. A maximum reduction of 18.75% in core length with rapid jet decay was accomplished with the elliptic nozzle. The measurement of pressure profiles at different streamwise locations reveals that the spread rate is greater for elliptic and square jets than their circular counterpart. The elliptic jet exhibits the highest spread along the minor-axis direction compared to the major-axis direction. The differential jet spread rate in the elliptical jet causes an early axis-switching--direct evidence of mixing augmentation. Shadowgraph images show the asymmetric pattern of shock cell structures and differential spreading in elliptic and square jets.Keywords
This publication has 32 references indexed in Scilit:
- Effect of primary jet geometry on ejector performance: A cold-flow investigationInternational Journal of Heat and Fluid Flow, 2011
- Experimental study of the near field and transition region of a free jet issuing from a sharp-edged elliptic orifice plateEuropean Journal of Mechanics - B/Fluids, 2007
- Investigation of the near-field structure of an elliptic jet using stereoscopic particle image velocimetryMeasurement Science and Technology, 2003
- The effect of aspect ratio on the near-field turbulent structure of elliptic jetsFlow Measurement and Instrumentation, 1994
- Vortex induction and mass entrainment in a small-aspect-ratio elliptic jetJournal of Fluid Mechanics, 1987
- Visualization of a forced elliptic jetAIAA Journal, 1986
- Pressure probes for fluid measurementProgress in Aerospace Sciences, 1975
- On density effects and large structure in turbulent mixing layersJournal of Fluid Mechanics, 1974
- Orderly structure in jet turbulenceJournal of Fluid Mechanics, 1971
- Further experimental results for three- dimensional free jets.AIAA Journal, 1967