Geometry Effects on Steady and Acoustically Forced Shear-Coaxial Jet Sprays
Abstract
This experimental study investigated the mixing behavior and characteristics of dynamic flow structures of cryogenic, non-reactive shear-coaxial jet sprays under varying flow conditions, with and without the presence of pressure perturbations due to acoustic forcing transverse to the flow direction. The role of injector geometry was examined using shear-coaxial injectors with different outer-to-inner jet area ratios and different inner jet post thickness to inner jet diameter ratios. Flow conditions spanning a high pressure spray (reduced pressure of 0.44) ranging up into the supercritical regime (reduced pressure of 1.05), with varying outer-to-inner jet momentum flux ratios (0.5-20), and maximum or minimum amplitude in the pressure perturbation at the jet axis location were considered. Nitrogen was used as the test fluid. The inner and outer jet temperatures were independently controlled so that the inner condensed flow was cooled down to below saturation temperature of the liquid, and to below the critical temperature for the supercritical fluid. Back-lighting the coaxial spray/supercritical jet resulted in a silhouette of the dense inner core, which appeared as a dark column. This distinguished it from the outer gaseous flow, and thus, enabled high speed images to capture the jet flow dynamics. Dark-core, pertaining to the unmixed portion of the dense inner flow, and length measurements were used to indicate the extent of mixing under the different flow conditions and injector geometries. As expected, increasing the momentum flux ratio resulted in shorter dark-core lengths. However, the extent of influence of momentum flux ratio was dependent on the injector geometry, whereby, the dark-core length of a large outer-to-inner jet area ratio injector flow was more influenced by increasing momentum flux ratios. A small area ratio injector flow, on the other hand, showed a more gradual decrease in its dark-core length with increasing momentum flux ratios.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2012
- Accession Number
- ADA593841
Entities
People
- Douglas G. Talley
- Ivett Leyva
- Juan I. Rodriguez
- Sophonias Teshome
Organizations
- Air Force Research Laboratory