Accession Number:

ADA611068

Title:

Receptivity of a Cryogenic Coaxial Liquid Jet to Acoustic Disturbances

Descriptive Note:

Technical paper Jan-May 2014

Corporate Author:

AIR FORCE RESEARCH LAB EDWARDS AFB CA AEROSPACE SYSTEMS DIRECTORATE

Report Date:

2014-01-01

Pagination or Media Count:

13.0

Abstract:

The receptivity of cryogenic coaxial gas-liquid jet flows to transverse acoustic disturbances has been explored experimentally. Liquid nitrogen in the inner jet and cooled helium in the outer annular jet were used to simulate an oxygenhydrogen liquid rocket engine injector. The flow is submerged in a chamber that experiences a transverse acoustic resonance. The shear coaxial jet is exposed to a variety of acoustic conditions including different frequencies, amplitudes, and locations within the resonant mode shape. High-speed back-lit images were captured to record the behavior of the natural unforced and forced coaxial jets. Proper orthogonal decomposition and spectral analysis were used to extract natural and forced modes. Convective modes are extracted, and a new Strouhal number is used to characterize the strongest natural convective mode that is analogous to the preferred mode in free jets. The threshold of receptivity was found for a number of different injector flows and acoustic forcing conditions. The results indicate that the dimensionless frequency plays an important role, and there exists finite forcing amplitude at which the threshold of receptivity occurs. The receptivity threshold provides useful insight on the suitability of a given injector design for specific rocket combustion chamber conditions.

Subject Categories:

  • Acoustics
  • Fluid Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE