Accession Number:

ADA386244

Title:

Behavior of a Round Cryogenic Jet at Below and Above the Critical Pressure

Descriptive Note:

Corporate Author:

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION HUNTSVILLE AL GEORGE C MARSHALL SPACE FLIGHT CENTER

Personal Author(s):

Report Date:

1998-01-01

Pagination or Media Count:

6.0

Abstract:

In an effort to investigate and understand the behavior of the injected cryogenic fluid and its environment, a high pressure chamber is used into which pure N2 He, and O2 fluids are injected. Several chamber media are selected including, N2, Me, and mixtures of CON2. The effects of chamber pressure ranging from a subcritical to a supercritical values at a supercritical chamber are photographically observed and documented near the injector hole exit region using a CCD camera illuminated by a short-duration back-lit strobe light. At low subcritical chamber pressures, the jets exhibit small surface irregularities that amplify downstream, looking intact, shiny, but wavy on the surface which eventually break up into irregularly-shaped small entities. Further increase of chamber pressure aids formation of many small droplets on the surface of the jet ejecting away only within a narrow region below the critical pressure of the injected fluid similar to a second wind-induced jet breakup - regime. Raising the chamber pressure, transition into a full atomization regime is inhibited by reaching near, but S slightly lower than, the critical pressure of the injectant where both surface tension and heat of vaporization are sufficiently reduced. The jet appearance changes abruptly at this point and remains the same to resemble a turbulent gas jet injection. The jet initial growth rate, is extracted from a large set of images and plotted with the available data on liquid fuel injection in diesel engine environment, turbulent incompressible, and variable density jets and mixing layers, creating a unique plot on its own. The jet spreading rate measurements agree well with a theoretical equation proposed for incompressible but variable density turbulent mixing layers by Papamoschou and Roshko 1 and follow the trend of that of Dimotakiss 2, thus quantitatively strengthening the gas-jet like appearance. Considering t

Subject Categories:

  • Thermodynamics
  • Jet and Gas Turbine Engines

Distribution Statement:

APPROVED FOR PUBLIC RELEASE