Flow Field Mapping of Carbon Dioxide Nozzle Expansion into Vacuum.

摘要

A series of tests has been completed at the Arnold Engineering Development Center (AEDC) to define the flow field of a nozzle plume in a hard vacuum. The purpose of these tests was to provide an experimental data base which could be used to verify currently available computer codes that are used to predict plume properties in the nozzle backflow region. Interest in such measurements derives from the fact that the currently available codes cannot accurately define nozzle flow in the backflow region of the nozzle where sensitive spacecraft surfaces and sensors can be positioned. In the present investigation, plume characteristics of carbon dioxide expansions from three 15- deg half-angle conical nozzles with a common exit diameter of 4 in. (10 cm) and area ratios of 16, 44.4, and 400 have been evaluated. A range of flow diagnostics including electron beam fluorescence, rotary liquid-nitrogen-cooled quartz crystal microbalance, free-molecule heat-transfer probe, free-molecule pressure probe, and a rotary pitot probe were used in this evaluation. Measurements of number density, rotational temperature, heat transfer, mass flux, flow angle, and pitot pressure are presented with a delineation of the effect that changes in lip geometry, chamber background pressure, and backflow cryopumping have upon nozzle plume properties. (Author).