Near- and far-field plume studies of a one-kilowatt arcjet

Abstract

To support studies of transport in arcjet plumes, axial and radial profiles of electron temperature, electron number density, stagnation pressure, and flow field were obtained over an extensive volume of the plume of a 1-kW arcjet operating on hydrogen. All experiments were performed in a 6 by 9 m vacuum chamber at a tank pressure of less than 4 x 10 ~4 torr during arcjet operation. Electron temperatures obtained spectroscopically 1.2 cm downstream of the exit plane ranged from 0.10 to 0.13 eV, while electron number densities determined ~2 cm downstream of the exit plane via langmuir probe varied between 0.3-1 x 10 12 cm~3. Far-field langmuir probe measurements showed that a rapid radial variation in electron number density exists, ranging from 0.5 to 5 x 10 9cm~3, and from 0.5 to 2 x 10 9 cm~3, 30 and 88 cm downstream of the exit plane, respectively. Electron temperatures at these axial locations show much less of an axial dependence, ranging between 0.070.20 eV at both axial positions. Finally, an impact pressure probe was used to measure the radial profiles of stagnation pressure 53 and 64 cm from the exit plane as well as flow angle. The impact pressure probe data compare favorably with stagnation pressures predicted by a source-flow code and suggests that the heavy particles diffuse less radially than do the electrons.