Profile of an anisentropic nitrogen nozzle expansion

Hypersonic N2 flow fields were produced using a conical nozzle of 1.04 mm throat diameter and an exit plane area ratio of 13.4. The reservoir pressure was varied over the range of 1.93 to 13.6 atm at the reservoir temperature of 285 K, and the reservoir conditions were such that both isentropic and anisentropic conditions existed within the axial region investigated. The N2 number density and rotational temperature axial and radial profiles were measured using laser Raman scattering, and comparisons are presented with the method of characteristics isentropic prediction. The onset of condensation and subsequent cluster growth were observed using laser Rayleigh scattering and depolarization measurements as well as photographic recording. The Rayleigh and Raman scattering data were used to obtain estimates of the axial variation of the cluster size as well as the variation of the depolarization ratio with the mean number of molecules of the cluster.