New Technique for Temperature and Specie Concentration Measurements in UnseededSupersonic and Hypersonic Gas Flows

摘要

The goal was to develop an experimental diagnostic technique suitable for gasflows of densities intermediate between atmospheric and rarefied. A laser assisted Electron Beam Fluorescence technique which we call electron photon fluorescence was developed. Theoretical work was done to predict the time dependence of the excitation/deexcitation processes. As described in the original proposal, our goal in this work was the attainment of an experimental diagnostic technique suitable for gas flows of densities intermediate between atmospheric and rarefied. Measurements in such intermediate density flows, typical of hypersonic flight at altitudes above about 50 km, present difficulties in that traditional wind-tunnel techniques (shadow and schlieren, as well as laser based scattering techniques) provide insufficient signal. Moreover, the resonant scattering techniques may require an absorptive species as a tracer to be seeded into the flow, a requirement inconsistent with the realities of existing large facilities. On the other hand, the densities are not enough for continuous electron-beam fluorescence (EBF) to be used due to beam spreading and collisional quenching.