Rotational Temperature and Number Density Measurements of N2, O2, CO, and CO2 in a Hypersonic Flow Field Using Laser-Raman Spectroscopy

After successful laboratory measurements of the rotational temperature TR of N2, O2, CO, and CO2 at atmospheric pressure and room temperature and of N2 at 296, 215, and 163 K at an equivalent room temperature pressure of 10 torr, measurements of the rotational temperature of these gases were made in the hypersonic flow field produced by either a sonic orifice or a conical nozzle expansion. Radial profile measurements of TR were performed at two axial positions for the N2 nozzle flow field at a reservoir pressure of 10 atm. Agreement was obtained with the electron beam results of Beylich using appropriate reservoir scaling laws. The axial variation of N2 number density was determined for the nozzle source over a range of reservoir pressures 3.3 to 10 atm, and radial profiles at two axial locations were determined for the 10- atm condition. Agreement with the MOC calculations was excellent.