Laser Induced Fluorescence and Diode Laser Absorption Spectroscopy Measurements in CO/CO2 Hypersonic Flow of LBK

Abstract

In the frame of the ESA TRP study ‘CFD Validation in CO2 Environment’ aerothermodynamic tests were performed in DLR’s arc heated facility L2K in Cologne using two different cylindrical models with diameters of 50 and 100 mm. For the correct simulation of the Martian atmosphere a gas mixture of 97% carbon dioxide and 3% nitrogen was used. Tests were carried out at two flow conditions characterized by enthalpy levels of 13.1 and 8.3 MJ/kg. The flow field was characterized by Pitot pressure profile and cold wall heat flux measurements. In addition to emission measurements laser-induced fluorescence (LIF) of nitrous oxide and carbon monoxide was applied, in order to get space-resolved rotational temperatures and partial densities in free stream regions and the shock layer in front of the models. Diode laser absorption spectroscopy (DLAS) was used to deduce the translational temperature, the velocity and the density of carbon monoxide in free stream flow. Velocities are measured with good accuracy, while the translational temperature measurements tend to be too high. Online velocity determinations with a repetition rate of 10 Hz were performed and resulted in free stream velocities.