https://doi.org/10.1007/s00340-022-07850-7

11. Mai 2022

For the experimental simulation of the reentry and propelled flight of space transportation systems, a piston-driven shock tunnel HELM (High Enthalpy Laboratory Munich) is in operation at the Institute of Thermodynamics at the Universität der Bundeswehr München. For a better characterization of the thermodynamic properties of the test gas in the nozzle during experiments and to obtain data for the numerical simulation of high-enthalpy flows, knowledge of the temperature within the nozzle reservoir and the flow velocity is required.

Laser-induced grating spectroscopy is predestined for single-shot measurements, even at high pressures and temperatures, as it enables a high signal-to-noise ratio even under difficult measurement conditions. Thus, this measurement technique can be used on intermittently operating experimental test benches such as shock tubes and shock tunnels to measure temperatures and flow velocities.

An optical measurement setup already successfully used on the shock tunnel HELM to measure temperatures via homodyne thermal laser-induced grating spectroscopy was extended to additionally measure flow velocities via heterodyne detection. The additional components required for this purpose were designed for the planned application at HELM and integrated into the optical setup on a double-diaphragm shock tube. The measurement results obtained are described in this paper.