During the reentry of a spacecraft into the earth's atmosphere velocities up to 11 km/s occur as a function of the light path. The kinetic energy of the reentry body is converted into internal energy of the gas by compression shocks and gas friction. Complex chemical and physical processes occur, resulting in very high gas temperatures. In the development of reusable spacecraft, these aerothermodynamic loads are of crucial importance for the design of the systems and components. Although the development of new aircraft is today mainly based on CFD simulations, the complexity of the fows makes experiments indispensable at different times in the development process. The experimentally determined data are for example used for the validation of calculation results or for the further development of the calculation algorithms. For the experimental simulation of high-enthalpy flows, plasma wind tunnels enable continuous hot gas tests with medium heat loads. The thermal energy is generally supplied to the gas by an electric arc so that the chemical composition of the test gas is normally not influenced by the combustion of hydrocarbons. This property is an essential prerequisite for the development of thermal barrier coatings for aerospace technology. Today, optical measurement techniques are almost exclusively used to analyze the chemical and physical processes in the gas. Depending on the selected measurement method, different variables of the flow field can thus be detected. 1D Raman spectroscopy, for example, enables the determination of line-shaped flow field properties, so that in addition to the gas temperature, their gradients can be detected simultaneously. The application of 1D Raman spectroscopy to high-enthalpy flows has so far been strongly limited due to the low light intensity of the experimental setups used. The present work describes the development of a new 1D Raman spectroscopy method with a significant increase in the light intensity of the experimental setup using narrow band interference filters. The method is first compared with the classical 1D Raman spectroscopy with spectrographs and is evaluated using the achievable signal-to-noise-and-interference-ratio. The results of temperature measurements of the hot gas of the plasma wind tunnel of the University of the Federal Armed Forces Germany in Munich are then presented at various operating points of the test facility and their similarity is shown. The experimental investigations were accompanied by stationary 3D CFD simulations. For this purpose, detailed reaction kinetics with the Dunn and Kang air chemistry model was implemented into a commercially available CFD program and the suitability of various turbulence models for the simulation of high enthalpy jets was investigated. Large differences between the different simulation results as well as the deviations of the simulation results from the experiment led to the fact that the simulation did not yield any significant results. The high demands placed on the numerical simulation of such flows are thus illustrated.    «

During the reentry of a spacecraft into the earth's atmosphere velocities up to 11 km/s occur as a function of the light path. The kinetic energy of the reentry body is converted into internal energy of the gas by compression shocks and gas friction. Complex chemical and physical processes occur, resulting in very high gas temperatures. In the development of reusable spacecraft, these aerothermodynamic loads are of crucial importance for the design of the systems and components. Although the dev...    »