Characterization of High-Enthalpy-Flow Environment for Ablation Material Tests Using Advanced Diagnostics

For reliable material qualification in high-enthalpy flows, detailed characterization of material and flow parameters is essential. Therefore, the flowfield of arc-heated facility L3K, which has been intensively used for ablation material tests in Europe, has been characterized using advanced diagnostic tools. For the first time, the complete flow chain from the reservoir to the freestream and shock layer has been studied using sophisticated measurement techniques. Rotational and vibrational temperatures of nitrogen molecules were measured in the reservoir, freestream, and shock layer using coherent anti-Stokes Raman scattering. In addition, the temperatures of nitric oxide molecules in the freestream were measured by means of laser-induced fluorescence. Emission spectroscopy provided quantitative data of shock-layer temperatures. For the measurement of the freestream velocity and electron density, a microwave interferometer has been used. In addition, the pitot pressure and cold wall heat flux rate have been measured by means of intrusive probes. Parallel to the experimental investigation, numerical rebuilding of the flowfield has been conducted by using the TAU code developed at German Aerospace Center (DLR). The results of the multitemperature model provide further insight into the flow physics of the facility.