Heterogenous Gas-Wall-Interactions in high enthalpy Non-Equilibrium Flows

• Applicant: Professor Dr.-Ing. Georg Herdrich
• Subject Area: Fluid Mechanics
• Term: from 2020 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 432978288

• Final Report Year: 2024

Final Report Abstract

This project investigated heterogeneous catalytic recombination of atomic species on hightemperature materials in high-enthalpy non-equilibrium flows. SSiC and grade 5 titanium samples were exposed to pure oxygen and nitrogen plasma flows in the PWK3 plasma wind tunnel at the University of Stuttgart’s Institute of Space Systems. Key objectives included determining spectrally resolved emissivities during experiments using two infrared spectrometers (1-10 µm range). In-situ spectral emissivity measurements were demonstrated and compared with results from the IRS emissivity measurement facility. Comprehensive material characterization studies were conducted under various plasma conditions, with extensive flow characterization measurements using heat flux probes, pitot plasma probes, and TDLAS. The experiments were reconstructed numerically using the IRS CFD-code URANUS to determine global catalytic recombination coefficients. Inflow conditions were validated by simulating flow around a water-cooled copper heat flux probe. A PHLUX-type probe measured atomic oxygen fluxes in the fringe of a high-enthalpy oxygen flow, demonstrating its effectiveness in characterizing environments with moderate heat fluxes and high ATOX fluxes. The project showed that in-situ spectral emissivity measurements can improve surface heat flux analyses and recombination coefficient determinations. However, challenges with spectrometer calibration were noted. Further investigations with in-situ calibration and expanded test conditions could lead to more comprehensive finite-rate catalytic recombination models. Results were presented at conferences and published in peer-reviewed journals.

Publications

• In-situ emissivity assessment of grade 5 titanium in high-enthalpy flows for catalysis investigations. In: 73rd International Astronautical Congress (IAC). 2022
  C. F. Kaiser, H. Burghaus & G. Herdrich
  
• In-situ spectral emissivity assessment of Sintered Silicon Carbide (SSiC) in high-enthalpy flows for catalysis investigations. In: 2nd International Conference on Flight Vehicles, Aerothermodynamics & Re-entry Missions and Engineering (FAR). 2022
  C. F. Kaiser, H. Burghaus, A. S. Pagan & G. Herdrich
  
• Experimental Application of a Catalytic Heat Flux Probe in Venus Aerobraking and High-Altitude Earth Re-entry Environments. In: Journal of Evolving Space Activities 2.131 (2024)
  C. F. Kaiser, A. S. Pagan, H. Burghaus & G. Herdrich