Investigation of the Free-Stream Plasma Flow Produced by an ICP Wind Tunnel

The free-stream air plasma jet produced by the Plasmatron facility at the von Karman Institute for Fluid Dynamics is investigated. Intrusive and non-intrusive measurement techniques are combined to characterize the plasma flow for a set of operating conditions relevant to the actual atmospheric entry environment. The High Speed Camera imaging technique is applied to investigate the unsteadiness features of the plasma jet and a novel frequency-spatial-domain elaboration procedure is proposed. The results show that the power supply ripple and the test chamber static pressure are the main driving parameters of the plasma jet unsteadiness. The thermodynamic state of the plasma flow is characterized using the steady Optical Emission Spectroscopy technique. Moreover, the implications of the plasma jet unsteadiness on the interpretation of the Optical Emission Spectroscopy results are discussed. The wall heat flux and the dynamic pressure are measured using copper probes, and the results are post-processed by means of a boundary layer code to rebuild the free-stream temperature. Finally, emission spectroscopy and intrusive measurement results at low static pressure are compared, and combined for the determination of the catalytic efficiency of the copper sensor's surface, used to measure the cold wall heat flux.

Publication year:2014

Keywords:Aerothermodynamics/Thermal Protection, nonintrusive diagnostics, Research facilities and instrumentation