Measuring high-enthalpy inductively coupled plasma flows via coherent via coherent anti-Stokes Raman scattering

Abstract

Measurements in high-enthalpy environments representative of hypersonic flows are challenging due to background radiation, chemical reactions, extreme temperatures, and potential thermal and chemical nonequilibrium. Coherent anti-Stokes Raman scattering (CARS) is a non-linear optical four-wave mixing process which can be used as a gas phase diagnostic with properties that make it particularly useful for this kind of challenging environment. I will give an overview of challenges and results performing temperature measurements in the range of 3000–7000 kelvin using CARS in the high-enthalpy flow of an inductively coupled plasma torch. CARS was also used to simultaneously measure temperature and the relative CO to N₂ concentration in the boundary layer of a graphite sample exposed to this high-enthalpy flow. The resulting data provides crucial insight into heat transfer and oxidative chemistry affecting the survivability of carbon-based ablative heat shields.

About the speaker

Dr. Dan Fries is an Assistant Professor in the Mechanical and Aerospace Engineering Department at the University of Kentucky leading the CoRe Flow Lab (Complex Reacting Flow Lab). His research utilizes optical and laser spectroscopic measurement techniques for the experimental characterization of fluid mechanical, chemical, and interface processes in high-enthalpy and high-speed flows. To perform this research, the CoRe Flow Lab utilizes microwave and inductive plasma sources for the generation of high-enthalpy flows and works on the inversion of comprehensive measurement models for parameter inference and uncertainty quantification. The lab collaborates closely with researchers at Sandia National Labs and computational researchers. Applications of the research include hypersonic flight, atmospheric reentry, chemical and electrical propulsion systems, and the reduction of the environmental footprint of these technologies.