Comparisons of Computations with Experiments for Electron Transpiration Cooling at High Enthalpies

Abstract

A modeling approach for electron transpiration cooling of high enthalpy flight is compared to a set of experiments performed in a plasma arc tunnel for nitrogen and argon. The comparisons include nitrogen and argon flow at high enthalpies, 12,000 btu/lb and 5,000 btu/lb respectively, with a Mach number of 2.5 to 3. Converting the provided enthalpies and Mach numbers to freestream temperatures and velocities is discussed. The numerical approach is described including implementation of a thermionic emission boundary condition. Also described is the implementation of a finite-rate chemistry model for argon ionization. Different emissive materials are also investigated including graphite and tungsten. The comparisons include two different geometries with different leading edge radii. The numerical results produce a wide range of emitted current due to the uncertainties in freestream conditions and emissive material properties, but still agree well with the experiments. Future work recommendations are provided that may improve the physical accuracy of the modeling capabilities used in the comparisons.

Limits for Thermionic Emission from Leading Edges of Hypersonic Vehicles

“…The modeling approach for ETC was recently compared against a set of experiments and agreed well. 6 This paper focuses on the plasma physics occurring near the emissive surface. A plasma sheath will form near the vehicle surface, which is a region of non-neutral potential.…”