TY - GEN
T1 - Modeling of electron transpiration cooling for hypersonic vehicles
AU - Hanquist, Kyle M.
AU - Hara, Kentaro
AU - Boyd, Iain D.
N1 - Publisher Copyright:
© 2016, American Institute of Aeronautics and Astronautics Inc, AIAA. All right reserved.
PY - 2016
Y1 - 2016
N2 - Electron transpiration cooling (ETC) is a recently proposed approach to manage the high heating loads experienced at the sharp leading edges of hypersonic vehicles. Computational fluid dynamics can be used to investigate the feasibility of ETC in a hypersonic environment. A modeling approach is presented for ETC, which includes devloping the boundary conditions for electron emission from the surface, accounting for the electric field and space-charge limit effects within the near-wall plasma sheath. Two different analytical models for space-charge limited emission are discussed. The first model assumes that the electrons are emitted cold from the surface while in the second approach the emitted electrons have a finite temperature. The theory shows that emitted electrons with a finite temperature, referred to as warm emission in the present paper, can reach higher levels of emission. This is important because the benefit of ETC, mainly reduction in the surface temperature, is directly correlated to the level of electron emission from the surface. The space-charge limit models are assessed using 1D direct-kinetic plasma sheath simulations. The simulations agree well with the space-charge limit theory proposed by Takamura et al. for emitted electrons with a finite temperature. Both models are implemented into a CFD code, LeMANS, and run for a test case typical of a leading edge radius in a hypersonic flight environment. The CFD results show finite temperature theory results in a larger reduction in wall temperature because more electron emission is allowed for than the cold emission theory. However, even with the electrons being emitted with a finite temperature, the emission still reaches space-charge limits for the test case considered, which can limit the benefits of ETC.
AB - Electron transpiration cooling (ETC) is a recently proposed approach to manage the high heating loads experienced at the sharp leading edges of hypersonic vehicles. Computational fluid dynamics can be used to investigate the feasibility of ETC in a hypersonic environment. A modeling approach is presented for ETC, which includes devloping the boundary conditions for electron emission from the surface, accounting for the electric field and space-charge limit effects within the near-wall plasma sheath. Two different analytical models for space-charge limited emission are discussed. The first model assumes that the electrons are emitted cold from the surface while in the second approach the emitted electrons have a finite temperature. The theory shows that emitted electrons with a finite temperature, referred to as warm emission in the present paper, can reach higher levels of emission. This is important because the benefit of ETC, mainly reduction in the surface temperature, is directly correlated to the level of electron emission from the surface. The space-charge limit models are assessed using 1D direct-kinetic plasma sheath simulations. The simulations agree well with the space-charge limit theory proposed by Takamura et al. for emitted electrons with a finite temperature. Both models are implemented into a CFD code, LeMANS, and run for a test case typical of a leading edge radius in a hypersonic flight environment. The CFD results show finite temperature theory results in a larger reduction in wall temperature because more electron emission is allowed for than the cold emission theory. However, even with the electrons being emitted with a finite temperature, the emission still reaches space-charge limits for the test case considered, which can limit the benefits of ETC.
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U2 - 10.2514/6.2016-4433
DO - 10.2514/6.2016-4433
M3 - Conference contribution
AN - SCOPUS:85088203347
SN - 9781624104350
T3 - 46th AIAA Thermophysics Conference
BT - 46th AIAA Thermophysics Conference
PB - American Institute of Aeronautics and Astronautics Inc, AIAA
T2 - 46th AIAA Thermophysics Conference, 2016
Y2 - 13 June 2016 through 17 June 2016
ER -