Practical aspects of fundamental research in thermionic conversion. Progress report, July 1, 1972--August 31, 1973

Rasor, N. S.; Britt, E. J.

doi:10.2172/4330142

Cited by 1 publication

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“…The presence of an ion approaching the surface can further lower the potential barrier for electrons, as shown in figure 1(b) and this effect is called the ion-induced Schottky enhancement. Ions can also transfer heat from the plasma to the surface directly, but their contribution to the heat balance is negligible compared to thermionic emission cooling in a thermal plasma [26]. If the surface is metal, the electrons inside the metal lattice can interact with the plasma electrons, which can also affect emission characteristics.…”

Section: Near Surface Phenomena Affecting Electron Transpiration Coolingmentioning

confidence: 99%

“…Many experimental studies exist to quantify the effect of cesium adsorption on tungsten emission properties with application considerations for thermionic devices and photocathodes [26,29,30]. This data cannot be used directly for ETC since hypersonic flight is associated with much higher pressures and surface temperatures.…”

Section: Effect Of Cesium Adsorption On Emitter Surface Latticementioning

confidence: 99%

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Cesium seeding for effective electron transpiration cooling in hypersonic flows

Sahu

Tropina

Andrienko

et al. 2022

Plasma Sources Sci. Technol.

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The concept of electron transpiration cooling (ETC) uses thermionic emission of electrons from a low work function material to cool surfaces in hypersonic ﬂight. A theoretical estimate of the emission current is given by the Richardson-Dushman equation. In hypersonic ﬂights, the emission current can deviate from this estimate as the ambient air is partially ionized and a plasma sheath forms near the surface. Depending on the sheath structure, the emission current can be enhanced by the Schottky eﬀect, or could be reduced by the space charge eﬀects. In this study, we present a theoretical analysis of electron transpiration cooling of the leading-edge surface of a hypersonic vehicle, considering the transpiration of liquid cesium through a porous tungsten material. A part of the transpired cesium is adsorbed on the surface, which lowers the emitter work function, while the rest is evaporated due to high surface temperatures. Both the eﬀects provide substantial cooling. The evaporated cesium is ionized in the ambient air, which alters the plasma conductivity and reduces space charge eﬀects. The eﬀect of individual ﬁelds of ionized species near the surface is found to be negligible. Cesium transpiration is found to eliminate the requirement for an applied surface bias and enable stable operation at surface temperatures below 2000 K.

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Section: Near Surface Phenomena Affecting Electron Transpiration Coolingmentioning

confidence: 99%

Section: Effect Of Cesium Adsorption On Emitter Surface Latticementioning

confidence: 99%