Investigation of the influence mechanism of hypersonic flow field environment on thermionic emission efficiency.

• A dual-sheath thermionic emission model used for hypersonic flow is established. • The main factors influencing the efficiency of thermionic emission is identified. • The neutralization effect on the thermionic emission efficiency is explained. • Thermionic emission efficiency reach 80 % when plasma ion density is 5 × 1020 m−3. Electron Transpiration Cooling (ETC) is a novel thermal management method that utilizes thermionic emission to cool the leading edge surface of a hypersonic vehicle. Establishing a thermionic emission model that accounts for the hypersonic flow field environment is imperative for accurately predicting the thermal protection efficiency of ETC. A thermionic emission dual-sheath model was established, considering the impact of hypersonic non-equilibrium flow field particle parameters on thermal electron emission. The virtual cathode threshold was obtained through numerical analysis, considering the influence of particles parameters and surface thermoelectric material parameters in a non-equilibrium flow field. Distribution of sheath potential and particle number density in plasma sheath region were performed at a range of conditions. Thermionic emission efficiency approached 80 % as the plasma ion density was 5 × 20 m−3 and the work function was 2 eV. The results showed that plasma ions have different degrees of neutralization effect on thermal emission electrons depending on the flow field and surface material characteristics, ultimately causing varying surface thermionic emission efficiency. [ABSTRACT FROM AUTHOR]