Numerical Model of Thermionic- and Photo- emission Electron Heat Spreading

TL;DR

This paper develops a numerical model to analyze thermionic and photoemission electron heat spreading, revealing how geometry and temperature gradients influence cooling efficiency for hypersonic leading edges.

Contribution

It introduces a novel numerical simulation approach for combined thermionic and photoemission cooling, considering various geometries and temperature gradients.

Findings

Heat spreading is significant over length scales comparable to electron trajectories.

Smaller leading edge radii result in larger surface area affected by heat spreading.

Electron trajectories depend on potential space and temperature gradient configurations.

Abstract

Thermionic emission has been exploited to give rise to the theory of thermionic cooling also known as electron transpiration cooling, which can potentially serve as a powerful and engineerable cooling mode for hypersonic leading edges that can reach temperatures exceeding 2000 {\deg}C. However, the contribution to this cooling mode by photoexcited electrons remains relatively unexplored. Here, we present a numerical model of thermionic emission and photoemission driven cooling and heat spreading, examining the trajectories of electrons emitted based on a random energy model within a prescribed potential space. By simulating surfaces with two different temperature gradients, and imposing potential spaces derived for Cartesian, cylindrical, and spherical coordinate systems, we demonstrate that heat spreading can be significant for temperature gradients on a length scale comparable to the electron spreading distance. Additionally, by testing two different leading edge radii, we find that heat spreading affects a larger percentage of surface area for a smaller leading edge radius.