Mechanical and Thermal Design of a Combustion-Based Thermionic Micro Power Generator

This paper reports the mechanical and thermal design of a MEMS-fabricated micro power generator based on thermionic emission and catalytic combustion. Thermionic power generation results from electron emission from a hot emitter to a cold collector. Scaling analysis reveals that the miniaturization of a thermionic generator is favorable to output power density and efficiency, provided that excellent thermal isolation can be realized. However, there are stringent constrains on the thermal and mechanical properties of the micro device structure. Thermal and structural analyses have been performed and prototype structures have been designed and fabricated. SiO2 rings of thickness ~40–50μm surrounding the combustion chamber and emitter are used for thermal isolation. Excellent thermal behavior of the structures is shown both in finite element simulations and experiments. The simulations also show that the emitter bending under pressure and thermal stresses is less than 3μm.