Solid-State Microengines for Efficient and High-Endurance Performance

Abstract

Small unmanned aerial vehicles (< 1 kg) and locomotive robots offer an immense range of potential applications. However, they are currently held back because of their reliance on heavy lithium polymer batteries. This project investigates a novel approach to building a lightweight and efficient power supply. With the ultimate goal of creating an integrated ultra lightweight, powerful engine, the focus was designing and fabricating a microcombustor for optimal heat transfer between a combustion flame and thermoelectric energy converters. Multiple iterations of microcombustors were built with novel orifice designs. Using advanced deep reactive ion etching and yttrium aluminum garnet lasers, orifices with diameters ranging between 20-40 microns were fabricated, tested, and ultimately demonstrated feasibility. In order to effectively stabilize the flames and achieve efficient heat spreading without temperature loss in the substrate of the energy converters, different approaches were explored. A unique solution was found with Ni, Pt, and stainless-steel foams, which allowed for super adiabatic combustion by recirculating the heat through the foam medium. In addition, arrays of stable butane flames with radii under 1 mm were sustained by constructing 3 g aluminum combustors with either 2x2, 3x3, or 5x5 orifices. This thesis demonstrates how optimal coupling of lightweight microcombustors with advanced lightweight, solid-state heat-to-electricity energy converters is feasible in order for power generators to achieve higher specific energy metrics than competing technologies.