High energy density entrainment-based catalytic micro-combustor for portable devices in extreme environmental conditions

Abstract

The increasing demand for low-cost, high energy density heat sources has motivated the development of compact and lightweight combustion-based devices. In this work, we first optimized the catalytic bed segmentation scheme to enhance fuel management in a mesoscale parallel-plate combustor. After contextualizing the driving parameters for combustion efficiency, we developed an energy-dense (≈236 MW/m³) entrainment-based catalytic micro-combustor for heating portable systems. The multichannel micro-combustor (coated with Pt/Al₂O₃ catalyst) leverages a copper-nichrome wire to enable quick and localized ohmic preheating durations (2-3 mins). Furthermore, we demonstrated low ignition temperature (108-125°C), which facilitates low energy consumption (~1948 J). In addition, an optimal fuel flow rate (3.09×10⁻⁸ m³/s) was determined via FEM simulations and experiments to enable fuel savings (high fuel conversion) while achieving high heat fluxes by analyzing the reaction kinetics and species transport behavior in the microchannels. Additional FEM studies were performed to optimize the heat transfer between the high thermal mass and combustor at the insulating mica sheet stack interface. Afterwards, through independent testing, we established the micro-combustor’s ability to maintain long-term autothermal combustion at a high saturation wall temperature (585°C), which was attained at short timescales to enable fast heating/cooling cyclability. The successful cyclic heating demonstration of large thermal mass additions (at least 41 times the micro-combustor’s mass), coupled with the combustor’s high energy density, shows promise for device-level implementation for a range of commercial, defense, and energy conversion applications. Finally, a combustor array was assembled and tested in an atmospheric water extractor (AWE) device in harsh environmental conditions, at temperatures ranging from 1.7°C to 43.3°C.