Stress and Displacement Analysis of Microreactors during Thermal and Vacuum Loading

Report No. ARL-TR-8121
Authors: William Allmon and C Mike Waits
Date/Pages: September 2017; 26 pages
Abstract: Compact power sources with high energy and power densities are critical for many military applications. These applications span from personal or squad-level power sources for long-duration missions without resupply to unmanned air vehicles requiring only a few hours of running time. In the 10–100 W+ power range, battery technology is the best solution currently available, but higher-energy dense technologies are needed to augment batteries and extend the available energy density well beyond state-of-the-art battery technology. One way to approach this is to take advantage of the large energy content of hydrocarbons. Conversion efficiencies of only a few percent can provide comparable energy density to battery technology. One technology being pursued by the US Army Research Laboratory is combustion-based thermophotovoltaic power sources. Combustion can be used to convert fuel to heat a surface to temperatures above 500 °C. An emitter could be vacuum brazed to the heated surface. This assembly method creates stresses due to difference in the coefficient of thermal expansion of the materials. Additional stresses are introduced, since the exterior of the assembly operates at vacuum while the interior is at ambient pressure. This report provides an analysis of 2 approaches to manage the stresses in the assembly.
Distribution: Approved for public release
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Last Update / Reviewed: September 1, 2017