Date of Award

2016

Degree Type

Thesis

Degree Name

Master of Science in Mechanical Engineering

Department

Washkewicz College of Engineering

Subject Headings

Mechanical Engineering

Abstract

This thesis involves the fusion of two technologies, Stirling engines and additive
manufacturing. The project began by building a Stirling engine primarily out of 3D printed parts. Methods to measure the power output were designed and built with a combination of 3D printed and off the shelf parts. The Stirling engine was tested to see if there was a correlation to analysis results, and a regenerator was installed to determine the effect on performance for this relatively low temperature engine. Finally, variations in test operation and the use of heat sinks were used to find a combination that will allow the unit to run more reliably.
One challenge of the 3D printed parts was the durability when subjected to heat and assembly loads, especially over multiple rebuilds. However, the convenience of 3D
printing made it possible to print replacement parts easily. New designs and assemblies were also created as a part of the effort to develop a power measurement system.
Power output was measured and corresponded to analysis predictions. Testing was conducted with a hot plate temperature of 349K (168 F) and a cold plate temperature of 308K (94 F), which corresponds to a Temperature Ratio of 1.13. Rate of rotation was 150 RPM, or 2.5 Hz. The net power output was measured to be 3.1mW. Adding that to the losses attributed to engine friction resulted in a gross power output of 17mW, which was close to the analysis prediction of 15mW. Regenerator testing showed that using a regenerator, on average, doubled the speed of rotation at the same temperature ratio. However, the regenerator was detrimental to long term operation because without active cooling, the cold plate was unable to dissipate the heat efficiently enough. Increasing the cold side heat transfer to ambient would be essential in increasing reliability. The addition of heatsinks to the cold side was tested to determine the effectiveness, with positive results. The heatsinks that were used in testing were also analyzed, and it was determined that the spacing was too narrow for optimum performance. For future designs, custom heatsinks could be used that maximize the natural convection of the cold side, or a method developed to provide active cooling.

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