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Improving Power Density of Free-Piston Stirling EnginesAnalyses and experiments demonstrate the potential benefits of optimizing piston and displacer motion in a free-piston Stirling Engine. Isothermal analysis shows the theoretical limits of power density improvement due to ideal motion in ideal Stirling engines. More realistic models based on nodal analysis show that ideal piston and displacer waveforms are not optimal, often producing less power than engines that use sinusoidal piston and displacer motion. Constrained optimization using nodal analysis predicts that Stirling engine power density can be increased by as much as 58 percent using optimized higher harmonic piston and displacer motion. An experiment is conducted in which an engine designed for sinusoidal motion is forced to operate with both second and third harmonics, resulting in a piston power increase of as much as 14 percent. Analytical predictions are compared to experimental data and show close agreement with indirect thermodynamic power calculations, but poor agreement with direct electrical power measurements.
Document ID
20160014881
Acquisition Source
Glenn Research Center
Document Type
Technical Memorandum (TM)
Authors
Briggs, Maxwell H. (NASA Glenn Research Center Cleveland, OH United States)
Prahl, Joseph M. (Case Western Reserve Univ. Cleveland, OH, United States)
Loparo, Kenneth A. (Case Western Reserve Univ. Cleveland, OH, United States)
Date Acquired
December 29, 2016
Publication Date
December 1, 2016
Subject Category
Engineering (General)
Report/Patent Number
GRC-E-DAA-TN34746
AIAA Paper 2016-5016
E-19291
NASA/TM-2016-219383
Meeting Information
Meeting: International Energy Conversions Engineering Conference (IECEC)
Location: Salt Lake City, UT
Country: United States
Start Date: July 25, 2016
End Date: July 27, 2016
Sponsors: American Inst. of Aeronautics and Astronautics
Funding Number(s)
WBS: WBS 887359.04.01.04.03
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
aerospace engineering
cogeneration
Stirling engines
heat engines power generation
power generation control
thermodynamics
space technology

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