Design Optimization of Flexure Springs for Free-Piston Stirling Engines and Experimental Evaluations with Fatigue Testing

Chang-Whan Lee, Dong-Jun Kim, Sung-Kwon Kim and Kyuho Sim
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Chang-Whan Lee: Department of Mechanical System Design Engineering, Seoul National University of Science and Technology, Seoul 01811, Korea
Dong-Jun Kim: Department of Mechanical System Design Engineering, Seoul National University of Science and Technology, Seoul 01811, Korea
Sung-Kwon Kim: Department of Mechanical System Design Engineering, Seoul National University of Science and Technology, Seoul 01811, Korea
Kyuho Sim: Department of Mechanical System Design Engineering, Seoul National University of Science and Technology, Seoul 01811, Korea

Energies, 2021, vol. 14, issue 16, 1-17

Abstract: The free-piston Stirling engine is a closed-cycle regenerative heat engine that converts heat energy into mechanical work, and requires a spring element for vibratory operations of the displacer and power pistons. In this study, the geometry of the flexural spring design was optimized through structural finite element analyses and fatigue test evaluations. First, we constructed a target design space considering the required natural frequency of the displacer spring assembly under the geometric constraints of total mass and module height. The design of experiments was employed to construct simulation cases for design factors such as the outer diameter, thickness, and number of spirals in the spring sheet. As a result, the optimized design values were obtained to satisfy the design requirements. We also fabricated a test spring specimen and conducted fatigue tests using a linear actuator system developed to have the same motion as the engine. The test results indicated that the optimized spiral spring had no fracture under operating conditions with the design piston amplitude, revealing the effectiveness of the design method.

Keywords: free-piston Stirling engine; thermal cycle; design optimization; fatigue testing; flexure spring (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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