The development of renewable energy green technologies continue to challenge the limits on conventional hardware such as engines, compressors, heat exchangers, and generators This paper presents the results of a mechanical design and analysis of an expansion engine to be used as a renewable energy Supercritical Carbon Dioxide (SCO2) low waste heat to energy conversion device. Included in this paper are the results of a detailed mechanical design, stress analysis, finite element analysis (FEA) results, manufacturing bill-of-materials and detailed design drawings of the expansion engine. The hand-calculation stress analysis provides an upper bound of the machine component stresses; 97.8 ksi for the piston writs pin, 26.6 ksi for the connecting rod, 96.4 for the combustion chamber bolts. Fatigue safety factors range from 1.20 to 4.95 for various parts of the expansion engine. The FEA results indicate that the hand-calculation stress analysis results are at least 25% conservative. Manufacturing costs are estimated to be $32K with 88% of the cost Computer Numerical Control (CNC), 89% sand casting, and 3% 3-d printing. Materials selection for the engine’s high temperature environment specifies AIS1 1020 for sand-casted parts, AISI 1045 cold drawn for the CNC fabricated parts. Kinematics analysis suggests that the primary load path will witness 1.8 g’s of rotary acceleration. Keywords: Machine design, stress analysis, manufacturing, materials, renewable energy
