NASA LogoNTRSNTRS - NASA Technical Reports ServerSearchmore_vertCollectionsAboutNewsHelpLogin Back to ResultsFree-Piston Stirling Power Conversion Unit for Fission Power System, Phase II Final ReportIn Phase II, the manufacture and testing of two 6-kW(sub e)Stirling engines was completed. The engines were delivered in an opposed 12-kW(sub e) arrangement with a common expansion space heater head. As described in the Phase I report, the engines were designed to be sealed both hermetically and with a bolted O-ring seal. The completed Phase II convertor is in the bolted configuration to allow future disassembly. By the end of Phase II, the convertor had passed all of the final testing requirements in preparation for delivery to the NASA Glenn Research Center. The electronic controller also was fabricated and tested during Phase II. The controller sets both piston amplitudes and maintains the phasing between them. It also sets the operating frequency of the machine. Details of the controller are described in the Phase I final report. Fabrication of the direct-current to direct-current (DC-DC) output stage, which would have stepped down the main controller output voltage from ~700 to 120 V(sub DC), was omitted from this phase of the project for budgetary reasons. However, the main controller was successfully built, tested with the engines, and delivered. We experienced very few development issues with this high-power controller. The project extended significantly longer than originally planned because of yearly funding delays. The team also experienced several hardware difficulties along the development path. Most of these were related to the different thermal expansions of adjacent parts constructed of different materials. This issue was made worse by the large size of the machine. Thermal expansion problems also caused difficulties in the brazing of the opposed stainless steel sodium-potassium (NaK) heater head. Despite repeated attempts Sunpower was not able to successfully braze the opposed head under this project. Near the end of the project, Glenn fabricated an opposed Inconel NaK head, which was installed prior to delivery for testing at Glenn. Engine development prior to this was performed using both single- and dual-opposed (common expansion space) Inconel heads with clamp-on electric heaters.Document ID20160010605Acquisition SourceGlenn Research CenterDocument TypeContractor Report (CR)AuthorsWood, J. Gary*(SunPower, Inc. Athens, OH, United States)*Stanley, John*(SunPower, Inc. Athens, OH, United States)*Date AcquiredAugust 29, 2016Publication DateAugust 1, 2016Subject CategorySpacecraft Propulsion And PowerReport/Patent NumberGRC-E-DAA-TN29210E-19217NASA/CR-2016-219088Funding Number(s)WBS: WBS 887359.02.03.06.01CONTRACT_GRANT: NNC09CA23CDistribution LimitsPublicCopyrightPublic Use Permitted.KeywordsFree-piston Stirling Power Conversion UnitNaK heating circuitFission Surface PowerAvailable DownloadsNameType20160010605.pdfSTIcloud_downloadcontent_copyvisibilityRelated RecordsThere are no records associated with this record.visibility_offNo Preview Available
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