Assessing the performance of a microfabricated regenerator for Stirling space-power convertor

In this paper we provide a summary of accomplishments on phase I, and the early part of phase II, of our NASA regenerator microfabrication contract. We developed a microscale regenerator design based on state of the art analytical and computational tools. For this design we projected 6-9% efficiency improvement for the microfabricated regenerator. We were able to identify a manufacturing process and selected a vendor. This vendor completed EDM tools for fabricating the regenerator. The tool met specifications and they are ready to begin producing regenerators. We designed a Large Scale Mock-Up (LSMU) and began its fabrication. CFD modeling for fluid flow and heat transfer (both steady and oscillatory flow conditions) is proceeding for different geometries to assess: the effects of surface roughness, geometries such as a lenticular array, aligned parallel plates (equally and non-equally spaced), staggered parallel plates (equally and non-equally spaced), 3-D involute, and the LSMU model. Also, we examined adapting a test engine to incorporate the new microfabricated regenerator. The Sage code was used in this modeling exercise to compare computed results between the baseline random-fiber regenerator and the microfabricated regenerator. Sage modeled this new regenerator (the involute-element) as a simple foil-type regenerator. 3-D CFD analysis showed good agreement for fluid flow and heat transfer between parallel plates (foil-type), and involute geometries. Sage modeling showed an improved efficiency of 6-9%, the base line efficiency is 42.2% while that of the modified test engine with the new regenerator and 6% improvement is 44.8%. The Sage modeling indicates that even better efficiencies can be achieved if a space-power converter would be designed from the ground up to employ a microfabricated regenerator. In addition to the improved efficiency our structural analysis for the new microfabricated regenerator indicates a higher reliability and an increased potential for long-life high performance compared to the random-fiber regenerator.