An involute-foil regenerator was designed, microfabricated, and tested in an oscillating-flow test rig. The concept consists of stacked involute-foil nickel disks (see figure) microfabricated via a lithographic process. Test results yielded a performance of about twice that of the 90-percent random-fiber currently used in small Stirling converters.

Micrographs of Regenerator Disks are shown during the final steps of fabrication: (a) micrograph of features with remaining PMMA removed and (b) picture of nickel ribs after removal from substrate.
The segmented nature of the involute-foil in both the axial and radial directions increases the strength of the structure relative to wrapped foils. In addition, relative to random-fiber regenerators, the involute-foil has a reduced pressure drop, and is expected to be less susceptible to the release of metal fragments into the working space, thus increasing reliability. The prototype nickel involute-foil regenerator was adequate for testing in an engine with a 650 °C hot-end temperature. This is lower than that required by larger engines, and high-temperature alloys are not suited for the lithographic microfabrication approach.

This work was done by Mounir Ibrahim and Daniel Danila of Cleveland State University; Terrence Simon, Susan Mantell, and Liyong Sun of the University of Minnesota; David Gedeon of Gedeon Associates; Songgang Qiu of Infinia Corp.; Gary Wood of Sunpower Inc.; and Kevin Kelly and Jeffrey McLean of International Mezzo Technologies for Glenn Research Center. For more information, download the Technical Support Package (free white paper) at under the Manufacturing & Prototyping category.

Inquiries concerning rights for the commercial use of this invention should be addressed to

NASA Glenn Research Center
Innovative Partnerships Office
Attn: Steve Fedor
Mail Stop 4–8
21000 Brookpark Road
Ohio 44135.

Refer to LEW-18431-1.

NASA Tech Briefs Magazine

This article first appeared in the November, 2010 issue of NASA Tech Briefs Magazine.

Read more articles from this issue here.

Read more articles from the archives here.