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Effects of Compression, Staging, and Braid Angle on Braided Rope Seal PerformanceFuture turbine engines and industrial systems will be operating at increased temperatures to achieve more demanding efficiency and performance goals. In the highest temperature sections of the engine new material systems such as ceramics and intermetallics are being considered to withstand the harsh thermal environment. Components constructed of these low expansion-rate materials experience thermal strains and a resulting reduction of life when rigidly attached to high expansion-rate, superalloy support structures. Seals are being designed to both seal and to serve as compliant mounts allowing for relative thermal growths between high temperature but brittle primary structures and the surrounding support structures. Previous seal research yielded several braided rope seal designs which demonstrated the ability to both seal and serve as a compliant mount. The hybrid seal was constructed of an all-ceramic (alumina-silica) core overbraided with a superalloy wire sheath (cobalt based superalloy). The all ceramic seal was constructed of an all-ceramic (alumina-silica) core overbraided with multiple ceramic (alumina-silica) sheath layers. Program goals for braided rope seals are to improve flow resistance and/or seal resilience. To that end, the current report studies the test results of: baseline and modified hybrid seals; two stage hybrid and two stage all-ceramic seal configurations; and single stage hybrid and single stage all-ceramic seal configurations for a range of seal crush conditions. Hybrid seal modifications include increasing the sheath braid angle and core coverage. For the same percent seal cross-sectional crush, results show that increasing the hybrid seal braid angle increased seal stiffness and seal unit load, resulting in flows approximately one third of the baseline hybrid seal flows. For both hybrid and all-ceramic seals, two stage seal configurations significantly outperformed single stage configurations. Two stage seal flows were at least 30% less than the single stage seal flows for the same seal crush. Furthermore, test results of single stage seals indicate that for both all-ceramic and hybrid seals, a specific seal crush condition exists at which minimum flows are achieved (i.e. increasing seal crush beyond a certain point does not result in better flow performance). Flow results are presented for a range of pressures and temperatures from ambient to 1300 F, before and after scrubbing. Compression tests results show that for both all-ceramic and hybrid seals, seal preload and stiffness increase with seal crush, but residual seal interference remains constant.
Document ID
19970026182
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Steinetz, Bruce M. (NASA Lewis Research Center Cleveland, OH United States)
Adams, Michael L. (Modern Technologies Corp. Middleburg Heights, OH United States)
Date Acquired
September 6, 2013
Publication Date
July 1, 1997
Subject Category
Mechanical Engineering
Report/Patent Number
AIAA Paper 97-2872
NASA-TM-107504
E-10806
NAS 1.15:107504
Meeting Information
Meeting: Propulsion
Location: Seattle, WA
Country: United States
Start Date: July 6, 1997
End Date: July 9, 1997
Sponsors: Society of Automotive Engineers, Inc., American Society for Electrical Engineers, American Inst. of Aeronautics and Astronautics, American Society of Mechanical Engineers
Accession Number
97N25513
Funding Number(s)
PROJECT: RTOP 505-23-2L
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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