- Friday, 01 August 2014
The seal can be sized to any application while maintaining its important features.
John H. Glenn Research Center, Cleveland, Ohio
This seal features dual sealing capabilities: a face seal and an axial seal. The name swan seal is derived from its cross section, which resembles a swan. Most injector designs require fuel to be delivered from an inlet fitting, through a feed arm, to the injector tip. Temperature variation from the inlet to the tip, from the cool fuel to hot combustion air, and from startup to full power, often poses a challenge due to thermal growth. One of the most challenging areas is accommodating the growth differential between a hot feed arm and a cool fuel delivery tube, which is exacerbated by the relatively long distance. Several methods have been used to allow for this including coiling the fuel tube, utilizing an O-ring sliding seal, metal C-seals, or incorporating stretchable bellows. Some of the drawbacks of these methods include limited space, poor durability at high temperatures, serviceability, long lead times, and cost. The swan seal presents a compact, high-temperature, replaceable, low-cost option for this and other applications where a sliding axial seal is required.
The seal was developed to fill the need for a seal that could be manufactured in a short lead time and be capable of withstanding high temperatures and pressures, as well as accommodate thermal growth. Metal C-seals are commonly used in similar applications. However, designers are usually faced with long lead times and high front end costs when considering C-seals from industry suppliers. Swan seals can be custom designed and manufactured in a typical machine shop. The dual seal features, as well as the redundancy built into the seal, may outperform currently available commodities such as C-seals, making it attractive to companies that specialize in sealing solutions.
This device is capable of sealing in both the diametrical and face sealing portions of a diametrical shaft, with the capability of allowing the shaft to move in relationship to the item that it is sealed to. In the first application, it was used to seal a tube exiting from a rig test spool section. The part provided sealing between the two items while allowing the tube to move in relationship to the spool section with the movement caused by thermal growth. This type of sealing arrangement would typically be accomplished using a C-seal. However, a C-seal only seals either diametrically or on two faces, whereas the swan seal provides sealing between a face and a diameter.
The seal’s application is potentially very broad, and would have relevance in many products other than that for which it was conceived. It could be a high-volume product, as a new seal should be installed if parts are disassembled. Another advantage to the swan seal is that it inherently provides backup sealing mechanisms.
This work was done by John Earl Short, Gregory Zink, and Spencer Pack of Goodrich Engine Components for Glenn Research Center.
Inquiries concerning rights for the commercial use of this invention should be addressed to NASA Glenn Research Center, Innovative Partnerships Office, Attn: Steven Fedor, Mail Stop 4–8, 21000 Brookpark Road, Cleveland, Ohio 44135. Refer to LEW-19094-1.
This Brief includes a Technical Support Package (TSP).
Swan Seal (reference LEW-19094-1) is currently available for download from the TSP library.
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