Expansion turbines seals

Gas expansion turbines may embody different designs depending on the proeess media and assoeiated systems. Speeial requirements may pertain to duties sueh as sealing off toxie, flaimuable, eaustie, eoiTosive, erosive, and high-temperature media. These requirements may lead to sealing geometries tliat are eommon to mrbines and turboeompressors. 

Demands for improved efficiency in aircraft gas turbines led to the use of a family of age hardenable, controlled expansion superaHoys for engine seals and casings. INCOLOY aHoys 903 [61107-16-2] (UNS N19903), 907 [107652-23-3] (UNS N19907), and 909 evolved from a continuing effort to improve the environmental resistance of this Cr-free, Fe—Ni—Co based system. 

In large gas turbines labyrinth seals are used in statie as well as dynamie applieations. The essentially statie funetion oeeurs where the easing parts must remain unjoined to allow for differenees in thermal expansion. At this junetion loeation, the labyrinth minimizes leakage. Dynamie labyrinth applieations for both turbines and eompressors are interstage seals, shroud seals, balanee pistons, and end seals. 

Porous aluminum titanate DMO has both a low thermal expansion coefficient (nearly zero at least up to 600°C) and a low thermal conductivity, suggesting possible applications in thermal barriers and abradable seals for turbine rotor shrouds [116] and automobile exhaust port liners and gas desulfurization nozzles [117]. Other possible thermal applications of silicon carbide reinforced DMO include heat exchangers [117] and flaps and seals in the afterburners of jet engines [119]. In addition, SiC particulate-reinforced DMO could serve as a lossy insert for high powered microwave tubes, withstanding temperatures up to 1000°C in ultrahigh vacuum. 

The turbine exhaust E seal was replaced with a segmented cylindrical piston ring seal, which became typical of all other seals. The turbine vertical inlet face seal was replao with two horizontal segmented cylindrical piston ring seals between the turbocompressor and a new adapter. These seals, located above and below the hot duct, are the same type as the turbine exhaust seal. The tee-shaped adapter also interfaces to the hot duct with a segmented piston ring seal that replaces the hot duct bellows that was previously used to accommodate thermal expansion. 

The alloy should be considered for applications in which other current low-expansion superalloys are presently used, such as compressor and exhaust casings, seals, and other gas turbine engine components. 

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