Editing Labyrinth seal

{{Short description|Mechanical seal consisting of tightly interlinked parts to prevent leakage}}
[[Image:labyrinth-seal.png|right|thumb|250px|A simple labyrinth seal]]
[[File:Labyrinthdichtung01.jpg|right|thumb|250px|A labyrinth seal on a steam turbine shaft]]

A '''labyrinth seal''' is a type of [[seal (mechanical)|mechanical seal]] that provides a tortuous path to help prevent leakage. An example of such a seal is sometimes found within an [[axle]]'s [[bearing (mechanical)|bearing]] to help prevent the leakage of the oil [[lubricating]] the bearing. 

A labyrinth seal may be composed of many [[groove (machining)|groove]]s that press tightly inside another axle, or inside a hole, so that the fluid has to pass through a long and difficult path to escape. Sometimes [[screw thread]]s exist on the outer and inner portion. These interlock, to produce the long characteristic path which slows leakage. For labyrinth seals on a rotating shaft, a very small clearance must exist between the tips of the labyrinth threads and the running surface. The "teeth" of the labyrinth seal may be on the rotating shaft (teeth on rotor - TOR) or on the stator (TOS), or both, in an interlocking configuration.<ref>[https://oaktrust.library.tamu.edu/bitstream/handle/1969.1/163245/t33-14.pdf Thermoplastic Labyrinth Seals for Centrifugal Compressors; ''Proceedings of the Thirty-Third Turbomachinery Symposium'']</ref>

Labyrinth seals on rotating shafts provide non-contact sealing action by controlling the passage of fluid through a variety of chambers by centrifugal motion, as well as by the formation of controlled fluid vortices. At higher speeds, centrifugal motion forces the liquid towards the outside and therefore away from any passages. Similarly, if the labyrinth chambers are correctly designed, any liquid that has escaped the main chamber becomes entrapped in a labyrinth chamber, where it is forced into a vortex-like motion. This acts to prevent its escape, and also acts to repel any other fluid. Because these labyrinth seals are non-contact, they do not wear out.

Many [[gas turbine]] engines, having high rotational speeds, use labyrinth seals due to their lack of friction and long life. Because liquid-filled labyrinth seals still generate heat due to the viscosity of the seal oil, and because seal oil can contaminate the process fluids, modern high-performance gas turbines use [[dry gas seal]]s which use spring-loaded rings with an inert gas in between the faces of the rings to provide the seal. This creates even lower friction and provides a liquid-free seal.<ref name="BlochAndSoares">{{cite book|last1=Bloch|first1=Heinz P.|last2=Soares|first2=Claire|title=Turboexpanders and process applications|date=2001|publisher=Gulf Professional Pub.|location=Boston|isbn=9780884155096|page=348|url=https://books.google.com/books?id=Z-RY1Emx4JwC&pg=PA348|accessdate=25 December 2016}}</ref> However, such engines often have detectable oil leakage into the compression chamber.<ref name="SealsAndSealing">{{cite book|last1=Flitney|first1=Robert|title=Seals and Sealing Handbook, 6th Edition|date=2014|publisher=Butterworth-Heinemann|isbn=978-0-08-099416-1}}</ref> Indeed, many gas turbine engine seals leak by design.<ref name="AircraftCabinAir">{{cite speech|last=Scholz|first=Dieter|title=Aircraft Cabin Air and Engine Oil - An Engineering View|event=International Aircraft Cabin Air Conference 2017|date=September 19, 2017|location=[[Imperial College London]]|url=http://www.fzt.haw-hamburg.de/pers/Scholz/Aero/AERO_PRE_GCAQE2017_CabinAirAndEngineOil_17-09-19.pdf}}</ref>

Labyrinth seals are also found on pistons, which use them to store oil and seal against high pressure during compression and power [[stroke (engine)|stroke]]s, as well as on non-rotating shafts. In these applications, it is the long and difficult path and the formation of controlled fluid vortices plus some limited contact-sealing action that creates the seal.

==See also==
* [[Tesla valve]]

==References==
<references />

[[Category:Seals (mechanical)]]