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Author:Laitonen, Henri Matias
Title:Koelaitteen suunnittelu roottorin värähtelyn vaimentamiseen
The design of a test device for damping rotor vibration
Publication type:Master's thesis
Publication year:2006
Pages:72      Language:   fin
Department/School:Konetekniikan osasto
Main subject:Koneensuunnitteluoppi   (Kon-41)
Supervisor:Pietola, Matti
Instructor:Hautala, Pekka
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark TKK  6469   | Archive
Abstract (eng): Squeeze film damper is based on a squeeze effect of a lubricant, which is sealed to a narrow gap between two cylinder surfaces.
Because of lubricant qualities, stream velocity in the gap is rather slow, which gives extra damping and separates the two surfaces from one another.
Phenomenon is similar to sliding bearings, but the one thing that makes a difference between these two, is the fact that in SF-damper, both outer and inner ring is stationary in terms of rotational movement.

According to literature, SF-damper is generally designed through practice, because the lack of good and working theories.
So, first one had to decide some initial values, the base of the whole design.
In literature, SF-dampers are split into two categories, based on the ratio between dampers width (s) and diameter (d).
In this work, the damper is so called "narrow" damper, which means that its s/d ratio is under 0,25.

The tests were done in three stages: First totally rigid construction for reference, then damper with 0,1 mm radial clearance and last, same damper with same initial values, but with lower rotational frequency.
The displacement of the centre bearing housing was measured and results with different installations were compared.
It was obvious that in vertical direction, displacements were considerable lower with lower rotational frequencies, but in horizontal direction, displacements were even bigger than before.
The reasons, that might have had influence on these results, are discussed thoroughly in chapter 6: "Tulokset" According to these studies, the most significant result of this work was the construction of working and developable SF-damper, with which the tests and measurements could easily be redone in the future if necessary for further development.
Abstract (fin): Squeeze film -vaimennin (SF) perustuu kapeassa raossa olevan nestekalvon puristumiseen kahden lieriöpinnan välissä.
Nesteen ominaisuuksien takia virtaus ahtaassa raossa on hidasta, jolloin kalvon erottamat pinnat eivät pääse kosketukseen toistensa suhteen.
Vastaavanlainen ilmiö on tuttu liukulaakereista, erona kuitenkin on SF-vaimentimen ulko- ja sisäkehän liikkumattomuus.

Kirjallisuuden mukaan SF-vaimentimen suunnittelu ja kehittely on pitkälti kokeellista, olemassa olevien teorioiden ollessa puutteellisia.
Oli siis valittava jotkin alkuarvot, joiden pohjalta vaimenninkoelaitteen suunnittelu aloitettiin.
SF-vaimentimet jaotellaan kirjallisuudessa vaimenninpinnan leveyden (s) ja halkaisijan (d) suhteen mukaan.
Työssä rakennettu vaimenninkoelaite edustaa tyyppiä, jonka s/d -suhde on alle 0,25 eli se on niin sanotusti "kapea" vaimennin.

Koeajot suoritettiin kolmessa vaiheessa: Ensin referenssimittaukset ilman vaimennusta, seuraavaksi 0,1 mm radiaalisella öljykalvolla ja lopuksi samoilla vaimennusarvoilla, mutta pienemmillä roottorin kierrostaajuuksilla.
Tukilaakeripesän siirtymiä verrattiin testimittausten välillä ja todettiin että y-akselin suunnassa tukilaakeripesän siirtymät pienennivat alhaisilla kierrostaajuuksilla oleellisesti, mutta x-suuntaiset siirtymät jopa kasvoivat.
Syitä, jotka saattoivat vaikuttaa tulokseen, käsitellään erikseen kappaleessa 6: "Tulokset".

Merkittävimpänä tuloksena saatiin rakennettua näiden mittausten valossa toimiva ja kehityskelpoinen SF-vaimennin, jolla mittauksia voidaan tulevaisuudessa tarvittaessa toistaa ja näin kehittää vaimenninta edelleen.
ED:2006-02-21
INSSI record number: 30636
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