Effect of rotor asymmetry and support stiffness on subcritical vibration

Risto Viitala

Effect of rotor asymmetry and support stiffness on subcritical vibration

Julkaisun otsikon käännös: Roottorin asymmetrian ja tuen jäykkyyden vaikutus alikriittiseen värähtelyyn

Risto Viitala

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Työssä tutkittiin roottorin taivutusjäykkyysvaihtelua (TJV) sekä roottorin tuennan vaikutusta sen dynaamiseen käyttäytymiseen. Tyypilliset roottoritestit eivät täysin estä TJV:n ja tuennan jäykkyyden aiheuttamia värähtelyongelmia käyttöolosuhteissa. Tämän takia TJV:sta ja tuennan jäykkyydestä johtuvat värähtelyongelmat tarvitsevat vielä syvällisempää tutkimusta, ja roottorit, jotka ovat taipuvaisia kyseisiin värähtelyongelmiin, kattavamman värähtelytestauksen ongelmien ratkaisemiseksi. Tutkimuksessa kehitettiin horisontaalista tuennan jäykkyyttä säätävä laite, joka integroitiin osaksi roottoritestipenkkiä. Tämä mahdollisti tuennan vaikutuksen tutkimisen roottorin dynaamiseen käyttäytymiseen. Laitetta voitiin käyttää myös havainnollistamaan roottorin käyttäytymistä erilaisissa käyttöolosuhteissa ja näin varmistamaan roottorin sujuva käyttöönotto. Laitteen jäykkyyttä voitiin portaattomasti säätää välillä 2–18 MN/m, mikä vaikutti roottorin horisontaalisiin ominaistaajuuksiin yli 50%. Lisäksi tutkittiin roottorin geometrian yhteyttä taivutusjäykkyysvaihteluun. Vakiopoikkileikkauksisia roottoreita tutkittiin analyyttisesti käyttäen erikseen yksittäisiä ympyrämäisyys komponentteja, komponenttipareja ja komponenttikombinaatioita. Poikittaissuuntaisen kuorman vaikutusta TJV:n aiheuttamaan herätteeseen tutkittiin kokeellisesti sekä simuloimalla, sekä ei-vakiopoikkileikkauksisten roottoreiden TJV:a simuloitiin. Kehitetty tuennanmuutoslaite pystyi laajalla alueella muuttaa roottorin tuennan jäykkyyttä. Jäykkyyden huomattiin vaikuttavan eritavoin joustavan testiroottorin ominaistaajuuksiin. Laite mahdollisti uudenlaisen roottoritestimenetelmän, missä roottorin toiminta erilaisissa käyttöolosuhteissa pystytään varmistamaan. Lisäksi laitetta voidaan hyödyntää roottorin dynaamisen käyttämisen optimoinnissa, kun sitä käytettään semiaktiivisena jäykkyyttä muuttavana toimilaitteena. Taivutusjäykkyysvaihtelututkimus pystyi erottamaan haitalliset TJV:a aiheuttavat roottorigeometriat; yksittäisten ympyrämäisyys komponenttien analyysi osoitti, että ainoastaan toinen komponentti (ovaalisuus) pystyi tuottamaan TJV:a kiinteissä roottoreissa, kun taas putkimaisissa roottoreissa, sitä tuotti myös ensimmäinen komponentti (epäkeskisyys). Jotkin komponenttiparit pystyivät tuottamaan TJV:a myös ilman toista komponenttia. Komponenttikombinaatioiden tutkiminen osoitti, että TJV tuottaa herätettä ainoastaan kaksi kertaa kierroksessa, kun painovoima tai vastaava voima kuormittaa roottoria. Tutkitun poikittaissuuntaisen kuorman huomattiin vahvistavan merkittävästi TJV:n herätettä. Kuorman huomattiin kuitenkin myös lisäävän systeemin vaimennusta, ja näin ollen, ei ole aina taattua, että lisätty poikittaissuuntainen kuorma näkyisi TJV:n tuottaman värähtelyn kasvuna. Ei-vakiopoikkileikkauksissa roottoreissa TJV:a aiheuttavien komponenttien vaihekulman kääntämisen huomattiin vähentävän roottorin taivutusjäykkyysvaihtelua.

Julkaisun otsikon käännös	Roottorin asymmetrian ja tuen jäykkyyden vaikutus alikriittiseen värähtelyyn
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Valvoja/neuvonantaja	Kuosmanen, Petri, Vastuuprofessori Viitala, Raine, Ohjaaja
Kustantaja	Aalto University
Painoksen ISBN	978-952-64-0552-0
Sähköinen ISBN	978-952-64-0553-7
Tila	Julkaistu - 2021
OKM-julkaisutyyppi	G5 Artikkeliväitöskirja

Tutkimusalat

alikriittinen värähtely
roottorin asymmetria
säädettävä tuennan jäykkyys
taivutusjäykkyysvaihtelu

Pääsy asiakirjaan

http://urn.fi/URN:ISBN:978-952-64-0553-7

Siteeraa tätä

@phdthesis{cbba036bb52d436fa4be5c5b5218aa55,

title = "Effect of rotor asymmetry and support stiffness on subcritical vibration",

abstract = "The research investigated the effect of support stiffness on dynamic rotor behavior and Bending Stiffness Variation (BSV). Typical rotor tests do not fully prevent the vibration problems caused by BSV and support stiffness in operating conditions. Therefore, vibration problems due to BSV and support stiffness require more profound research and machines peculiar to these particular vibration problems more extensive testing to overcome these problems. In the research, the device for adjustable horizontal stiffness was developed and integrated to a rotor test setup to investigate the effect of support stiffness on rotor behavior. The device could also be used to demonstrate rotor behavior in different operating conditions, and thus to ensure the smooth commissioning of a rotor. The stiffness of the device could continuously be adjusted in the range of 2–18 MN/m, which affected the horizontal natural frequencies of the test rotor over 50%. Additionally, the effect of rotor geometry on the BSV was investigated. Uniform rotor geometry was analytically investigated with the single roundness components, pairs, and the component combination separately. Additionally, the effect of lateral rotor loads on the BSV excitation was investigated experimentally and by simulations, and the excitation generated by BSV of non-uniform rotors were simulated. The developed adjustable stiffness device could widely control its stiffness. The stiffness was observed to affect the natural frequencies of the test rotor differently. The device enabled a new type of rotor testing method in which rotor operability in different operating conditions can be ensured. Additionally, the device can be exploited to optimize rotor dynamic behavior when it is used as a semi-active actuator. The BSV research could separate harmful BSV-producing rotor geometries; the BSV analysis of single roundness components showed that only the second component (ovality) could produce BSV in solid rotors, whereas in tubular rotors, the first component (eccentricity) produced BSV as well. Some component pairs produced BSV also without the second component. The research of the component combinations indicated that BSV produces excitation only twice-per-revolution when gravity or similar load is applied on a rotor. The studied lateral load was observed to magnify BSV excitations significantly. However, the applied lateral load was also observed to increase the damping of the rotor system, and hence, it is not always certain that the magnifying effect of lateral load on bending stiffness variation caused vibration is manifested as increased vibration. In non-uniform rotors, the phase angle of BSV-producing components was observed to decrease overall BSV.",

keywords = "adjustable support stiffness, bending stiffness variation, rotor asymmetry, subcritical vibration, alikriittinen v{\"a}r{\"a}htely, roottorin asymmetria, s{\"a}{\"a}dett{\"a}v{\"a} tuennan j{\"a}ykkyys, taivutusj{\"a}ykkyysvaihtelu, adjustable support stiffness, bending stiffness variation, rotor asymmetry, subcritical vibration",

author = "Risto Viitala",

year = "2021",

language = "English",

isbn = "978-952-64-0552-0",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "143",

address = "Finland",

school = "Aalto University",

}

TY - BOOK

T1 - Effect of rotor asymmetry and support stiffness on subcritical vibration

AU - Viitala, Risto

PY - 2021

Y1 - 2021

N2 - The research investigated the effect of support stiffness on dynamic rotor behavior and Bending Stiffness Variation (BSV). Typical rotor tests do not fully prevent the vibration problems caused by BSV and support stiffness in operating conditions. Therefore, vibration problems due to BSV and support stiffness require more profound research and machines peculiar to these particular vibration problems more extensive testing to overcome these problems. In the research, the device for adjustable horizontal stiffness was developed and integrated to a rotor test setup to investigate the effect of support stiffness on rotor behavior. The device could also be used to demonstrate rotor behavior in different operating conditions, and thus to ensure the smooth commissioning of a rotor. The stiffness of the device could continuously be adjusted in the range of 2–18 MN/m, which affected the horizontal natural frequencies of the test rotor over 50%. Additionally, the effect of rotor geometry on the BSV was investigated. Uniform rotor geometry was analytically investigated with the single roundness components, pairs, and the component combination separately. Additionally, the effect of lateral rotor loads on the BSV excitation was investigated experimentally and by simulations, and the excitation generated by BSV of non-uniform rotors were simulated. The developed adjustable stiffness device could widely control its stiffness. The stiffness was observed to affect the natural frequencies of the test rotor differently. The device enabled a new type of rotor testing method in which rotor operability in different operating conditions can be ensured. Additionally, the device can be exploited to optimize rotor dynamic behavior when it is used as a semi-active actuator. The BSV research could separate harmful BSV-producing rotor geometries; the BSV analysis of single roundness components showed that only the second component (ovality) could produce BSV in solid rotors, whereas in tubular rotors, the first component (eccentricity) produced BSV as well. Some component pairs produced BSV also without the second component. The research of the component combinations indicated that BSV produces excitation only twice-per-revolution when gravity or similar load is applied on a rotor. The studied lateral load was observed to magnify BSV excitations significantly. However, the applied lateral load was also observed to increase the damping of the rotor system, and hence, it is not always certain that the magnifying effect of lateral load on bending stiffness variation caused vibration is manifested as increased vibration. In non-uniform rotors, the phase angle of BSV-producing components was observed to decrease overall BSV.

AB - The research investigated the effect of support stiffness on dynamic rotor behavior and Bending Stiffness Variation (BSV). Typical rotor tests do not fully prevent the vibration problems caused by BSV and support stiffness in operating conditions. Therefore, vibration problems due to BSV and support stiffness require more profound research and machines peculiar to these particular vibration problems more extensive testing to overcome these problems. In the research, the device for adjustable horizontal stiffness was developed and integrated to a rotor test setup to investigate the effect of support stiffness on rotor behavior. The device could also be used to demonstrate rotor behavior in different operating conditions, and thus to ensure the smooth commissioning of a rotor. The stiffness of the device could continuously be adjusted in the range of 2–18 MN/m, which affected the horizontal natural frequencies of the test rotor over 50%. Additionally, the effect of rotor geometry on the BSV was investigated. Uniform rotor geometry was analytically investigated with the single roundness components, pairs, and the component combination separately. Additionally, the effect of lateral rotor loads on the BSV excitation was investigated experimentally and by simulations, and the excitation generated by BSV of non-uniform rotors were simulated. The developed adjustable stiffness device could widely control its stiffness. The stiffness was observed to affect the natural frequencies of the test rotor differently. The device enabled a new type of rotor testing method in which rotor operability in different operating conditions can be ensured. Additionally, the device can be exploited to optimize rotor dynamic behavior when it is used as a semi-active actuator. The BSV research could separate harmful BSV-producing rotor geometries; the BSV analysis of single roundness components showed that only the second component (ovality) could produce BSV in solid rotors, whereas in tubular rotors, the first component (eccentricity) produced BSV as well. Some component pairs produced BSV also without the second component. The research of the component combinations indicated that BSV produces excitation only twice-per-revolution when gravity or similar load is applied on a rotor. The studied lateral load was observed to magnify BSV excitations significantly. However, the applied lateral load was also observed to increase the damping of the rotor system, and hence, it is not always certain that the magnifying effect of lateral load on bending stiffness variation caused vibration is manifested as increased vibration. In non-uniform rotors, the phase angle of BSV-producing components was observed to decrease overall BSV.

KW - adjustable support stiffness

KW - bending stiffness variation

KW - rotor asymmetry

KW - subcritical vibration

KW - alikriittinen värähtely

KW - roottorin asymmetria

KW - säädettävä tuennan jäykkyys

KW - taivutusjäykkyysvaihtelu

KW - adjustable support stiffness

KW - bending stiffness variation

KW - rotor asymmetry

KW - subcritical vibration

M3 - Doctoral Thesis

SN - 978-952-64-0552-0

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

Effect of rotor asymmetry and support stiffness on subcritical vibration

Abstrakti

Tutkimusalat

Pääsy asiakirjaan

Sormenjälki

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