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![Numerical Analysis to Study the Effect of Sag and Non-circular Whirl Orbits on the Damping Performance of a Squeeze Film Damper için kapak resmi Numerical Analysis to Study the Effect of Sag and Non-circular Whirl Orbits on the Damping Performance of a Squeeze Film Damper için kapak resmi](/client/assets/d79c3e4af2b6d196/ctx/images/no_image.png)
Numerical Analysis to Study the Effect of Sag and Non-circular Whirl Orbits on the Damping Performance of a Squeeze Film Damper
Başlık:
Numerical Analysis to Study the Effect of Sag and Non-circular Whirl Orbits on the Damping Performance of a Squeeze Film Damper
Yazar:
Bakhshi, Shashwat, author.
ISBN:
9780438096301
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (84 pages)
Genel Not:
Source: Masters Abstracts International, Volume: 57-06M(E).
Committee members: Urmila Ghia; Jay Kim; Tod Steen.
Özet:
Squeeze Film Dampers, or SFDs, are used in high-speed rotor dynamic systems to reduce rotor vibrations and provide system stability. They are commonly used in aircraft engines to dampen rotor vibrations and provide structural isolation to the rotating shaft system. An SFD consists of a thin pressurized fluid film between two annular cylinders, a stationary housing and a whirling journal within the housing. Sag and non-circular whirl orbits are a real-world phenomenon that occur during an SFD operation. In an ideal scenario, the center of the journal whirls about the center of the housing to produce a uniform squeeze action on the lubricant. However, due to gravity the journal orbit becomes recessed and centers about an arbitrary point between the center of the journal and housing. It is also hard to achieve pure circular whirl orbits in a real-world SFD operation. It is therefore important to understand each of their effects on the damping performance of an SFD. The non-circular whirl orbits are produced using a mathematical equation by adding higher frequency components of the order n = 2 and 3 to the base frequency. Using pure n = 2 and n = 3 harmonics produces non-circular orbits that are symmetric. Pure harmonics are used as a first step in this study to understand the effect of non-circular whirl orbits on the damper performance.
The objective of this thesis is to numerically study the effect of sag and non-circular whirl orbits on the damping performance of an SFD. A transient dynamic mesh approach is used in ANSYS Fluent v15.0, a commercial Computational Fluid Dynamics (CFD) software to simulate the whirling motion of the journal inside an SFD. The numerical methodology is first verified using two theoretical SFD configurations, long and short SFD, for which analytical solutions for pressures and damping forces are derived using Reynolds equation. The derivation of analytical expressions for both configurations limit the effect of fluid inertia. Therefore, numerical pressures and forces are evaluated for a small Re of 0.107. A comparison of the forces for long and short SFD configurations gives an average difference of -0.015% and 1.94%, respectively. The numerical model is subsequently validated against the experimental data for an open-ended, central feed groove SFD available in the literature. Numerical pressures are evaluated at the mid-axial locations of the two SFD lands. The SFD land refers to the area where the squeezing of the lubricant takes place. Upon comparison, the numerical and experimental peak pressures differ by -4.29% and 4.12% in the bottom and top lands, respectively. Following a successful verification and model validation, a numerical analysis is conducted to evaluate the effect of sag and non-circular whirl orbits on the damping performance of an SFD. It is concluded that presence of sag positively impacts the damping performance such that higher average damping forces are observed for sagged whirl orbits compared to non-sagged orbits or whirl orbits about the housing center. However, extent of sag should be moderated during damper design to avoid an over damped damper. This will make the damper system stiff, thus being counter intuitive. A large degree of sag can also lead to an excessive squeeze action on the lubricant. This is can lead to vapor cavitation due to the generation of large amplitudes of negative gage pressure. Lastly, presence sag affects the smooth operation of an SFD because the squeeze action on the lubricant is not uniform. Using pure harmonics to generate non-circular orbits produce a small change in the average damping force when compared to a circular whirl orbit. However, instantaneous damping force changes depending on the instantaneous squeeze action exerted by the journal.
Notlar:
School code: 0045
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(696320.1) | 696320-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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