In Squeeze Film Dampers, (SFD), grooves (deep or shallow) are used to feed oil into
the damper and prevent oil starvation within the fluid film lands. In oil seals with film
land of clearance c, short shallow grooves (depth ≤ 15c, length ≤ 30c) are machined to
reduce the cross-coupled stiffness coefficients, and thus improve the seal stability
characteristics. Moreover, test stands for these devices can also incorporate grooves or
recesses as part of oil feeding/ discharge arrangements. A common assumption is that
these grooves do not influence the test system forced response. However, unexpected
large added mass coefficients are reported in these configurations and not adequately
predicted. In the case of grooved oil seals, experimental results also show that
circumferential grooves do aid to reduce cross-coupled force coefficients but to a lesser
extent than predictions otherwise indicate.
A linear fluid inertia model for analysis of multiple-groove SFD or oil seal
configurations is advanced. A perturbation analysis for small motion about a journal
centered and off-centered position yields zeroth and first order flow equations defined at
each individual flow region (land and grooves) of constant clearance ( c ).The analysis
considers both the circumferential and axial dynamic pressure variations across the
groove and land regions. At the groove regions, an effective groove depth ( dη ) and
effective clearance (c d c η η = + ) are defined based on qualitative observations of the
laminar flow pattern through annular cavities. This depth differs from the actual physical
groove depth. The boundary conditions at the inlet and exit plane are a function of the geometric configuration. Integration of the resulting dynamic pressure fields on the
journal surface yields the force coefficients (stiffness, damping, and inertia).
Comparisons between predicted and experimental force coefficients for a grooved
oil seal and a SFD show excellent correlation over a narrow range of effective groove
depths. The results confirm that large added mass coefficients are associated to the
feed/discharge grooves in the scrutinized test configurations. Furthermore, predictions,
benchmarking experimental data, corroborate that short inner land grooves in an oil seal
do not isolate the pressure field of the adjacent film lands, and hence contribute greatly
to the force response of the seal.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-3190 |
| Date | 15 May 2009 |
| Creators | Delgado-Marquez, Adolfo |
| Contributors | San Andres, Luis A. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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