NDLI: Damping and Inertia Coefficients for Two End Sealed Squeeze Film Dampers With a Central Groove: Measurements and Predictions

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Andrés, Luis San Seshagiri, Sanjeev
Copyright Year	2013
Abstract	Aircraft engine rotors, invariably supported on rolling element bearings with little damping, are particularly sensitive to rotor imbalance and sudden maneuver loads. Most engines incorporate Squeeze Film Dampers (SFDs) as means to dissipate mechanical energy from rotor motions and to ensure system stability. The paper quantifies experimentally the dynamic forced performance of two end sealed SFDs with dimensions and operating envelope akin to those in actual jet engine applications. The current experimental results complement and extend prior research conducted with open ends SFDs [21]. In the tests, two journals make for two SFD configurations, both with diameter D = 127 mm and nominal radial film clearance c = 0.127 mm. One short length damper has film lands with extent L = 12.7 mm, while the other has 25.4 mm (= 2L) land lengths. A central groove with length LG = L and depth at ¾ L separates the film lands. A light viscosity lubricant is supplied into the central groove via 3 orifices, 120° apart, and then flows through the film lands whose ends are sealed with tight piston rings. The oil pushes through the piston rings to discharge at ambient pressure. In the tests, a static load device pulls the damper structure to increasing eccentricities (max. 0.38c) and external shakers exert single-frequency loads, 50 Hz–250 Hz, inducing circular orbits with amplitudes equaling ∼5% of the film clearance. The lubricant feed and groove pressures and flow rates through the top and bottom film lands are recorded to determine the flow resistances through the film lands and the end seals. Measured dynamic pressures in the central groove are as large as those in the film lands thus demonstrating a strong flow interaction, further intensified by the piston ring end seals which are effective in preventing side leakage. Dynamic pressures and reaction loads are substantially higher than those recorded with the open ends dampers. Comparisons to test results for two identical damper configurations but open ended [21] demonstrate at least a thrice increase in direct damping coefficients and no less than a twice increment in added mass coefficients. Predictions from a physics based model that includes the central groove, the lubricant feed holes and the end seals’ flow conductances are in agreement with the test results for the short length damper. For the long damper, the predicted damping coefficients are in good agreement with the measurements while the added masses are under predicted by ∼25%.
Sponsorship	International Gas Turbine Institute
File Format	PDF
ISBN	9780791855270
DOI	10.1115/GT2013-94273
Volume Number	Volume 7B: Structures and Dynamics
Conference Proceedings	ASME Turbo Expo 2013: Turbine Technical Conference and Exposition
Language	English
Publisher Date	2013-06-03
Publisher Place	San Antonio, Texas, USA
Access Restriction	Subscribed
Subject Keyword	Damping Leakage Viscosity Inertia (mechanics) Stability Dampers Lubricants Rotors Clearances (engineering) Dimensions Aircraft engines Flow (dynamics) Pressure Stress Engines Jet engines Physics Piston rings Orifices Rolling bearings
Content Type	Text
Resource Type	Article

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