Squeeze Film Damper Bearing With Double-Ended Beam Springs: Part II — Experimental Validation

Squeeze film damper (SFD) bearings are widely used in industry to enhance rotor dynamic stability when operating at super-critical speeds. This study examines an SFD bearing design with load cell type centering springs placed external to the squeeze film and in parallel with O-ring seals. The SFD bearing design minimizes the use of O-rings as a support and centering device relying primarily on compact external springs for support that can be independently adjusted to ensure centered operation of the SFD journal. A hydrodynamic tilting pad journal bearing (TPJB) is a part of the design and placed in series with the SFD.

The objective of the SFD is to achieve rotor dynamic stability for rotors that would otherwise not be stable.  Critical performance parameters include overall SFD stiffness and damping for control of the unbalance response and rotor dynamic stability.  The critical design parameters, which influence the performance of the SFD include geometric envelope, length, diameter, clearance, oil feed, and spring design.  Spring design and analysis is a specific focus and includes evaluation of centering capability, spring rate and spring life [1].

A pair of 3.5 inch SFD bearings and a test rotor were designed, manufactured and tested.  The spring design stiffness was validated through a static spring compression test.  Spring life was assessed through a high cycle fatigue test. And centering of the SFD bearing assembly was confirmed through a centering bench test.

Unbalance response correlation and logarithmic decrement (logdec) measurement using the operational modal analysis (OMA) method were employed for the rotor-dynamic tests. A good agreement was seen between analysis and experimental measurement. Full film and pi-film damping models were considered.  It was found that the full film (uncavitated) damping model [2] provided the best match to the measured unbalance response and measured logarithmic decrement.

[1] Squeeze Film Damper Bearing with Load Cell Type Centering Springs: Part 1–Design and Analysis