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research-article

Experimental Force Coefficients for Two Sealed Ends Squeeze Film Dampers (Piston Rings and O-rings): An Assessment of Their Similarities and Differences

[+] Author and Article Information
Luis San Andres

Mechanical Engineering Dept. Texas A&M University College Station, TX 77843, USA
lsanandres@tamu.edu

Bonjin Koo

Mechanical Engineering Dept. Texas A&M University College Station, TX 77843, USA
nightpc@hotmail.com

Sung-Hwa Jeung

Compressor Tech. & Development Ingersoll Rand La Crosse, WI 54601, USA
sean.jeung@gmail.com

1Corresponding author.

ASME doi:10.1115/1.4040902 History: Received July 05, 2018; Revised July 06, 2018

Abstract

Piston rings (PRs) and O-rings (ORs), commonly used as end seals in SFDs for commercial and military gas turbine engines, respectively, amplify viscous damping in a short physical length and while operating with a modicum of lubricant flow. This paper presents experimental force for two identical geometry SFDs with end seals. A computational model reproducing the test conditions delivers force coefficients in agreement with the test data. Archival literature calls for measurement of a single pressure signal to estimate SFD reaction forces. The paper presents force coefficients estimated from (a) measurements of the applied forces and ensuing displacements, and (b) the dynamic pressure recorded at a fixed angular location and "integrated" over the journal surface. Identified damping and inertia coefficients from dynamic pressures show a marked difference from one pressure sensor to another, and vastly disagreeing with test results from the first method or predictions. The rationale for the discrepancy relies on local distortions in the dynamic pressure fields that show zones of oil vapor cavitation at a near zero absolute pressure and/or with air ingestion producing high frequency spikes from bubble collapsing; both phenomena depend on the magnitude of the oil supply pressure. An increase in lubricant supply pressure suppresses both oil vapor cavitation and air ingestion which produces an increase of both damping and inertia force coefficients. Supplying lubricant with a large enough pressure (flow rate) is crucial to avoid the pervasiveness of air ingestion.

Copyright (c) 2018 by ASME
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