Influence of Groove Size on the Static and Rotordynamic Characteristics of Short, Laminar-Flow Annular Seals

[+] Author and Article Information
Dara W. Childs

The Leland T. Jordan Professor of Mechanical Engineering, Turbomachinery Laboratory, Texas A&M University, College Station, TXdchilds@tamu.edu

Matthew Graviss

SRS Technologies

Luis E. Rodriguez

 Sulzer Hickham, La Porte, TX

J. Tribol 129(2), 398-406 (Jan 05, 2007) (9 pages) doi:10.1115/1.2647471 History: Received May 03, 2006; Revised January 05, 2007

Test results are presented for a smooth seal and three centrally grooved seals that are representative of buffered-flow oil seals in centrifugal compressors. The seals are short (LD0.21), with a diameter of 117mm and a nominal radial clearance of 0.085mm, netting the clearance-to-radius ratio 0.0015. The grooves have groove depth to clearance ratios (DgCr) of 5, 10, and 15. Test conditions include three shaft speeds from 4000rpm to 10,000rpm, three inlet oil pressures from 24bar to 70bar, and seal eccentricity ratios from 0 (centered) to 0.7. Dynamic results include stiffness, damping, and added-mass coefficients; static results include stator position, attitude angles, and seal leakage. Stiffness, damping, and mass coefficients plus leakage are compared for the seal geometries. Results show that all rotordynamic coefficients consistently decrease with increasing seal groove depths, and seal leakage is largely unchanged. Comparisons are also made between experimental results and predictions from a computer program based on a Reynolds + energy equation model. The model includes the assumption that a groove is large enough to create separate lands within the seal, creating a zero or negligible pressure perturbation within the groove. Test results show that even the deepest groove depth tested is not deep enough to satisfy this assumption.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 1

Oil seal assembly (1)

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Figure 2

Grooved seal assemblies [2]

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Figure 3

Rectangular groove geometry

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Figure 4

Eccentricity loci for the grooved seal with Dg∕Cr=10 at 7000rpm

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Figure 5

S−1 versus ε0 for smooth and grooved seals for ω=4000rpm and ΔP=70bars and the four Dg∕Cr ratios

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Figure 6

Measured and predicted leakage for smooth and grooved seals for three supply pressures at 4000rpm

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Figure 7

Measured dynamic coefficients for the grooved seal with Dg∕Cr=5 for ω=10,000rpm, ΔP=70bar, and ε0=0.5

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Figure 8

Kyy versus ε0 for three speeds at ΔP=70bar

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Figure 9

Kxx versus ε0 for three speeds at ΔP=70bar

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Figure 10

Kxy and Kyx versus ε0 for three speeds at ΔP=70bar

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Figure 11

Cyy and Cxx versus ε0 for a running speed of 10,000rpm speeds at ΔP=70bar

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Figure 12

Cyx and Cxy versus ε0 for a rotor speed of 10,000rpm at ΔP=70bars

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Figure 13

Mxx versus ε0 for ΔP=70bars at ω=10,000rpm

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Figure 14

WFR versus ε0 for three ΔPs at ω=10,000rpm

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Figure 15

kyx and Cxx at reduced eccentricity ratios



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