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Research Papers: Gas Turbines: Structures and Dynamics

An All-Metal Compliant Seal Versus a Labyrinth Seal: A Comparison of Gas Leakage at High Temperatures

[+] Author and Article Information
Luis San Andrés

Mast-Childs Chair Professor
Fellow ASME
Mechanical Engineering Department,
Texas A&M University,
College Station, TX 77843
e-mail: Lsanandres@tamu.edu

Alain Anderson

Halliburton,
Duncan Technology Center,
2600 S. 2nd Street,
Duncan, OK 73536
e-mail: alain.anderson2010@gmail.com

1Work conducted as a graduate student at Texas A&M University, College Station, TX 77843.

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 22, 2014; final manuscript received August 12, 2014; published online November 25, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(5), 052504 (May 01, 2015) (8 pages) Paper No: GTP-14-1428; doi: 10.1115/1.4028665 History: Received July 22, 2014; Revised August 12, 2014; Online November 25, 2014

Parasitic secondary flows (seals' leakage) in centrifugal compressors and gas and steam turbines represent a substantial loss in efficiency and power delivery with an increase in specific fuel consumption. Labyrinth seals (LS) are the most common and inexpensive means of reducing secondary leakage, albeit wearing out with operation and thereby penalizing performance and even affecting rotordynamic stability. The novel hydrostatic advanced low leakage (HALO) seal is an all-metal seal with flexibly supported shoes that enable clearance self-control to effectively reduce leakage, in particular for operation with high pressure ratios and at high surface rotor speeds. This paper presents leakage tests with hot air (max. 300 °C) conducted in a test rig holding a LS and a HALO seal, both of similar diameter, axial length, and clearance. The novel seal leaks much less than the LS as the supply/discharge pressure ratio (Ps/Pa) increases. The leakage reduction is ∼50% for (Ps/Pa) < 2 and continuously dropping to 70% for (Ps/Pa) > 3.0. Thus, the savings in leakage are maximized for operation with a high pressure differential. Leakage measurements with a rotor spinning to a maximum speed of 2700 rpm (surface speed ∼24 m/s) produce a slight decrease in leakage for both seals. Characterization of seal leakage in terms of a flow factor removes the effect of temperature and supply pressure; the LS showing a constant flow factor for (Ps/Pa) > 2. Application of the novel seal technology will aid to increase system efficiency by reducing leakage and will extend maintenance intervals since it eliminates wear of components.

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References

Figures

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Fig. 1

Inner side view of a three teeth LS and schematic view of flow

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Fig. 2

Inner side view of a BS and schematic view of flow

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Fig. 3

Inner side view of a HBS and schematic view of flow

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Fig. 4

Inner side view of a HALO seal and schematic view of flow

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Fig. 5

Cross-sectional views of high temperature seal test rig. Top: side whole rig, bottom: isometric view with flow path shown.

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Fig. 6

Cross section view of tapered roller bearing supporting the rotor

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Fig. 7

Steel LS: dimensions (mm (in)) and cross section view of teeth

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Fig. 8

All-metal (HALO) seal with insets showing its axial profile and flow path

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Fig. 13

HALO seal and LS: mass flow rate (m˙) versus pressure ratio, pr = Ps/Pa. Air at inlet temperature = 30 °C, 100 °C, 200 °C, and 300 °C. No disk rotation.

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Fig. 12

HALO seal: flow factor (Ф) versus pressure ratio, pr = Ps/Pa. Tests at (a) 100 °C and (b) 200 °C for various rotor speeds.

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Fig. 11

LS: flow factor (Ф) versus pressure ratio, pr = Ps/Pa. Tests at (a) 100 °C and (b) 300 °C for various rotor speeds.

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Fig. 10

HALO seal: mass flow rate (m˙) versus pressure ratio, pr = Ps/Pa. Tests at (a) 100 °C and (b) 200 °C for three rotor speeds. Discharge at ambient pressure (Pa).

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Fig. 9

LS: mass flow rate (m˙) versus pressure ratio, pr = Ps/Pa. Tests at (a) 100 °C and (b) 300 °C for three rotor speeds. Discharge at ambient pressure (Pa).

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Fig. 14

HALO seal and LS: flow factor (Ф) versus pressure ratio, pr = Ps/Pa. Air at inlet temperature = 30 °C, 100 °C, 200 °C, and 300 °C. No disk rotation.

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