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Research Papers: Gas Turbines: Structures and Dynamics

Experimental Results and Computational Fluid Dynamics Simulations of Labyrinth and Pocket Damper Seals for Wet Gas Compression

[+] Author and Article Information
Giuseppe Vannini

GE Oil & Gas,
Via F. Matteucci, 2,
Florence 50127, Italy
e-mail: Giuseppe.Vannini@ge.com

Matteo Bertoneri

GE Oil & Gas,
Via F. Matteucci, 2,
Florence 50127, Italy
e-mail: Matteo.Bertoneri@ge.com

Kenny Krogh Nielsen

Lloyd's Register Consulting,
Strandvejen 104A,
Hellerup DK-2900, Denmark
e-mail: Kenny.Krogh-Nielsen@lr.org

Piero Iudiciani

Lloyd's Register Consulting,
Strandvejen 104A,
Hellerup DK-2900, Denmark
e-mail: Piero.Iudiciani@lr.org

Robert Stronach

Lloyd's Register Consulting,
Strandvejen 104 A,
Hellerup DK-2900, Denmark
e-mail: Robert.Stronach@lr.org

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 14, 2015; final manuscript received August 27, 2015; published online October 27, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 138(5), 052501 (Oct 27, 2015) (13 pages) Paper No: GTP-15-1284; doi: 10.1115/1.4031530 History: Received July 14, 2015; Revised August 27, 2015

The most recent development in centrifugal compressor technology is toward wet gas operating conditions. This means the centrifugal compressor has to manage a liquid phase which is varying between 0% and 3% liquid volume fraction (LVF) according to the most widely agreed definition. The centrifugal compressor operation is challenged by the liquid presence with respect to all the main aspects (e.g., thermodynamics, material selection, thrust load) and especially from a rotordynamic viewpoint. The main test results of a centrifugal compressor tested in a special wet gas loop (Bertoneri et al., 2014, “Development of Test Stand for Measuring Aerodynamic, Erosion, and Rotordynamic Performance of a Centrifugal Compressor Under Wet Gas Conditions,” ASME Paper No. GT2014-25349) show that wet gas compression (without an upstream separation) is a viable technology. In wet gas conditions, the rotordynamic behavior could be impacted by the liquid presence both from a critical speed viewpoint and stability-wise. Moreover, the major rotordynamic results from the previously mentioned test campaign (Vannini et al., 2014, “Centrifugal Compressor Rotordynamics in Wet Gas Conditions,” 43rd Turbomachinery Symposium, Houston) show that both vibrations when crossing the rotor first critical speed and stability (tested through a magnetic exciter) are not critically affected by the liquid phase. Additionally, it was found that the liquid may affect the vibration behavior by partially flooding the internal annular seals and causing a sort of forced excitation phenomenon. In order to better understand the wet gas test outcomes, the authors performed an extensive computational fluid dynamics (CFD) analysis simulating all the different types of balance piston annular seals used (namely, a tooth on stator (TOS) labyrinth seal and a pocket damper seal (PDS)). They were simulated in both steady-state and transient conditions and finally compared in terms of liquid management capability. CFD simulation after a proper tuning (especially in terms of LVF level) showed interesting results which are mostly consistent with the experimental outcome. The results also provide a physical explanation of the behavior of both seals, which was observed during testing.

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References

Figures

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Fig. 1

Test compressor section

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Fig. 2

Test compressor cross-sectional drawing

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Fig. 3

Case 1 waterfall plot with laby seal: 13.5 krpm and 10 bar

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Fig. 4

Case 2 waterfall plot with laby seal: 11.5 krpm and 15 bar

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Fig. 5

Case 3 waterfall plot with laby seal: 11.5 krpm and 10 bar

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Fig. 7

Waterfall plot with laby seal showing dry purging effect in the labyrinth seal

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Fig. 8

Laby and PDS installed on the balance piston

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Fig. 9

Case 1: waterfall plot with PDS: 13.5 krpm and 10 bar

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Fig. 10

Case 2: waterfall plot with PDS: 11.5 krpm and 15 bar

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Fig. 11

Case 3: waterfall plot with PDS 11.5 krpm and 10 bar

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Fig. 12

Slice model for the TOS laby seal

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Fig. 13

45 deg PDS model sectors. The green planar cuts highlight the locations where results are shown in the following figures: Upper: longitudinal cuts, and lower: tangential cuts.

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Fig. 14

Structured mesh for the TOS laby seal

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Fig. 15

Sketch of the forces acting on the liquid in the main flow path

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Fig. 16

Pressure distribution along the laby seal axial length; comparison between experiments and CFD

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Fig. 17

Time-averaged liquid tangential velocity contour plot; seal inlet LVF = 3%

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Fig. 18

Time-averaged liquid axial velocity contour plot; seal inlet LVF = 3%

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Fig. 19

Time-averaged LVF contour plot; seal inlet LVF = 3%

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Fig. 20

Instantaneous LVF contour plot time sequence; seal inlet LVF = 30%

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Fig. 21

Time-averaged LVF contour plot; seal inlet LVF = 30%

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Fig. 22

Time-averaged LVF contour plot and in-plane liquid velocity vector map; seal inlet LVF = 30%

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Fig. 23

Time-averaged liquid tangential momentum contour plot; seal inlet LVF = 30%

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Fig. 24

Time-averaged LVF contour plot; longitudinal cuts; seal inlet LVF = 30%

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Fig. 25

Time-averaged LVF contour plot; tangential cuts; seal inlet LVF = 30%

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Fig. 26

Time-averaged liquid tangential velocity contour plot and in-plane normalized liquid velocity vector map; tangential cuts; seal inlet LVF = 30%

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Fig. 27

Time-averaged liquid tangential momentum; tangential cuts; seal inlet LVF = 30%

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Fig. 28

Emptying mechanism analysis; instantaneous LVF contour plot time sequence; laby case; seal inlet LVF = 3%

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Fig. 29

Emptying mechanism analysis; instantaneous LVF contour plot time sequence; PDS case; longitudinal cuts; seal inlet LVF = 3%

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Fig. 30

Emptying mechanism analysis; global liquid filling parameter α as a function of time; seal inlet LVF = 3%

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