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Research Papers: Gas Turbines: Structures and Dynamics

Leakage and Rotordynamic Force Coefficients of A Three-Wave (Air in Oil) Wet Annular Seal: Measurements and Predictions

[+] Author and Article Information
Xueliang Lu

Mechanical Engineering Department,
Texas A&M University,
College Station, TX 77843
e-mail: luliang413@gmail.com

Luis San Andrés

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

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 30, 2018; final manuscript received August 1, 2018; published online October 4, 2018. Editor: Jerzy T. Sawicki.

J. Eng. Gas Turbines Power 141(3), 032503 (Oct 04, 2018) (11 pages) Paper No: GTP-18-1530; doi: 10.1115/1.4041270 History: Received July 30, 2018; Revised August 01, 2018

In subsea environments, multiphase pumps and compressors add pressure to the process fluid, thus enabling long distance tie back systems that eliminate topside oil and gas separation stations. One challenge to construct a reliable multiphase pump or a reliable wet gas compressor is that the first must handle, without process upset, a mixture whose gas volume fraction (GVF) changes suddenly; while the other must remain stable while working with a liquid volume fraction (LVF) changing over long periods of time. The mixture GVF/LVF affects the static and dynamic forced performance of secondary flow components, namely seals, and which could lead to an increase in both rotor lateral or axial vibrations, thus compromising system reliability and availability. The current research is a planned endeavor toward developing seal configurations amenable to maintain rotor dynamic characteristics during changes in the contents of flow components. This paper extends prior work with uniform clearance annular seals and presents the static and dynamic forced performance of a three-wave surface annular seal designed to deliver a significant centering stiffness. The test element has length L = 43.4 mm, diameter D = 127 mm, and mean radial clearance cm=0.191 mm. At a shaft speed of 3.5 krpm (23 m/s surface speed), an air in ISO VG 10 oil mixture with an inlet GVF, 0 to 0.9, feeds the seal at 2.5 bara pressure and 37 °C temperature. The mixture mass flow rate decreases continuously with an increase in inlet GVF; shaft speed has little effect on it. Dynamic load tests serve to identify the seal dynamic force coefficients. The liquid seal (GVF = 0) shows frequency independent force coefficients. However, operation with a mixture produces stiffnesses that vary greatly with excitation frequency, in particular the direct one that hardens. The direct damping coefficients are not functions of frequency albeit dropping rapidly in magnitude as the GVF increases. The work also compares the performance of the wavy seal against those of two other seals: one with clearance equal to the mean clearance of the wavy seal, and the other with a large clearance emulating a fully worn wavy seal. The small clearance seal leaks 20% less than the wavy seal, whereas the leakage of the worn seal is twofold that of the wavy seal. For the three seals, the leakage normalized with respect to a pure liquid condition collapses into a single curve. The wavy seal produces the greatest direct stiffness and damping coefficients, whereas the worn seal produces the smallest force coefficients. Derived from a homogeneous mixture bulk flow model, predicted force coefficients for the three-wave seal match well with the test data for operation with a pure oil and an inlet GVF 0.2. For operation with GVF > 0.2, the discrepancy between the prediction and experimental data grows rapidly. The extensive test campaign reveals a wavy-surface seal offers a centering stiffness ability, a much desired feature in vertical submersible pumps that suffer from persistent static and dynamic stability issues.

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References

Gong, H. , Falcone, G. , Teodoriu, C. , and Morrison, G. L. , 2012, “ Comparison of Multiphase Pumping Technologies for Subsea and Downhole Applications,” Oil Gas Facilities, 1(1), pp. 36–46. [CrossRef]
Bertoneri, M. , Wilcox, M. , Toni, L. , and Beck, G. , 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.
Vannini, G. , Bertoneri, M. , Del Vescovo, G. , and Wilcox, M. , 2014, “ Centrifugal Compressor Rotordynamics in Wet Gas Conditions,” 43rd Turbomachinery and 30th Pump Users Symposium, Houston, TX, Sept. 23–25. http://oaktrust.library.tamu.edu/bitstream/handle/1969.1/162697/TurboLecture11.pdf?sequence=1&isAllowed=y
Iwatsubo, T. , and Nishino, T. , 1993, “ An Experimental Study on the Static and Dynamic Characteristics of Pump Annular Seals,” Seventh Workshop on Rotordynamic Instability Problems in High Performance Turbomachinery, College Station, TX, May 10–12, pp. 30–45.
Brenne, L. , Bjorge, T. , and Gilarranz, J. , 2005, “ Performance Evaluation of a Centrifugal Compressor Operating Under Wet Gas Conditions,” 34th Turbomachinery Symposium, Houston, TX, Sept. 12–15, pp. 111–120.
Vannini, G. , Bertoneri, M. , Nielsen, K. K. , Ludiciani, P. , and Stronach, R. , 2016, “ Experimental Results and Computational Fluid Dynamics Simulations of Labyrinth and Pocket Damper Seals for Wet Gas Compression,” ASME J. Eng. Gas Turbines Power, 138(5), p. 052501. [CrossRef]
Ransom, D. , Podesta, L. , Camatti, M. , Wilcox, M. , Bertoneri, M. , and Bigi, M. , 2011, “ Mechanical Performance of a Two Stage Centrifugal Compressor Under Wet Gas Conditions,” 40th Turbomachinery Symposium, Houston, TX, Sept. 12–15.
San Andrés, L. , 2012, “ Rotordynamic Force Coefficients of Bubbly Mixture Annular Pressure Seals,” ASME J. Eng. Gas Turbines Power, 134(2), p. 022503. [CrossRef]
Arghir, M. , Zerarka, E. , and Pieanu, G. , 2011, “ Rotordynamic Analysis of Textured Annular Seals With Multiphase (Bubbly) Flow,” INCAS Bull., 3(3), pp. 3–13. [CrossRef]
San Andrés, L. , Lu, X. , and Liu, Q. , 2016, “ Measurements of Flow Rate and Force Coefficients in a Short-Length Annular Seal Supplied With a Liquid/Gas Mixture (Stationary Journal),” Tribol. Trans, 59(4), pp. 758–767. [CrossRef]
San Andrés, L. , and Lu, X. , 2018, “ Leakage, Drag Power and Rotordynamic Force Coefficients of an Air in Oil (Wet) Annular Seal,” ASME J. Eng. Gas Turbines Power, 140(1), p. 012505. [CrossRef]
Voigt, A. J. , Mandrum-Polsen, C. , Nielsen, K. K. , and Santos, I. F. , 2017, “ Design and Calibration of a Full Scale Active Magnetic Bearing Based Test Facility for Investigating Rotordynamic Properties of Turbomachinery Seals in Multiphase Flow,” ASME J. Eng. Gas Turbinnes Power, 139(5), p. 052505. [CrossRef]
Zhang, M. , Mclean , J. E., Jr. , and Childs, D. , 2017, “ Experimental Study of the Static and Dynamic Characteristics of a Long Smooth Seal With Two-Phase, Mainly-Air Mixtrues,” ASME J. Eng. Gas Turbines Power, 139(12), p. 122504. [CrossRef]
Leader, M. E. , Conner, K. J. , and Lucas, J. D. , 2010, “ Evaluating and Correcting Subsynchronous Vibration in Vertical Pumps,” 26th International Pump Users Symposium, Texas A&M University, Houston, TX, pp. 15–18.
Dimofte, F. , 1994, “ Wave Journal Bearing With Compressible Lubricant—Part I: The Wave Bearing Concept and a Comparison to the Plain Circular Bearing,” Tribol. Trans, 38(1), pp. 153–160. [CrossRef]
Ene, N. M. , Dimofte, F. , and Keith , T. G., Jr. , 2008, “ A Stability Analysis for a Hydrodynamic Three-Wave Journal Bearing,” Trib. Int., 41(5), pp. 434–442. [CrossRef]
Childs, D. W. , Norrbin, C. S. , and Philips, S. , 2014, “ A Lateral Rotordynamics Primer on Electric Submersible Pumps (ESPs) for Deep Subsea Applications,” 43rd Turbomachinery & 30th Pump Symposia, Houston, TX, Sept. 23–25. https://pdfs.semanticscholar.org/1a84/018a79cf26f9743f7165e8ae59cafa045feb.pdf
San Andrés, L. , Lu, X. , and Zhu, J. , 2018, “ On the Leakage and Rotordynamic Force Coefficients of Pump Annular Seals Operating With Air/Oil Mixtures: Measurements and Predictions,” Second ASIA Turbomachinery & Pump Symposium, Singapore, Mar. 22–25.
San Andrés, L. , 2010, “ Experimental Identification of Bearing Force Coefficients,” Modern Lubrication Theory, Texas A&M University Digital Libraries, College Station, TX.
San Andrés, L. , Diaz, S. E. , and Rodriguez, L. E. , 2001, “ Sine Sweep Load vs. Impact Excitations and Their Influence on the Damping Coefficients of a Bubbly Oil Squeeze Film Damper,” Tribol. Trans, 44(4), pp. 692–698. [CrossRef]

Figures

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Fig. 1

Geometry of a three-wave annular seal. L = 43.4 mm, D = 127 mm, cmax = 0.274 mm, cmin = 0.108 mm, cm = 0.191 mm, ew = 0.083 mm, nw = 3.

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Fig. 2

Design and measured clearance profile of three-wave seal. L = 43.4 mm, D = 127 mm, cmax = 0.274 mm, cmin = 0.108 mm, cm = 0.191 mm, ew = 0.083 mm, nw = 3. Line: design clearance, symbol: measured clearance.

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Fig. 3

Isometric view of test rig with shakers attached [18]

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Fig. 4

(a) Cut view of test seal assembly with lubricant flow path, (b) section A-A with seal installed in housing (L = 43.4 mm, D = 127 mm, cm = 0.191 mm) [18]

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Fig. 5

(a) Three-wave annular seal and uniform clearance annular seal: normalized leakage (m¯˙m) versus mixture inlet GVF [18]. (b) Zoomed inset showing m¯˙m for 0.8 ≤ GVF ≤ 1. Supply pressure (Ps) 2 bara, discharge pressure (Pa) = 1 bara. Shaft speed N = 0 to 4 krpm (ΩR = 26.6 m/s).

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Fig. 6

Three-wave seal: direct dynamic stiffness (HXX⫫) and HYY⫫) versus frequency (ω). Inlet GVF = 0 to 0.9. Shaft speed =3.5 krpm (ΩR = 23.3 m/s). Supply pressure (Ps) = 2.5 bara, discharge pressure (Pa) = 1 bara.

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Fig. 7

Three-wave seal: direct dynamic stiffness (HXX⫫ and HYY⫫) versus inlet GVF, and operation at a low whirl frequency ω = 20 Hz (ω/Ω ∼0.34). Shaft speed = 3.5 krpm (ΩR = 23.3 m/s). Supply pressure (Ps) = 2.5 bara, discharge pressure (Pa) =1 bara.

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Fig. 8

Three-wave seal: cross coupled dynamic stiffness (HXY⫫ and −HYX⫫) versus frequency (ω). Inlet GVF = 0–0.9. Shaft speed = 3.5 krpm (ΩR = 23.3 m/s). Supply pressure (Ps) = 2.5 bara, discharge pressure (Pa) = 1 bara.

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Fig. 9

Three-wave seal: direct damping coefficient (C = H⊥/ω) versus frequency (ω). Inlet GVF = 0–0.9. Shaft speed = 3.5 krpm (ΩR = 23.3 m/s). Supply pressure (Ps) = 2.5 bara, discharge pressure (Pa) = 1 bara.

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Fig. 10

Three-wave seal: effective damping coefficients CeffXX = (CXX − KXY/ω), CeffYY = (CXX + KXY/ω) versus frequency (ω). Inlet GVF = 0–0.9. Shaft speed = 3.5 krpm (ΩR = 23.3 m/s). Supply pressure (Ps) = 2.5 bara, discharge pressure (Pa) =1 bara.

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Fig. 11

Three-wave seal and two uniform clearance seals: direct dynamic stiffnesses versus frequency (ω). Inlet GVF = 0, 0.4, 0.8. Shaft speed = 3.5 krpm (ΩR = 23.3 m/s). Supply pressure (Ps) = 2.5 bara, exit pressure (Pa) = 1 bara.

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Fig. 12

Three-wave seal and two uniform clearance seals: cross-coupled dynamic stiffnesses versus frequency (ω). Inlet GVF = 0, 0.4, 0.8. Shaft speed = 3.5 krpm (ΩR = 23.3 m/s). Supply pressure (Ps) = 2.5 bara, exit pressure (Pa) = 1 bara.

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Fig. 13

Three-wave seal and two uniform clearance seals: direct damping coefficient versus frequency (ω). Inlet GVF = 0, 0.4, 0.8. Shaft speed = 3.5 krpm (ΩR = 23.3 m/s). Supply pressure (Ps) = 2.5 bara, exit pressure (Pa) = 1 bara.

Grahic Jump Location
Fig. 14

Three-wave seal and two uniform clearance seals: effective damping versus frequency (ω). Inlet GVF = 0, 0.4, 0.8. Shaft speed = 3.5 krpm (ΩR = 23.3 m/s). Supply pressure (Ps) = 2.5 bara, exit pressure (Pa) = 1 bara.

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