0
Research Papers: Gas Turbines: Structures and Dynamics

Rotordynamic Computational and Experimental Characterization of a Convergent Honeycomb Seal Tested With Negative Preswirl, High Pressure With Static Eccentricity and Angular Misalignment

[+] Author and Article Information
Giuseppe Vannini

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

Carlo Mazzali

STATOIL,
Martin Linges Vei 33,
Fornebu 1364, Norway
e-mail: cmaz@statoil.com

Harald Underbakke

STATOIL,
Forusbeen 50,
Stavanger 4035, Norway
e-mail: hun@statoil.com

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received June 20, 2016; final manuscript received August 31, 2016; published online December 1, 2016. Editor: David Wisler.

J. Eng. Gas Turbines Power 139(5), 052502 (Dec 01, 2016) (10 pages) Paper No: GTP-16-1248; doi: 10.1115/1.4034965 History: Received June 20, 2016; Revised August 31, 2016

Hole-pattern or honeycomb seals have been commonly used for many years in the Oil & Gas industry as damper seals for turbomachinery. The main motivation has been to introduce additional damping to improve the shaft rotordynamic stability operating under high-pressure conditions. Experience has shown that the dynamic and even static characteristics of those seals are very sensitive to the operating clearance profile as well as the installation tolerances. Rotordynamic stability is related not only to the seal effective damping but to the effective stiffness as well. In fact, for this kind of seal, the effective stiffness can be high enough to alter the rotor system's natural frequency. The seal stiffness is strictly related to the tapering contour: if the clearance profile changes from divergent to convergent, the effective stiffness may change from a strong negative to a strong positive magnitude, thus avoiding the rotor natural frequency drop as it is detrimental for the stability. Unfortunately, the effective damping is reduced at the same time but this effect can be mitigated using proper devices to keep the preswirl low or even negative (e.g., swirl brakes and shunt holes). This paper presents the results from an extended test campaign performed in a high-speed rotor test rig equipped with active magnetic bearings (AMBs) working under high pressure (14 krpm, 200 bar gas inlet pressure), with the aim to validate the rotordynamic characteristics of a negative preswirl, convergent honeycomb seal and demonstrate its ability to effectively act as a gas bearing as well as a seal. The test plan included variations of inlet pressure, differential pressure (given the same inlet pressure), as well as rotational speed in order to fully validate the seal behavior. This kind of test was performed in a “dynamic mode” that is to say exciting the spinning test rotor through a pair of AMBs along linear orbits. Additionally, the impact of the seal to rotor static eccentricity and the seal to rotor angular misalignment were both experimentally investigated and compared to relevant computational fluid dynamics (CFD) simulations. This kind of test was performed in a “static mode,” that is to say imposing through the AMBs the required eccentricity/angular misalignment and then measuring the forces needed to keep the rotor in the original position. Dynamic mode test was also performed in order to check the impact of the seal static eccentricity on its dynamic behavior. Finally, the test results were compared with predictions from a state of the art bulk-flow code in order to check the predictability level for future design applications.

Copyright © 2017 by ASME
Your Session has timed out. Please sign back in to continue.

References

Childs, D. , 1978, “ The Space Shuttle Main Engine High Pressure Fuel Turbopump Rotordynamic Instability Problem,” ASME J. Eng. Gas Turbines Power, 100(1), pp. 48–57. [CrossRef]
Childs, D. , Nelson, C. , Nicks, C. , Scharrer, J. , Elrod, D. , and Hale, K. , 1986, “ Theory Versus Experiment for the Rotordynamic Coefficients of Annular Gas Seals: Part 1—Test Facility and Apparatus,” ASME J. Tribol., 108(3), pp. 426–432. [CrossRef]
Childs, D. , and Scharrer, J. , 1986, “ An Iwatsubo Based Solution for Labyrinth Seal—Comparison to Experimental Results,” ASME J. Eng. Gas Turbines Power, 108(2), pp. 325–331. [CrossRef]
Ha, T.-W. , and Childs, D. , 1992, “ Friction Factor Data for Flat Plate Tests of Smooth and Honeycomb Surfaces,” ASME J. Tribol., 114(4), pp. 722–730. [CrossRef]
Kleynhans, G. , and Childs, D. , 1997, “ The Acoustic Influence of Cell Depth on the Rotordynamic Characteristics of Smooth Rotor/Honeycomb Stator Annular Gas Seals,” ASME J. Eng. Gas Turbines Power, 119(4), pp. 949–957. [CrossRef]
Dawson, M. , Childs, D. , Holt, C. , and Phillips, S. , 2002, “ Theory Versus Experiment for the Dynamic Impedances of Annular Gas Seals: Part I—Test Facility and Apparatus,” ASME J. Eng. Gas Turbines Power, 124(4), pp. 958–963. [CrossRef]
Weatherwax, M. , and Childs, D. , 2003, “ The Influence of Eccentricity on the Leakage and Rotordynamic Coefficients of a High Pressure, Honeycomb, Annular Gas Seal. Measurements Versus Predictions,” ASME J. Tribol., 125(2), pp. 422–429. [CrossRef]
Sprowl, B. , and Childs, D. , 2007, “ A Study of the Effects of Inlet Preswirl on the Dynamic Coefficients of a Straight Bore Honeycomb Gas Damper Seal,” ASME J. Eng. Gas Turbines Power, 129(1), pp. 220–229. [CrossRef]
Brown, P. , and Childs, D. , 2012, “ Measurement Versus Predictions of Rotordynamic Coefficients of a Hole-Pattern Gas Seal With Negative Preswirl,” ASME J. Eng. Gas Turbines Power, 134(12), p. 122503. [CrossRef]
Childs, D. , Arthur, S. , and Mehta, N. , 2013, “ The Impact of Hole Depth on the Rotordynamic and Leakage Characteristics of Hole Pattern Stator Gas Annular Seals,” ASME J. Eng. Gas Turbines Power, 136(4), p. 042501. [CrossRef]
Childs, D. W. , Shin, Y. S. , and Seifert, B. , 2006, “ A Design to Improve the Effective Damping Characteristics of Hole-Pattern-Stator Annular Gas Seals,” ASME Paper No. GT2006-90778.
Childs, D. W. , Shin, Y. S. , and Wade, J. , 2006, “ A Design to Increase the Static Stiffness of Hole Pattern Stator Gas Seals,” ASME Paper No. GT2006-90778.
Camatti, M. , Vannini, G. , Fulton, J. W. , and Hopenwasser, F. , 2003, “ Instability of a High Pressure Compressor Equipped With Honeycomb Seals,” Proceedings of the 32nd Turbomachinery Symposium, Houston, TX, Sept. 8–11, pp. 39–48.
Moore, J. J. , Camatti, M. , Smalley, A. J. , Vannini, G. , and Vermin, L. L. , 2006, “ Investigation of a Rotordynamic Instability in a High Pressure Centrifugal Compressor Due to Damper Seal Clearance Divergence,” Seventh IFToMM-Conference on Rotor Dynamics, Vienna (IFToMM), Austria, Sept. 25–28, Paper No. 130.00.
Kocur, J. , and Hayles, G. , 2004, “ Low Frequency Instability in a Process Compressor,” 33rd Turbomachinery Symposium, Houston, TX, Sept 21–23, pp. 25–32.
Lindsey, T. , and Childs, D. , 1995, “ The Effects of Converging and Diverging Axial Taper on the Rotordynamic Coefficients of Liquid Annular Pressure Seals: Theory Versus Experiment,” ASME J. Vib. Acoust., 122(2), pp. 126–131. [CrossRef]
Childs, D. , and Dressman, J. B. , 1985, “ Convergent-Tapered Annular Seals: Analysis and Testing for Rotordynamic Coefficients,” ASME J. Tribol., 107(3), pp. 307–316. [CrossRef]
Stangeland, M. , 1994, “ Axially Fed Hydrostatic Bearing/Seal,” U.S. Patent No. 5,310,265.
Underbakke, H. , 2008, “ Bearing System for Rotor in Rotating Machines,” U.S. Patent No. 8,882,446.
Smalley, A. , Camatti, M. , Childs, D. , Hollingsworth, J. , Vannini, G. , and Carter, J. , 2006, “ Dynamic Characteristics of the Diverging Taper Honeycomb-Stator Seal,” ASME J. Turbomach., 128(4), pp. 717–724. [CrossRef]
Nielsen, K. K. , Jønck, K. , and Underbakke, H. , 2012, “ Hole-Pattern and Honeycomb Seal Rotordynamic Forces: Validation of CFD-Based Prediction Techniques,” ASME Paper No. GT2012-69878.
Childs, D. , and Wade, J. , 2004, “ Rotordynamic-Coefficient and Leakage Characteristics for Hole-Pattern Stator Annular Gas Seals—Measurements Versus Predictions,” ASME J. Tribol., 126(2), pp. 326–333. [CrossRef]
Yu, Z. , and Childs, D. , 1998, “ A Comparison of Experimental Rotordynamic Coefficients and Leakage Characteristics between Hole-Pattern Gas damper Seals and a Honeycomb Seal,” ASME J. Eng. Gas Turbines Power, 120(4), pp. 778–783. [CrossRef]
Childs, D. , and Arthur, S. P. , 2013, “ Static Destabilizing Behavior for Gas Annular Seals at High Eccentricity Ratios,” ASME Paper No. GT2013-94201.
Arghir, M. , and Mariot, A. , 2014, “ About the Negative Direct Static Stiffness of Highly Eccentric Straight Annular Seals,” ASME Paper No. GT2014-27070.
Vannini, G. , Cioncolini, S. , Calicchio, V. , and Tedone, F. , 2011, “ Development of an Ultra-High Pressure Rotordynamic Test Rig for Centrifugal Compressors Internal Seals Characterization,” 40th Turbomachinery Symposium, Houston, TX, Sept. 12–15, pp. 46–59.
Vannini, G. , Cioncolini, S. , Del Vescovo, G. , and Rovini, M. , 2014, “ Labyrinth Seal and Pocket Damper Seal High Pressure Rotordynamic Test Data,” ASME J. Eng. Gas Turbines Power, 136(2), p. 022501. [CrossRef]

Figures

Grahic Jump Location
Fig. 1

Constant clearance seal profile with eccentric rotor

Grahic Jump Location
Fig. 2

Convergent clearance seal profile with eccentric rotor

Grahic Jump Location
Fig. 3

Schematic of convergent seal in tilted configuration

Grahic Jump Location
Fig. 4

Seal pressure field—50% eccentricity

Grahic Jump Location
Fig. 5

Seal pressure drop versus seal length

Grahic Jump Location
Fig. 6

Effective stiffness for different seal preswirls

Grahic Jump Location
Fig. 7

Effective damping for different seal preswirls

Grahic Jump Location
Fig. 8

Effective stiffness versus shaft tilt

Grahic Jump Location
Fig. 9

Effective damping versus shaft tilt

Grahic Jump Location
Fig. 10

Preswirl and pressure trends during a typical experiment

Grahic Jump Location
Fig. 11

Instrumented honeycomb seal

Grahic Jump Location
Fig. 12

Seal inlet–outlet clearance measurements

Grahic Jump Location
Fig. 13

Experimental centered versus eccentric dynamic coefficients

Grahic Jump Location
Fig. 14

Effective stiffness: test versus predictions

Grahic Jump Location
Fig. 15

Effective damping: test versus predictions

Grahic Jump Location
Fig. 16

Conceptual scheme of static mode test

Grahic Jump Location
Fig. 17

Experimental seal reaction forces due to eccentricity and tilt

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In