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Research Papers: Gas Turbines: Structures and Dynamics

Investigation of Hydrostatic Fluid Forces in Varying Clearance Turbomachinery Seals

[+] Author and Article Information
S. M. Tibos, C. Georgakis

GE Power,
Newbold Road,
Rugby CV21 2NH, UK

J. A. Teixeira

Centre for Power Engineering,
Cranfield University,
Cranfield MK43 0AL, UK

S. Hogg

Department of Engineering,
Durham University,
Stockton Road,
Durham DH1 3LE, UK

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received December 8, 2016; final manuscript received August 12, 2017; published online November 21, 2017. Assoc. Editor: Alexandrina Untaroiu.

J. Eng. Gas Turbines Power 140(5), 052502 (Nov 21, 2017) (8 pages) Paper No: GTP-16-1576; doi: 10.1115/1.4038136 History: Received December 08, 2016; Revised August 12, 2017

Varying clearance, rotor-following seals are a key technology for meeting the demands of increased machine flexibility for conventional power units. These seals follow the rotor through hydrodynamic or hydrostatic mechanisms. Forward-facing step (FFS) and Rayleigh step designs are known to produce positive fluid stiffness. However, there is very limited modeling or experimental data available on the hydrostatic fluid forces generated from either design. A quasi-one-dimensional (1D) method has been developed to describe both designs and validated using test data. Tests have shown that the FFS and the Rayleigh step design are both capable of producing positive film stiffness and there is little difference in hydrostatic force generation between the two designs. This means any additional hydrodynamic features in the Rayleigh step design should have a limited effect on hydrostatic fluid stiffness. The analytical model is capable of modeling both the inertial fluid forces and the viscous fluid losses, and the predictions are in good agreement with the test data.

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References

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Figures

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Fig. 1

Forward-facing step design

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Fig. 2

Rayleigh step design

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Fig. 3

Algorithm used for solving pressures, Mach number, and mass flow quantities

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Fig. 4

Computational domain showing stations and divisions

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Fig. 5

Setup of 1D tool for the Rayleigh step design

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Fig. 7

Pressure tappings location

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Fig. 8

Blowdown facility schematic

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Fig. 9

Experimental results of dimensionless force against dimensionless clearance for Rayleigh step and FFS designs

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Fig. 10

Experimental results of dimensionless pressure against dimensionless axial position for Rayleigh step and FFS designs at a pressure ratio of 1.4

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Fig. 11

Results comparison of dimensionless pressure against dimensionless axial direction between experiments and analytical models for the FFS design at a pressure ratio of 1.4

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Fig. 12

Results comparison of dimensionless force against dimensionless clearance between experiments and analytical models for the FFS design at a pressure ratio of 1.4

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Fig. 13

Results comparison of dimensionless pressure against dimensionless axial direction between experiments and analytical models for the Rayleigh step design at a pressure ratio of 1.4

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Fig. 14

Results comparison of dimensionless force against dimensionless clearance between experiments and analytical models for the Rayleigh step design at a pressure ratio of 1.4

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Fig. 15

Comparison of dimensionless stiffness against dimensionless clearance for varying land to groove width ratio in the circumferential direction (Rayleigh step design)

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Fig. 16

Comparison of dimensionless stiffness against dimensionless clearance for varying axial position of the step (Rayleigh step design)

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