Research Papers: Gas Turbines: Structures and Dynamics

Development of Scallop Cut Type Damper Seal for Centrifugal Compressors

[+] Author and Article Information
Naohiko Takahashi

Turbomachinery R&D Center,
Infrastructure Systems Company,
Hitachi, Ltd.,
603 Kandatsu-machi,
Tsuchiura-shi, Ibaraki-ken 300-0013, Japan
e-mail: naohiko.takahashi.qb@hitachi-pt.com

Haruo Miura

Compressor Division,
Infrastructure Systems Company,
Hitachi, Ltd.,
603 Kandatsu-machi,
Tsuchiura-shi, Ibaraki-ken 300-0013, Japan
e-mail: haruo.miura.wm@hitachi-pt.com

Mitsuhiro Narita

Compressor Division,
Infrastructure Systems Company,
Hitachi, Ltd.,
603 Kandatsu-machi,
Tsuchiura-shi, Ibaraki-ken 300-0013, Japan
e-mail: mitsuhiro.narita.nq@hitachi-pt.com

Noriyo Nishijima

Planning Office,
Hitachi Research Laboratory,
Hitachi, Ltd.,
1-1, Omika-cho 7 chome,
Hitachi-shi, Ibaraki-ken 319-1292, Japan
e-mail: noriyo.nishijima.sj@hitachi.com

Yohei Magara

Reliability Science Research Department,
Hitachi Research Laboratory,
Hitachi, Ltd.,
832-2 Horiguchi,
Hitachinaka-shi, Ibaraki-ken 312-0034, Japan
e-mail: yohei.magara.bc@hitachi.com

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 18, 2014; final manuscript received August 1, 2014; published online October 7, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(3), 032509 (Oct 07, 2014) (9 pages) Paper No: GTP-14-1406; doi: 10.1115/1.4028448 History: Received July 18, 2014; Revised August 01, 2014

This paper deals with a new type of damper seal developed for a high-pressure centrifugal compressor. Honeycomb seals and hole pattern seals are popularly used as damper seals and provide superior rotordynamic damping characteristics. Honeycomb seals are expensive because the manufacturing process is complex. Hole pattern seals are easier to manufacture, but they are still expensive. Use of a scallop pattern is one way to reduce manufacturing cost and time. A new seal that has a scallop pattern and small teeth on the stator surface is proposed. This pattern is cut on the stator surface using a disk type tool. To estimate the rotordynamic coefficients of this new seal, a bulk flow model code that is based on a two-control-volume model developed by Matsuda for labyrinth seals was newly developed. This model uses the Hirs model for the viscous shear stresses. The friction factor coefficients for the rotor surface, the stator surface, and the surface between the two-control-volumes were determined by computational fluid dynamics (CFD) steady analysis. The rotordynamic coefficients can also be obtained by using CFD perturbation analysis. The high accuracy of the bulk flow model was demonstrated by comparing its results with CFD perturbation analysis results. In the perturbation analysis, the whirling motion was treated as a steady-state problem by using a rotating frame of reference. For the damper seal, the rotor surface and its neighboring region were treated with a rotating frame of reference and the neighboring region of the stator was treated with a stationary frame of reference. The damping property of the new seal was evaluated by conducting rotor stability tests using a high-pressure compressor with an electromagnetic exciter. The new seal equipped with swirl brakes was used for the balance piston of the compressor. Stability was evaluated by exciting the rotor during operation and identifying the eigenvalues of the rotor. The experimental results showed that the new seal increases damping. Comparison of the damping effect with calculations based on the bulk flow analysis showed good agreement.

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Fig. 2

Axial flow in the seal

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Fig. 1

New damper seal with scalloped grooves

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Fig. 3

Bulk flow model with two-control-volumes

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Fig. 5

Cavity space to be modeled by control volume 2

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Fig. 4

Rotor whirling motion and aerodynamic load

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Fig. 13

Comparison of seal rotordynamic calculation results

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Fig. 7

Circumferential flow rate distribution within the seal

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Fig. 8

Friction factor: (a) rotor surface; (b) stator surface; and (c) between control volumes

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Fig. 6

Damper seal analytical model for determining the friction factor

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Fig. 9

Analytical model with multiple coordinate systems

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Fig. 10

Schematic of CFD model: (a) shape model and (b) final mesh

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Fig. 11

Forces acting on the rotor

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Fig. 14

Stability measurements: (a) N2 operation and (b) CO2 operation

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Fig. 15

Comparison of seal rotordynamic calculation results for CO2 operation at Ps = 6 MPa

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Fig. 12

Pressure distribution within the seal and distribution of swirl velocity



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