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Research Papers: Gas Turbines: Structures and Dynamics

Design of Experiments to Investigate Geometric Effects on Fluid Leakage Rate in a Balance Drum Seal

[+] Author and Article Information
Neal R. Morgan

Rotating Machinery
and Controls (ROMAC) Laboratory,
Department of Mechanical
and Aerospace Engineering,
University of Virginia,
122 Engineer's Way,
Charlottesville, VA 22904-4746
e-mail: nrm6dr@virginia.edu

Alexandrina Untaroiu

Rotating Machinery
and Controls (ROMAC) Laboratory,
Department of Mechanical
and Aerospace Engineering,
University of Virginia,
122 Engineer's Way,
Charlottesville, VA 22904-4746
e-mail: au6d@virginia.edu

Patrick J. Migliorini

Rotating Machinery
and Controls (ROMAC) Laboratory,
Department of Mechanical
and Aerospace Engineering,
University of Virginia,
122 Engineer's Way,
Charlottesville, VA 22904-4746
e-mail: pjm5b@virginia.edu

Houston G. Wood

Rotating Machinery
and Controls (ROMAC) Laboratory,
Department of Mechanical
and Aerospace Engineering,
University of Virginia,
122 Engineer's Way,
Charlottesville, VI 22904-4746
e-mail: hgw9p@virginia.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 9, 2014; final manuscript received July 18, 2014; published online September 30, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(3), 032501 (Sep 30, 2014) (7 pages) Paper No: GTP-14-1354; doi: 10.1115/1.4028382 History: Received July 09, 2014; Revised July 18, 2014

Annular labyrinth seals are designed as tortuous paths that force a working fluid to expand and contract repeatedly through small clearances between high and low pressure stages of turbomachinery. The resulting expansion and recirculation reduces kinetic energy of the flow and minimizes leakage rate between regions of high and low pressure through the seal. Most current seal geometries are selected based on what has worked in the past, or by incremental improvements on existing designs. In the present research, a balance drum used in a multistage centrifugal pump was chosen as a starting point. A design of experiments (DOEs) study was performed to investigate the influence of groove scale on leakage rate across the seal for a fixed pressure differential. The computational fluid dynamics (CFD) model of the selected labyrinth seal has an upstream region leading to 20 evenly spaced semicircular grooves along a 267 mm seal length, with a clearance region of 0.305 mm. The seal geometry was specified by a set of five variables. The variables allow for variation in scale of the semicircular grooves within a pattern of five independently scaled grooves repeated four times along the seal length. The seal was constructed with a parameterized CFD model in ansys-CFX as a 5 deg sector of the full 3D seal. A noncentral composite designed experiment was performed to investigate the effects of five parameters on leakage rate in the system. This study demonstrates a practical approach for investigating the effects of various geometric factors on leakage rate for balance drum seals. The empirical ten-parameter linear regression model fitted to the results of the experimental design yields suggested groove radii that could be applied to improve performance of future seals.

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Figures

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Fig. 1

23 Factorial design

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Fig. 2

Central composite design in two factors

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Fig. 3

Base seal geometry, a 5 deg sector of the full seal

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Fig. 4

Parameterization of seal geometry

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Fig. 6

Pressure profile mesh dependence

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Fig. 7

Axial velocity profile mesh dependence

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Fig. 8

Pareto chart estimated by sum of squares

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Fig. 9

Residuals versus predicted response

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Fig. 10

Predicted versus actual response

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Fig. 11

Response surface of mass flow rate versus R1 and R2

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Fig. 12

Response surface of mass flow rate versus R1 and R3

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Fig. 13

Design point geometry for predicted optimal leakage rate

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Fig. 14

Radii of grooves for base model (left) versus optimal design point (right)

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