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Research Papers

Performance of a Finned Turbine Rim Seal

[+] Author and Article Information
Carl M. Sangan

Department of Mechanical Engineering,
University of Bath,
Bath BA2 7AY, UK
e-mail: c.m.sangan@bath.ac.uk

James A. Scobie, J. Michael Owen, Gary D. Lock

Department of Mechanical Engineering,
University of Bath,
Bath BA2 7AY, UK

Kok Mun Tham

Siemens Energy, Inc.,
Fossil Power Generation,
Orlando, FL 32828

Vincent P. Laurello

Siemens Energy, Inc.,
Fossil Power Generation,
Jupiter, FL 33458

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 21, 2014; final manuscript received July 25, 2014; published online August 26, 2014. Editor: Ronald Bunker.

J. Turbomach 136(11), 111008 (Aug 26, 2014) (10 pages) Paper No: TURBO-14-1162; doi: 10.1115/1.4028116 History: Received July 21, 2014; Revised July 25, 2014

In gas turbines, rim seals are fitted at the periphery of the wheel-space between the turbine disk and its adjacent casing; their purpose is to reduce the ingress of hot mainstream gases. A superposed sealant flow, bled from the compressor, is used to purge the wheel-space or at least dilute the ingress to an acceptable level. The ingress is caused by the circumferential variation of pressure in the turbine annulus radially outward of the seal. Engine designers often use double-rim seals where the variation in pressure is attenuated in the outer wheel-space between the two seals. This paper describes experimental results from a research facility that models an axial turbine stage with engine-representative rim seals. The radial variation of CO2 gas concentration, swirl, and pressure, in both the inner and outer wheel-space, are presented over a range of purge flow rates. The data are used to assess the performance of two seals: a datum double-rim seal and a derivative with a series of radial fins. The concept behind the finned seal is that the radial fins increase the swirl in the outer wheel-space; measurements of swirl show the captive fluid between the fins rotate with near solid body rotation. The improved attenuation of the pressure asymmetry, which governs the ingress, results in an improved performance of the inner geometry of the seal. The fins also increased the pressure in the outer wheel-space and reduced the ingress though the outer geometry of the seal.

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References

Figures

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Fig. 1

Generic rotor–stator turbine stage and typical rim-seal (inset)

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Fig. 2

Variation of static pressure in a turbine annulus. Regions of high and low pressure with respect to the wheel-space are indicated accordingly. For the double-rim seal shown, the pressure asymmetry is attenuated in the outer wheel-space between the two seal clearances.

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Fig. 3

Comparison between theoretical effectiveness and experimental data for radial-clearance seal S [5] (symbols denote data; lines are theoretical curves)

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Fig. 4

Rig test section highlighting pressure instrumentation and typical pressure asymmetry in the annulus (inset)

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Fig. 5

Rim seal configurations (in DF, fins shown shaded)

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Fig. 6

Geometry of finned-rim seal

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Fig. 7

Variation of εc with Φo for seals D and DF (symbols denote data; lines are theoretical curves)

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Fig. 8

Seal performance ranking shown in order of magnitude of Φmin* for double radial-clearance seals and the baseline configuration

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Fig. 9

Effect of sealing flow rate on measured radial variation of effectiveness for seals D and DF. Open symbols denote D; shaded symbols denote DF.

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Fig. 10

Radial distribution of swirl ratio for datum double seal (D) and finned-rim seal (DF) for different λT at Reϕ = 8.2 × 105

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Fig. 11

Radial distribution of swirl ratio and pressure coefficient (static) for seals D and DF. Symbols denote measured values; lines denote fitted distribution for β and calculated distribution for Cp.

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