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Research Papers: Gas Turbines: Structures and Dynamics

Effects of Purge Flow Configuration on Sealing Effectiveness in a Rotor–Stator Cavity

[+] Author and Article Information
Kenneth Clark

Pratt & Whitney,
East Hartford, CT 06118
e-mail: kenneth.clark@pw.utc.com

Michael Barringer

Department of Mechanical and
Nuclear Engineering,
The Pennsylvania State University,
University Park, PA 16802
e-mail: mbarringer@psu.edu

David Johnson

Department of Mechanical and
Nuclear Engineering,
The Pennsylvania State University,
University Park, PA 16802
e-mail: dkj103@psu.edu

Karen Thole

Department of Mechanical and
Nuclear Engineering,
The Pennsylvania State University,
University Park, PA 16802
e-mail: KThole@psu.edu

Eric Grover

Pratt & Whitney,
East Hartford, CT 06118
e-mail: eric.grover@pw.utc.com

Christopher Robak

Pratt & Whitney,
East Hartford, CT 06118
e-mail: christopher.robak@pw.utc.com

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received April 15, 2018; final manuscript received May 13, 2018; published online July 12, 2018. Editor: David Wisler.

J. Eng. Gas Turbines Power 140(11), 112502 (Jul 12, 2018) (11 pages) Paper No: GTP-18-1169; doi: 10.1115/1.4040308 History: Received April 15, 2018; Revised May 13, 2018

Secondary air is bled from the compressor in a gas turbine engine to cool turbine components and seal the cavities between stages. Unsealed cavities can lead to hot gas ingestion, which can degrade critical components or, in extreme cases, can be catastrophic to engines. For this study, a 1.5 stage turbine with an engine-realistic rim seal was operated at an engine-relevant axial Reynolds number, rotational Reynolds number, and Mach number. Purge flow was introduced into the interstage cavity through distinct purge holes for two different configurations. This paper compares the two configurations over a range of purge flow rates. Sealing effectiveness measurements, deduced from the use of CO2 as a flow tracer, indicated that the sealing characteristics were improved by increasing the number of uniformly distributed purge holes and improved by increasing levels of purge flow. For the larger number of purge holes, a fully sealed cavity was possible, while for the smaller number of purge holes, a fully sealed cavity was not possible. For this representative cavity model, sealing effectiveness measurements were compared with a well-accepted orifice model derived from simplified cavity models. Sealing effectiveness levels at some locations within the cavity were well-predicted by the orifice model, but due to the complexity of the realistic rim seal and the purge flow delivery, the effectiveness levels at other locations were not well-predicted.

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References

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Figures

Grahic Jump Location
Fig. 1

START facility layout, which houses the 1.5 stage turbine

Grahic Jump Location
Fig. 2

1.5 stage turbine cross section: (a) first vane plenum, (b) front rim seal, (c) front rim cavity, (d) front wheel-space, (e) purge flow, (f) TOBI flow, and (g) aft rim cavity

Grahic Jump Location
Fig. 6

Static pressure normalized by the inlet total pressure on the vane trailing edge, the platform trailing edge (22% 1V axial chord downstream of vane trailing edge), and in the rim seal (8% 1V axial chord upstream of vane trailing edge) with no purge flow

Grahic Jump Location
Fig. 3

Turbine cross section with instrumentation locations. Effectiveness data will be presented for the following locations: (A) front rim seal, (B) outer radius of front rim cavity, (C) purge hole radius of front rim cavity, and (D) front wheel-space.

Grahic Jump Location
Fig. 4

Conditions in the turbine for a typical test

Grahic Jump Location
Fig. 5

Static pressure normalized by the vane inlet total pressure at 50% span for (a) first vane and (b) second vane

Grahic Jump Location
Fig. 7

Sealing effectiveness measurements for Configuration 1: 150 purge holes and Configuration 2: 32 purge holes

Grahic Jump Location
Fig. 8

Flow schematic of secondary flows in the 1.5 stage test turbine

Grahic Jump Location
Fig. 9

Schematic of flows in the rim cavity for the following configurations: (a) 150 purge holes at low flow rates, (b) 150 purge holes at high flow rates, (c) 32 purge holes at low flow rates, and (d) 32 purge holes at high flow rates

Grahic Jump Location
Fig. 10

Circumferential variation in concentration effectiveness for 32 purge holes

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Fig. 11

Empirical models for concentration effectiveness for 150 purge holes in terms of the net and minimum sealing flow rates, Φ* and Φmin

Grahic Jump Location
Fig. 12

Empirical models for concentration effectiveness for 32 purge holes in terms of the net and minimum sealing flow rates, Φ* and Φmin

Grahic Jump Location
Fig. 13

Comparison of several rim seals in terms of the empirically determined ratio of discharge coefficients, Γc

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