Research Papers: Gas Turbines: Structures and Dynamics

Effect of Ingress on Turbine Disks

[+] Author and Article Information
GeonHwan Cho

Department of Mechanical Engineering,
University of Bath,
Bath BA2 7AY, UK
e-mail: g.h.cho@bath.ac.uk

Carl M. Sangan, J. Michael Owen, Gary D. Lock

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

1Corresponding author.

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 14, 2015; final manuscript received July 21, 2015; published online October 13, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 138(4), 042502 (Oct 13, 2015) (10 pages) Paper No: GTP-15-1293; doi: 10.1115/1.4031436 History: Received July 14, 2015; Revised July 21, 2015

The ingress of hot gas through the rim seal of a gas turbine depends on the pressure difference between the mainstream flow in the turbine annulus and that in the wheel-space radially inward of the seal. This paper describes experimental measurements which quantify the effect of ingress on both the stator and rotor disks in a wheel-space pressurized by sealing flow. Infrared (IR) sensors were developed and calibrated to accurately measure the temperature history of the rotating disk surface during a transient experiment, leading to an adiabatic effectiveness. The performance of four generic (though engine-representative) single- and double-clearance seals was assessed in terms of the variation of adiabatic effectiveness with sealing flow rate. The measurements identify a so-called thermal buffering effect, where the boundary layer on the rotor protects the disk from the effects of ingress. It was shown that the effectiveness on the rotor was significantly higher than the equivalent stator effectiveness for all rim seals tested. Although the ingress through the rim seal is a consequence of an unsteady, three-dimensional flow field, and the cause–effect relationship between pressure and the sealing effectiveness is complex, the time-averaged experimental data are shown to be successfully predicted by relatively simple semi-empirical models, which are described in a separate paper. Of particular interest to the designer, significant ingress can enter the wheel-space before its effect is sensed by the rotor.

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Fig. 1

(a) Typical high-pressure gas-turbine stage and (b)details of rim seal

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Fig. 2

Simplified diagram of ingress and egress, showing boundary layers on the stator and rotor

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Fig. 3

IR sensor assembly

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Fig. 4

Calibration wind tunnel featuring composite substrate target plate (inset)

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Fig. 5

Typical calibration curve of an IR sensor for both the steady-state (large open circles) and transient conditions (∼103 discrete black data points)

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Fig. 6

Variation of heat flux with wall temperature for a typical experiment

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Fig. 7

Variation of boundary layer thickness (δ) at x = 185 mm and heat transfer coefficient (h) at x = 200 mm with Reynolds number (lines are empirical correlations)

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Fig. 8

Test section showing instrumentation in the wheel-space (red/background—stationary and blue/foreground—rotating)

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Fig. 9

Rim-seal configurations

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Fig. 10

Effect of sealing flow rate on measured radial variation of effectiveness for single radial-clearance seal S2

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Fig. 11

Effect of sealing flow rate on measured radial variation of effectiveness for double radial-clearance seal D2

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Fig. 12

Typical nondimensional surface and core temperature history with and without ingress

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Fig. 13

Variation of effectiveness with nondimensional sealing flow rate for single seals (symbols denote data; lines are theoretical curves [6,13])

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Fig. 14

Variation of effectiveness with nondimensional sealing flow rate for double seals (symbols denote data; lines are theoretical curves [6,13])




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