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Research Papers

Experimental Measurements of Ingestion Through Turbine Rim Seals—Part I: Externally Induced Ingress

[+] Author and Article Information
Oliver J. Pountney, Gary D. Lock

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

Kunyuan Zhou

Department of Engineering Thermophysics,
School of Jet Propulsion,
Beihang University,
Beijing, 100191, PRC

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received October 14, 2011; final manuscript received October 27, 2011; published online November 8, 2012. Editor: David Wisler.

J. Turbomach 135(2), 021012 (Nov 08, 2012) (10 pages) Paper No: TURBO-11-1229; doi: 10.1115/1.4006609 History: Received October 14, 2011; Revised October 27, 2011

This paper describes a new research facility which experimentally models hot gas ingestion into the wheel-space of an axial turbine stage. Measurements of the CO2 gas concentration in the rim-seal region and inside the cavity are used to assess the performance of two generic (though engine-representative) rim-seal geometries in terms of the variation of concentration effectiveness with sealing flow rate. The variation of pressure in the turbine annulus, which governs this externally-induced (EI) ingestion, was obtained from steady pressure measurements downstream of the vanes and near the rim seal upstream of the rotating blades. Although the ingestion through the rim seal is a consequence of an unsteady, three-dimensional flow field and the cause-effect relationship between the pressure and the sealing effectiveness is complex, the experimental data is shown to be successfully calculated by simple effectiveness equations developed from a previously published orifice model. The data illustrate that, for similar turbine-stage velocity triangles, the effectiveness can be correlated using a nondimensional sealing parameter, Φo. In principle, and within the limits of dimensional similitude, these correlations should apply to a geometrically-similar engine at the same operating conditions. Part II of this paper describes an experimental investigation of rotationally-induced (RI) ingress, where there is no mainstream flow and consequently no circumferential variation of external pressure.

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References

Figures

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Fig. 1

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

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Fig. 2

Variation of static pressure in a turbine annulus. Red arrows indicate hot-gas ingress and blue arrows indicate cooler egress, corresponding to regions of high and low pressure with respect to the wheel-space, respectively.

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Fig. 3

implified diagram of ingress and egress (a) Φ0 < Φmin (b) Φ0 =  Φmin

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Fig. 4

(a) Rig test section showing turbine stage, and (b) rig test section showing sealing and mainstream flows (red, stationary; blue, rotating)

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Fig. 8

(a) Effect of ReΦ on the circumferential distribution of Cp over the nondimensional vane pitch (Rew/Reφ) = 0.6. (b) Effect of Φ0min,EI on the circumferential distribution of Cp over the nondimensional vane pitch Reφ = 8.17 × 105 (Rew/Reφ) = 0.6. (c) Effect of Reφ on variation of ΔCp1/2 with ReW/Reφ at locations A and B in annulus.

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Fig. 7

Generic vane and blade geometry and associated velocity triangles

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Fig. 6

Radial displacement of radial-clearance seal measured at the seal-tip

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Fig. 5

(a) Left: simple axial-clearance seal, and (b) right: generic radial-clearance seal

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Fig. 9

(a) Effect of Reφ on measured variation of ɛc with Cw,o for both tested rim seals. (Open symbols denote radial-clearance seal; solid symbols denote axial-clearance seal.) (b) Variation of Cw,min with Cp,max1/2 ReW, highlighting seal comparisons using K.

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Fig. 10

(a) Measured variation of sealing effectiveness with Φ0 for EI ingress for (Rew/Reφ) = 0.538 (open symbols denote radial-clearance seal; solid symbols denote axial-clearance seal). (b) Comparison between theoretical effectiveness curves and experimental data for axial-clearance seal with EI ingress for (Rew/Reφ) = 0.538 (open symbols denote ɛ data; closed symbols denote Φi,EI/Φmin,EI data; solid lines are theoretical curves). (c) Comparison between theoretical effectiveness curves and experimental data for radial-clearance seal with the EI ingress for (Rew/Reφ) = 0.538 (open symbols denote ɛ data; closed symbols denote Φi,EI/Φmin,EI data; solid lines are theoretical curves).

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