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Research Papers

Main Gas Ingestion in a Turbine Stage for Three Rim Cavity Configurations

[+] Author and Article Information
D. W. Zhou, R. P. Roy

Department of Mechanical and Aerospace Engineering, Arizona State University, Tempe, AZ 85287

C.-Z. Wang, J. A. Glahn

 Pratt and Whitney, East Hartford, CT 06118

J. Turbomach 133(3), 031023 (Dec 07, 2010) (12 pages) doi:10.1115/1.4002423 History: Received February 07, 2010; Revised February 22, 2010; Published December 07, 2010; Online December 07, 2010

Experiments were carried out in a model air turbine stage to study the influence of rotor-stator rim cavity configuration on the ingestion of mainstream gas into the cavity. The three rim cavity configurations differed in their aspect ratio (height/width); the rim seal geometry remained the same. The aspect ratio was changed from the baseline ratio by installing an inner shell on the stator at an appropriate radius; this effectively introduced an axial-gap seal between the rim cavity and the cavity radially inboard. The initial step in each experiment was the measurement of time-average static pressure distribution in the turbine stage to ascertain that proper flow condition had been established. Subsequently, tracer gas concentration and particle image velocimetry techniques were employed to measure the time-average but spatially local main gas ingestion and the instantaneous velocity field in the rim cavity. At low purge air flow, regions of ingestion and egress could be identified by inspecting the instantaneous radial velocity distribution near the rim seal obtained from cavity gas velocity maps close to the stator. While the tangential velocity tended to be slightly larger for the so determined ingested gas, a more clear-cut indicator of ingestion was the strong inward gas radial velocity. Information provided by ensemble-average velocity maps was not sufficient for identifying ingestion because the averaging smeared out flow details, which varied from instant to instant. Velocity fields obtained from three-dimensional, time-dependent numerical simulation of a rim seal-cavity sector with similar dimensions qualitatively showed similar characteristics in the outer part of the cavity and provided insight into the complex flow in the seal region.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Schematic diagram of the single-stage turbine with three different rim cavity configurations (C: concentration tap, P: static pressure tap, T: thermocouple; all dimensions are in mm)

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Figure 2

The 1/25-stage sector model for configuration 3

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Figure 3

Sealing effectiveness at one monitoring point

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Figure 4

Instantaneous images obtained near the stator at x/s=0.830 for Revax=1.12×105, Reϕ=5.86×105, and cw=1574 (expt. set I)

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Figure 5

Comparison of dimensionless velocity ratios near the stator at x/s=0.83 from instantaneous images for Revax=1.12×105, Reϕ=5.86×105, and cw=1574 (expt. set I)

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Figure 6

Instantaneous images obtained near the stator at x/s=0.830 for Revax=9.27×104, Reϕ=4.63×105, and cw=1574 (expt. set II)

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Figure 7

Comparison of dimensionless velocity ratios near the stator at x/s=0.830 from instantaneous images for Revax=9.27×104, Reϕ=4.63×105, and cw=1574 (expt. set II)

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Figure 8

Comparison of dimensionless velocity ratios for the three rim cavity configurations from instantaneous images near the rotor (5 mm) for Revax=1.12×105, Reϕ=5.86×105, and cw=1574 (expt. set I)

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Figure 9

Comparison of local sealing effectiveness at the stator surface at two rotor speeds and main air flow rates

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Figure 10

Axial distributions of sealing effectiveness in the rim cavity

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Figure 11

Instantaneous image for configuration 2 obtained near the stator at x/s=0.830−Revax=1.12×105, Reϕ=5.86×105, and cw=8656 (expt. set I)

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Figure 12

Dimensionless velocity ratios for configuration 2 near the stator at x/s=0.830−Revax=1.12×105, Reϕ=5.86×105, and cw=8656 (expt. set I)

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Figure 13

Comparison of local sealing effectiveness at the stator surface for the expt. sets I and II at cw=8656

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Figure 14

Ensemble-average image for configuration 2 obtained near the stator at x/s=0.830 for Revax=1.12×105, Reϕ=5.86×105, and cw=1574 (expt. set I)

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Figure 15

Comparison of dimensionless velocity ratios from Fig. 1—ensemble-average image for configuration 2 near the stator at x/s=0.830 for Revax=1.12×105, Reϕ=5.86×105, and cw=1574 (expt. set I)

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Figure 16

Comparison of experimental data with CFD results, configuration 3—dimensionless radial and tangential velocity ratios near the stator at x/s=0.830 for Revax=1.12×105, Reϕ=5.86×105, and cw=1574 (expt. set I)

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Figure 17

Sealing effectiveness at the stator surface for configuration 3 at Revax=1.12×105, Reϕ=5.86×105, and cw=1574 (expt. set I)—comparison between experiments and CFD simulation

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