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Research Papers

Rim Seal Ingestion in a Turbine Stage From 360 Degree Time-Dependent Numerical Simulations

[+] Author and Article Information
Cheng-Zhang Wang

Pratt & Whitney,
East Hartford, CT 06108
e-mail: cheng-zhang.wang@pw.utc.com

Senthil Prasad Mathiyalagan

InfoTech Enterprises Limited,
Bangalore, India
e-mail: senthil.mathiyalagan@infotech-enterprises.com

Bruce V. Johnson

Pratt & Whitney/Independent Contractor,
Manchester, CT 06040
e-mail: bruce.v.johnson@att.net

J. Axel Glahn

e-mail: jorn.glahn@pw.utc.com

David F. Cloud

e-mail: david.cloud@pw.utc.com
Pratt & Whitney
East Hartford, CT 06108

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received March 1, 2013; final manuscript received May 16, 2013; published online September 26, 2013. Editor: David Wisler.

J. Turbomach 136(3), 031007 (Sep 26, 2013) (12 pages) Paper No: TURBO-13-1030; doi: 10.1115/1.4024684 History: Received March 01, 2013; Revised May 16, 2013

Numerical simulations of turbine rim seal experiments are conducted with a time-dependent, 360 deg computational fluid dynamics (CFD) model of the complete turbine stage with a rim seal and cavity to increase understanding of the rim seal ingestion physics. The turbine stage has 22 vanes and 28 blades and is modeled with a uniform flow upstream of the vane inlet, a pressure condition downstream of the blades, and three coolant flow conditions previously employed during experiments at Arizona State University. The simulations show the pressure fields downstream of the vanes and upstream of the blades interacting to form a complex pressure pattern above the rim seal. Circumferential distributions of 15 to 17 sets of ingress and egress velocities flow through the rim seal at the two modest coolant flow rate conditions. These flow distributions rotate at approximately wheel speed and are not equal to the numbers of blades or vanes. The seal velocity distribution for a high coolant flow rate with little or no ingestion into the stator wall boundary layer is associated with the blade pressure field. These pressure field characteristics and the rim seal ingress/egress pattern provide new insight to the physics of rim seal ingestion. Flow patterns within the rim cavity have large cells that rotate in the wheel direction at a slightly slower speed. These secondary flows are similar to structures noted in previous a 360 deg model and large sector models but not obtained in a single blade or vane sector model with periodic boundary condition at sector boundaries. The predictions of pressure profiles, sealing effectiveness, and cavity velocity components are compared with experimental data.

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References

Figures

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Fig. 1

Arizona State University rig geometry and instrumentation locations (C: concentration tap, P: pressure probe, T: thermocouple), from [3]; all dimensions in mm

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Fig. 2

The 360 deg CFD model with 28 blade and 22 vane segments

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Fig. 4

Time-dependent pressure at a monitor in gas path

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Fig. 5

Ingestion flow rates monitored at rim seal gap and inner-axial-seal gap at low purge flow condition, Cw = 1574

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Fig. 6

Gas-path pressure profiles at outer shroud and on the vane platform near the vane trailing edges for the low purge flow Cw = 1574 test condition

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Fig. 7

Overall flow fields in three numerical simulations. All views are taken from vanes to blades, with rotor rotating anticlockwise. (a) Pressure contours at various locations between blades and vanes at low purge flow condition Cw = 1574; (b) pressure contours at three purge flow levels near static wall; and (c) sealing effectiveness contours near static wall.

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Fig. 8

Radial velocity direction distributions at three radial locations in the cavity

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Fig. 9

Axial velocity ratio circumferential distributions for Cw = 1574 at the rim seal gap center location for four blade rotation moments, with and without a blade location shift in the plotting of the data

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Fig. 10

Axial velocity distributions at the rim seal gap for three purge flow conditions. Note: Vx > 0 indicates ingress; Vx < 0 indicates egress.

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Fig. 11

Tangential velocity and sealing effectiveness circumferential profiles at rim seal gap center location

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Fig. 12

Comparison of experimental data with CFD results in the x/s = 0.83 plane for the Cw = 1574 condition

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Fig. 13

Sealing effectiveness on the cavity static wall surface

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