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Research Papers

Hot Streak and Vane Coolant Migration in a Downstream Rotor

[+] Author and Article Information
Jonathan Ong1

Robert J. Miller

 Whittle Laboratory,  University of Cambridge, 1 JJ Thomson Avenue, Cambridge, CB3 0DY, England

1

Corresponding author. Current address: GE Global Research, Freisinger Landstrasse 50, D-85748 Garching bei München, Germany.

J. Turbomach 134(5), 051002 (May 07, 2012) (10 pages) doi:10.1115/1.4003832 History: Received January 07, 2011; Revised January 08, 2011; Published May 07, 2012; Online May 07, 2012

This paper describes a method of improving the cooling of the hub region of high-pressure turbine (HPT) rotor by making better use of the unsteady coolant flows originating from the upstream vane. The study was performed computationally on an engine HPT stage with representative inlet hot streak and vane coolant conditions. An experimental validation study of hot streak migration was undertaken on two low-speed test facilities. The unsteady mechanisms that transport hot and cold fluid within the rotor hub region are first examined. It was found that vortex-blade interaction dominated the unsteady transport of hot and cold fluid in the rotor hub region. This resulted in the transport of hot fluid onto the rotor hub and pressure surface, causing a peak in the surface gas temperatures. The vane film coolant was found to have only a limited effect in cooling this region. A new cooling configuration was thus examined which exploits the unsteadiness in rotor hub to aid transport of coolant towards regions of high rotor surface temperatures. The new coolant was introduced from a slot upstream of the vane. This resulted in the feed of slot coolant at a different phase and location relative to the vane film coolant within the rotor. The slot coolant was entrained into the unsteady rotor secondary flows and transported towards the rotor hub-pressure surface region. The slot coolant reduced the peak time-averaged rotor temperatures by a similar amount as the vane film coolant despite having only a sixth of the coolant mass flow.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 3

Simplified rotor flow structure as observed from an axial slice through a rotor subject to a shed vortex and hot streak

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Figure 4

Hot streak injection on the duct and measured temperature distributions

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Figure 5

Effect of free stream turbulence on temperature distributions

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Figure 6

LSRT Hot streak injection

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Figure 7

LSRT Instantaneous temperature distribution

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Figure 8

Comparison between measured and predicted hot streak distributions at (a) vane exit and (b) rotor exit of the LSRT (contour interval = 2 K)

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Figure 9

HPT stage inlet temperature distribution

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Figure 10

Vane exit (a) stagnation temperature and (b) streamwise vorticity distribution (baseline cooling configuration)

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Figure 11

Transport of hot and cold fluid at midspan

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Figure 12

Unsteady secondary flow vectors and temperature redistribution at 75% rotor Cx

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Figure 13

Time-averaged unsteady and steady relative stagnation temperature distributions at 75% Cx with (a) all vanes cooled (baseline), (b) only hot vanes cooled, (c) no vanes cooled

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Figure 14

Injection of coolant from slot upstream of the vane and predicted streamline pattern

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Figure 15

Vane exit (a) stagnation temperature and (b) streamwise vorticity distribution. With inlet slot coolant injection and all vanes cooled.

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Figure 16

Time resolved migration of slot coolant at 75% CX (difference from baseline configuration plotted)

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Figure 17

Selection of two rotor zones in baseline cooling configuration

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Figure 18

Effect of vane coolant injection on average temperature in zones 1 and 2 (steady and unsteady computations)

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Figure 1

General arrangement of combustor and HPT on a Mitsubishi F class engine [1]

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Figure 2

Formation of ‘hairpin structures’ with counter rotating legs within a rotor passage (shown up to 50% span for clarity)

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