Research Papers

A Spectral Study of a Moderately Loaded Low-Pressure Turbine Airfoil—Part I: Identifying Frequencies Affecting Bypass Transition

[+] Author and Article Information
J. R. S. Graveline

Department of Mechanical and Aerospace Engineering,
Royal Military College of Canada,
Kingston, ON, K7K 7B4, Canada
e-mail: Sylvain.Graveline@rmc.ca

S. A. Sjolander

Department of Mechanical and Aerospace Engineering,
Carleton University,
Ottawa, ON, K1S 5B6, Canada
e-mail: ssjoland@mae.carleton.ca

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 12, 2012; final manuscript received July 26, 2012; published online June 5, 2013. Assoc. Editor: David Wisler.

J. Turbomach 135(4), 041016 (Jun 05, 2013) (11 pages) Paper No: TURBO-12-1141; doi: 10.1115/1.4007624 History: Received July 12, 2012; Revised July 26, 2012

A single wire, hot-wire, probe is used to examine the airflow in, and in close vicinity to, the shear layer of a low-pressure turbine (LPT) airfoil. A spectral analysis of the data identifies two sets of wide peaks of turbulent kinetic energy, one near 200 Hz and a second near 1 kHz. A method is developed to identify these peaks based on a combination of empirical relations between the airflow velocity and boundary layer thickness and on the location of the frequency peaks relative to the state of the free shear layer as it transitioned from laminar to turbulent. The method suggests the presence of Tollmien–Schlichting waves and Kelvin–Helmholtz instabilities. The Kelvin–Helmholtz instabilities are shown to pair.

Copyright © 2013 by ASME
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Fig. 1

Carleton low-speed linear-cascade wind tunnel (reproduced from Mahallati [9])

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Fig. 2

Identification of separation bubble using the pressure gradient approach

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Fig. 3

Locations of pressure taps and hotwire measurements

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Fig. 4

Location of hotwire measurements for time domain analyses—circles show locations where energy spectra are presented

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Fig. 5

Sample energy spectra measurements in a separation bubble: (a) velocity fluctuations, (b) energy spectra below maximum velocity fluctuation location, and (c) energy spectra above maximum velocity fluctuation location

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Fig. 6

Energy spectra of singlewire probe measurements at the most upstream station

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Fig. 7

Energy spectra of singlewire probe measurements at a streamwise station in the separation bubble (ξ/SSL = 0.66)

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Fig. 8

Energy spectra of singlewire probe measurements at the location of maximum bubble thickness (ξ/SSL = 0.71)

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Fig. 9

Energy spectra of singlewire probe measurements near reattachment (ξ/SSL = 0.76)

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Fig. 10

Energy spectra of singlewire probe data reattached station ξ/SSL = 0.86

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Fig. 11

Energy spectra of singlewire probe measurements at reattached station ξ/SSL = 0.92

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Fig. 12

Methodology to determine the strength in spectral peaks—measurements taken at ξ/SSL = 0.76

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Fig. 13

Flood of the strength of the TS peaks

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Fig. 14

Flood of the strength of the KH peaks

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Fig. 15

Flood of the frequencies associated with the TS peaks

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Fig. 16

Frequency associated with KH peaks




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