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Research Papers

Comparison of Heat Transfer Measurement Techniques on a Transonic Turbine Blade Tip

[+] Author and Article Information
D. O. O’Dowd, Q. Zhang, L. He, P. M. Ligrani

Department of Engineering, University of Oxford, Parks Road, Oxford OX1 3PJ, UK

S. Friedrichs

 Rolls-Royce plc, P.O. Box 31, Moor Lane, Derby DE24 8BJ, UK

J. Turbomach 133(2), 021028 (Oct 27, 2010) (10 pages) doi:10.1115/1.4001236 History: Received September 01, 2009; Revised September 30, 2009; Published October 27, 2010; Online October 27, 2010

The present study considers spatially resolved surface heat transfer coefficients and adiabatic wall temperatures on a turbine blade tip in a linear cascade under transonic conditions. Five different measurement and processing techniques using infrared thermography are considered and compared. Three transient methods use the same experimental setup, using a heater mesh to provide a near-instantaneous step-change in mainstream temperature, employing an infrared camera to measure surface temperature. These three methods use the same data but different processing techniques to determine the heat transfer coefficients and adiabatic wall temperatures. Two of these methods use different processing techniques to reconstruct heat flux from the temperature time trace measured. A plot of the heat flux versus temperature is used to determine the heat transfer coefficients and adiabatic wall temperatures. The third uses the classical solution to the 1D nonsteady Fourier equation to determine heat transfer coefficients and adiabatic wall temperatures. The fourth method uses regression analysis to calculate detailed heat transfer coefficients for a quasi-steady-state condition using a thin-foil heater on the tip surface. Finally, the fifth method uses the infrared camera to measure the adiabatic wall temperature surface distribution of a blade tip after a quasi-steady-state condition is present. Overall, the present study shows that the infrared thermography technique with heat flux reconstruction using the impulse method is the most accurate, computationally efficient, and reliable method to obtain detailed, spatially resolved heat transfer coefficients and adiabatic wall temperatures on a transonic turbine blade tip in a linear cascade.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Seventeen heat transfer gauges positioned along the mean camber line (from Thorpe (8))

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Figure 2

University of Oxford high-speed linear cascade

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Figure 3

The schematic of the test section and instrumentation

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Figure 4

HSLC inlet conditions for 90 s run. Steady conditions achieved after 10 s for inlet total pressure.

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Figure 5

Mach number distribution around the blade

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Figure 6

IR camera calibration

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Figure 7

Penetration depth analysis at leading edge with 10 mm depth, for heat transfer coefficient of 2000 W/m2 K, at various times during the test

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Figure 8

Contours of (a) heat transfer coefficient (W/m2 K) and (b) adiabatic wall temperature (°C) using Method A-1, idealized process approach

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Figure 9

An example of heat flux versus temperature history after the heater mesh is turned on

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Figure 10

Contours of (a) heat transfer coefficient (W/m2 K) and (b) adiabatic wall temperature (°C) using Method A-2, finite-difference heat flux reconstruction method

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Figure 11

Contours of (a) heat transfer coefficient (W/m2 K) and (b) adiabatic wall temperature (°C) using Method A-3, heat flux reconstruction method using impulse technique

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Figure 12

Thin-foil heater employed in the present study

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Figure 13

Temperature history of the mainstream and blade tip after the thin-foil heater is on

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Figure 14

Heat flux versus temperature for four sets of experimental data using a thin-foil heater

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Figure 15

Contours of (a) heat transfer coefficient (W/m2 K) and (b) adiabatic wall temperature (°C) using Method B, thin-foil heater

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Figure 16

Contour of the adiabatic wall temperature (°C) using Method C, quasi-adiabatic. The very last snapshot of tip temperature distribution after the heater mesh is turned on for 20 s.

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Figure 17

Heat transfer technique repeatability indicating fraction difference between heat transfer coefficient for three experimental runs (local standard deviation divided by area-weighted mean value) for (a) Method A-3, impulse method and (b) Method A-1, idealized process

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Figure 18

Heat transfer technique repeatability indicating standard deviation of adiabatic wall temperature (K) for three experimental runs for (a) Method A-3, impulse method and (b) Method A-1, idealized process

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Figure 19

Circumferential averaged transient thermal measurement calculations on the tip (axial-chordwise averages): (a) heat transfer coefficient and (b) adiabatic wall temperature

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