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Research Papers

On-Line Temperature Measurement Inside a Thermal Barrier Sensor Coating During Engine Operation

[+] Author and Article Information
A. Yañez Gonzalez

Department of Mechanical Engineering,
Imperial College London,
London SW7 2AZ, UK
e-mail: a.yanez-gonzalez12@imperial.ac.uk

C. C. Pilgrim

Sensor Coating Systems Ltd.,
Imperial Incubator, Bessemer Building,
Level 1&2,
Imperial College London,
London SW7 2AZ, UK
e-mail: c.pilgrim@sensorcoatings.com

J. P. Feist

Sensor Coating Systems Ltd.,
Imperial Incubator, Bessemer Building,
Level 1&2,
Imperial College London,
London SW7 2AZ, UK
e-mail: j.feist@sensorcoatings.com

P. Y. Sollazzo

Sensor Coating Systems Ltd.,
Imperial Incubator, Bessemer Building,
Level 1&2,
Imperial College London,
London SW7 2AZ, UK
e-mail: p.sollazzo@stscience.com

F. Beyrau

Lehrstuhl für Technische Thermodynamik,
Otto-von-Guericke-Universität,
Magdeburg 39106, Germany
e-mail: frank.beyrau@ovgu.de

A. L. Heyes

School of Chemical and Process Engineering,
University of Leeds,
Leeds LS2 9JT, UK
e-mail: a.heyes@leeds.ac.uk

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received March 9, 2015; final manuscript received March 20, 2015; published online May 12, 2015. Assoc. Editor: Ronald Bunker.

J. Turbomach 137(10), 101004 (May 12, 2015) (9 pages) Paper No: TURBO-15-1042; doi: 10.1115/1.4030260 History: Received March 09, 2015

Existing thermal barrier coatings (TBCs) can be adapted enhancing their functionalities such that they not only protect critical components from hot gases but also can sense their own material temperature or other physical properties. The self-sensing capability is introduced by embedding optically active rare earth ions into the thermal barrier ceramic. When illuminated by light, the material starts to phosphoresce and the phosphorescence can provide in situ information on temperature, phase changes, corrosion, or erosion of the coating subject to the coating design. The integration of an on-line temperature detection system enables the full potential of TBCs to be realized due to improved accuracy in temperature measurement and early warning of degradation. This in turn will increase fuel efficiency and will reduce CO2 emissions. This paper reviews the previous implementation of such a measurement system into a Rolls-Royce jet engine using dysprosium doped yttrium-stabilized-zirconia (YSZ) as a single layer and a dual layer sensor coating material. The temperature measurements were carried out on cooled and uncooled components on a combustion chamber liner and on nozzle guide vanes (NGVs), respectively. The paper investigates the interpretation of those results looking at coating thickness effects and temperature gradients across the TBC. For the study, a specialized cyclic thermal gradient burner test rig was operated and instrumented using equivalent instrumentation to that used for the engine test. This unique rig enables the controlled heating of the coatings at different temperature regimes. A long-wavelength pyrometer was employed detecting the surface temperature of the coating in combination with the phosphorescence detector. A correction was applied to compensate for changes in emissivity using two methods. A thermocouple was used continuously measuring the substrate temperature of the sample. Typical gradients across the coating are less than 1 K/μm. As the excitation laser penetrates the coating, it generates phosphorescence from several locations throughout the coating and hence provides an integrated signal. The study successfully proved that the temperature indication from the phosphorescence coating remains between the surface and substrate temperature for all operating conditions. This demonstrates the possibility to measure inside the coating closer to the bond coat. The knowledge of the bond coat temperature is relevant to the growth of the thermally grown oxide (TGO) which is linked to the delamination of the coating and hence determines its life. Further, the data are related to a one-dimensional phosphorescence model determining the penetration depth of the laser and the emission.

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References

Figures

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Fig. 1

Micrograph of the Sensor TBC in as-sprayed condition on a test sample. Visible are substrate (bottom), bond coat (light gray) and sensor ceramic YSZ:Dy,Eu (top layer) (courtesy of the manufacturer).

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Fig. 2

Production line sensor TBC on NGV

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Fig. 3

Temperature reading Ts using the sensor TBC from a NGV under different operating conditions. T4 reflects the exhaust pipe temperature measured with a thermocouple. Error bars are multiplied by three for visibility.

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Fig. 4

A diagram of the test rig set up with the optical instrumentation

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Fig. 5

Calibration curve of YSZ:Dy sensor coating sample. The temperature ranges for the current study and the previous Viper test are indicated.

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Fig. 6

Temperature recording on the sample during emissivity calibrations on the hot plate

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Fig. 7

Temperature readings on the sample during calibration of the emissivity in the burner test rig with unstable flame conditions

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Fig. 8

Temperature recording for stable operating conditions in the burner test rig

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Fig. 9

Average temperatures read by the pyrometer, luminescence, and thermocouple, when the gradient is kept constant and the absolute temperatures increased. Also modeled results are included.

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Fig. 10

Average temperatures read by the pyrometer, luminescence, and thermocouple, when temperature is kept constant and the gradient is increased. Also, modeled results are included.

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