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Research Papers: Gas Turbines: Controls, Diagnostics, and Instrumentation

An Improved Nickel Based MIMS Thermocouple for High Temperature Gas Turbine Applications

[+] Author and Article Information
Michele Scervini

e-mail: ms737@cam.ac.uk

Catherine Rae

e-mail: cr18@cam.ac.uk
Department of Materials Science and Metallurgy,
University of Cambridge,
Pembroke Street,
Cambridge CB2 3QZ, UK

A second alternative to the bare wire Type K thermocouple is the Platinel thermocouple, which is based on the Pt-Pd system and is less affected by oxidation than Type K thermocouple. It is used in bare wire configuration only in military engines (T56 turboprop), due to its high cost.

1Corresponding author.

Contributed by the Controls, Diagnostics and Instrumentation Committee of ASME for publication in the Journal of Engineering for Gas Turbines and Power. Manuscript received March 9, 2013; final manuscript received April 30, 2013; published online July 31, 2013. Editor: David Wisler.

J. Eng. Gas Turbines Power 135(9), 091601 (Jul 31, 2013) (6 pages) Paper No: GTP-13-1075; doi: 10.1115/1.4024420 History: Received March 09, 2013; Revised April 30, 2013

A new nickel based thermocouple for high temperature applications in gas turbines has been devised at the Department of Material Science and Metallurgy of the University of Cambridge. This paper describes the new features of the thermocouple, the drift tests on the first prototype, and compares the behavior of the new sensor with conventional mineral insulated metal sheathed Type K thermocouples: the new thermocouple has a significant improvement in terms of drift and temperature capabilities. Metallurgical analysis has been undertaken on selected sections of the thermocouples exposed at high temperatures, which rationalizes the reduced drift of the new sensor. A second prototype will be tested in subsequent research, from which further improvements in drift and temperature capabilities are expected.

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References

Cumpsty, N., 2003, Jet Propulsion, Cambridge University Press, Cambridge, UK.
HEATTOP Project, Work Package 1, 2007, “Definitions and Sensor Specifications.”
EVI-GTI, 2010, “European Virtual Institute for Gas Turbine Instrumentation,” www.evi-gti.com.
Gatward, W. A., 1935, “Chromel and Alumel; Alloys for Thermocouples,” Met. Prog., 27, pp. 31–35.
ASTM, 1993, “Manual on the Use of Thermocouple in Temperature Measurement,” American Society for Testing Materials, Philadelphia.
Burley, N. A., 1969, “Solute Depletion and Thermo-e.m.f. Drift in Nickel-Base Thermocouple Alloys,” J. Inst. Met., 97, pp. 252–254.
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Anderson, R. L., Lyons, J. D., Kollie, T. G., Christie, W. H., and Eby, R., 1982, “Decalibration of Sheathed Thermocouples,” Temperature: Its Measurement and Control in Science and Industry, Vol. 5, American Institute of Physics, New York, pp. 977–1007.
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Potts, J. F., and McElroy, D. L., 1962, “The Effects of Cold Working, Heat Treatment, and Oxidation on the Thermal EMF of Nickel-Base ThermoElements,” Temperature: Its Measurement and Control in Science and Industry, Vol. 3, American Institute of Physics, New York, pp. 243–264.
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Figures

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Fig. 1

Schematic diagram of a two-shaft gas turbine

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Fig. 2

Bare wire thermocouple

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Fig. 3

MIMS configuration; schematic longitudinal and cross sections

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Fig. 4

Schematic diagram of the instrumentation used for measuring the thermocouple voltage

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Fig. 5

A cross section diagram of the new thermocouple

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Fig. 6

X-ray image of the longitudinal section of the prototype (courtesy of Meggitt PLC)

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Fig. 7

Drift of Pt versus KN thermocouple

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Fig. 8

Drift of KP versus Pt thermocouple

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Fig. 9

Mn content in the KN thermo-element; the cross section experienced 1200 °C for 400 h

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Fig. 10

Cr content in the KN thermo-element; the cross section experienced 1200 °C for 400 h

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Fig. 11

Mn content in the KP thermo-element; the cross section experienced 1200 °C for 400 h

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