Research Papers: Gas Turbines: Manufacturing, Materials, and Metallurgy

Application of an Industrial Sensor Coating System on a Rolls-Royce Jet Engine for Temperature Detection

[+] Author and Article Information
S. Berthier

Southside Thermal Sciences,
London, United Kingdom

B. Charnley

Cranfield University,
Cranfield, United Kingdom

J. Wells

RWE npower,
Swindon, United Kingdom

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 9, 2012; final manuscript received July 9, 2012; published online November 21, 2012. Editor: Dilip R. Ballal.

J. Eng. Gas Turbines Power 135(1), 012101 (Nov 21, 2012) (9 pages) Paper No: GTP-12-1262; doi: 10.1115/1.4007370 History: Received July 09, 2012; Revised July 09, 2012

Thermal barrier coatings are used to reduce the actual working temperature of the high pressure turbine blade metal surface and; hence permit the engine to operate at higher more efficient temperatures. Sensor coatings are an adaptation of existing thermal barrier coatings to enhance their functionality, such that they not only protect engine components from the high temperature gas, but can also measure the material temperature accurately and determine the health of the coating e.g., ageing, erosion and corrosion. The sensing capability is introduced by embedding optically active materials into the thermal barrier coatings and by illuminating these coatings with excitation light phosphorescence can be observed. The phosphorescence carries temperature and structural information about the coating. Accurate temperature measurements in the engine hot section would eliminate some of the conservative margins which currently need to be imposed to permit safe operation. A 50 K underestimation at high operating temperatures can lead to significant premature failure of the protective coating and loss of integrity. Knowledge of the exact temperature could enable the adaptation of the most efficient coating strategies using the minimum amount of air. The integration of an on-line temperature detection system would enable the full potential of thermal barrier coatings to be realized due to improved accuracy in temperature measurement and early warning of degradation. This, in turn, will increase fuel efficiency and reduce CO2 emissions. Application: This paper describes the implementation of a sensor coating system on a Rolls-Royce jet engine. The system consists of three components: industrially manufactured robust coatings, advanced remote detection optics and improved control and readout software. The majority of coatings were based on yttria stabilized zirconia doped with Dy (dysprosium) and Eu (europium), although other coatings made of yttrium aluminum garnet were manufactured as well. Coatings were produced on a production line using atmospheric plasma spraying. Parallel tests at Didcot power station revealed survivability of specific coatings in excess of 4500 effective operating hours. It is deduced that the capability of these coatings is in the range of normal maintenance schedules of industrial gas turbines of 24,000 h or even longer. An advanced optical system was designed and manufactured permitting easy scanning of coated components and also the detection of phosphorescence on rotating turbine blades (13 k rotations per minute) at stand-off distances of up to 400 mm. Successful temperature measurements were taken from the nozzle guide vanes (hot), the combustion chamber (noisy) and the rotating turbine blades (moving) and compared with thermocouple and pyrometer installations for validation purposes.

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Fig. 1

Example of an MCrAlY + APS TBC coating system on a large industrial gas turbine component

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Fig. 2

Optical microscope image showing the microstructure of the top 3 layers of coating achieved for the STS mix coating for the blade qualification (from the manufacturer coating qualification report)

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Fig. 3

Illustration of the optical probe

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Fig. 4

OPETS FOV. The positions A, B, C are equivalent to the positions in Fig. 3. The flat hat function permits undistorted detection across a wide FOV.

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Fig. 5

Optical access windows: NGVs (1), combustion chamber (2), and rotor windows with air purge (3)

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Fig. 6

View through the rotor window showing the turbine blades coated with a sensor coating

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Fig. 7

Coated NGV in position on the engine

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Fig. 8

Phosphorescent signals at different temperatures

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Fig. 9

Calibration procedure experiment

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Fig. 10

Sample orientation during calibration

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Fig. 11

Calibration curve used for the Viper measurements using YSZ:Dy, (1) no temperature sensitivity, (2) low temperature sensitivity, (3) high temperature sensitivity, (4) temperature regime used for the Viper engine

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Fig. 12

NGV measurements; Run A. The new sensor coating system follows the engine operating conditions well and shows very little noise.

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Fig. 13

Combustion chamber; comparison of the Sensor TBC system with a commercial pyrometer for different speed conditions. Tp = pyrometer temperature reading; Ts = sensor coating temperature reading. The graph shows the average temperatures recorded for different operating conditions from 7000 RPM to 13,500 RPM for two different runs. Both instruments show a remarkable repeatability.

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Fig. 14

Rapid load increase; Ts is detected looking through a flame. The data from the inner liner can follow the strong temperature increase and shows a temperature peak at 750 K.

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Fig. 15

Life time decay phosphorescence signal from a turbine blade at a speed of 13,000 RPM using the OPETS probe. The signal from YAG:Eu is a single shot exposure and shows very low noise.




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