Simultaneous Short and Long Wavelength Infrared Pyrometer Measurements in a Heavy-Duty Gas Turbine

Markham, James R.; Latvakoski, Harri; Frank, Stefan; Lüdtke, M.

doi:10.1115/1.1473822

Cited by 13 publications

(11 citation statements)

References 9 publications

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“…The requirement for high opacity is especially important when pyrometer measurements are made when there is a significant thermal gradient across the TBC thickness, in which case, penetrating pyrometer measurements will produce misleading results by sampling the cooler subsurface temperatures. Figures 2–4 show that these criteria are met only at wavelengths near 12.5 μm, in fairly close agreement with the recommendations of Markham et al 15 and Pfefferkorn et al 16 to select a wavelength near 11 μm for optimum pyrometer‐based 8YSZ TBC surface temperature measurements. The unsuitability of 1‐μm‐wavelength pyrometers for 8YSZ TBC temperature measurements is clear from the near‐zero emittance (Fig.…”

Section: Discussionsupporting

confidence: 84%

“…Besides being useful for radiative heat transport calculations, the wavelength dependence of the scattering and absorption coefficients will provide guidance for performing pyrometer‐based temperature measurements on TBC‐coated specimens. Markham et al 15 and Pfefferkorn et al 16 have shown the advantages of pyrometer measurements at long wavelengths (near 11 μm), where TBCs exhibit high, constant emittance and low reflectance in contrast to the variable emittance and significant reflectance that introduce significant uncertainties into pyrometer measurements of TBC‐coated components at wavelengths <8 μm. In addition, TBC‐coated specimens present the additional concern that pyrometer measurements performed at wavelengths where the TBC is partially translucent are not true surface temperature measurements.…”

Section: Introductionmentioning

confidence: 99%

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Determination of Scattering and Absorption Coefficients for Plasma‐Sprayed Yttria‐Stabilized Zirconia Thermal Barrier Coatings

Eldridge

Spuckler

2008

Journal of the American Ceramic Society

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Prediction of radiative transport through translucent thermal barrier coatings (TBCs) can only be performed if the scattering and absorption coefficients and index of refraction of the TBC are known. To date, very limited information on these coefficients, which depend on both the coating composition and the microstructure, has been available for the very commonly utilized plasma-sprayed 8 wt% yttria-stabilized zirconia (8YSZ) TBCs. In this work, the scattering and absorption coefficients of freestanding plasma-sprayed 8YSZ coatings were determined from room-temperature normal-incidence directionalhemispherical reflectance and transmittance spectra over the wavelength range from 0.8 to 7.5 lm. Spectra were collected over a wide range of coating thickness from 60 to almost 900 lm. From the reflectance and transmittance spectra, the scattering and absorption coefficients as a function of wavelength were obtained by fitting the reflectance and transmittance values predicted by a four flux model to the experimentally measured values at all measured 8YSZ thicknesses. While the combined effects of absorption and scattering were shown in general to exhibit a nonexponential dependence of transmittance on specimen thickness, it was shown that for sufficiently high absorption and optical thickness, an exponential dependence becomes a good approximation. In addition, the implications of the wavelength dependence of the plasma-sprayed 8YSZ scattering and absorption coefficients on (1) obtaining accurate surfacetemperature pyrometer measurements and on (2) applying midinfrared reflectance to monitor TBC delamination are discussed.

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Section: Discussionsupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Determination of Scattering and Absorption Coefficients for Plasma‐Sprayed Yttria‐Stabilized Zirconia Thermal Barrier Coatings

Eldridge

Spuckler

2008

Journal of the American Ceramic Society

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“…Long wavelength (∼10 microns) pyrometry has been developed to overcome this problem, where TBC emittance is reliably close to 1, and reflectance is close to 0. Long wavelengths are nonpenetrating [55] and have been shown to work effectively during engine tests [56], although the readings are strongly influenced by background radiation. A number of authors have tested pyrometers on turbine engine test rigs [6,57,58].…”

Section: Pyrometrymentioning

confidence: 99%

Surface temperature condition monitoring methods for aerospace turbomachinery: exploring the use of ultrasonic guided waves

Yule

Zaghari

Harris

et al. 2021

Meas. Sci. Technol.

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Turbine blades and nozzle guide vanes (NGVs) are operated at extreme temperatures in order to maximise thermal efficiency and power output of an engine. In this paper the suitability of existing temperature monitoring systems for turbine blades and nozzle guide vanes are reviewed. Both offline and online methods are presented and their advantages and disadvantages are examined. The use of offline systems is well established but their online equivalents are difficult to implement because of the limited access to components. There is the need for an improved sensor that is capable of measuring temperature in real time with minimum interference to the operating conditions of the engine, allowing operating temperatures to be increased to the limits of the components and maximising efficiency. Acoustic monitoring techniques are already used for a large number of structural health monitoring applications and have the potential to be adapted for use in temperature monitoring for turbine blades and NGVs. High temperatures severely affect the response of ultrasonic transducers. However, waveguides and buffer rods can be used to distance transducers from extreme conditions, while piezoelectric materials such as Yttrium Calcium Oxyborate single crystals and Aluminum Nitride have been developed for use at high temperatures. A new monitoring approach based on ultrasonic guided waves is introduced in this paper. The geometry of turbine blades and NGVs allows Lamb waves to propagate through their structure, and the presence of numerous cooling holes will produce acoustic reflections that can be utilised for monitoring temperature at a number of locations. The dispersive nature of Lamb waves makes their analysis difficult; however, wave velocity in dispersive regions is particularly sensitive to changes in temperature and could be utilised for monitoring purposes. The proposed method has the potential to provide high resolution and accuracy, fast response times, and the ability to place sensors outside of the gas path. Further research is required to develop a monitoring system based on the use of guided waves in extreme environments.

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“…A large number of experiments have shown that the emissivity of the thermal barrier coating part is nearly 0.95, while the uncoated part is around 0.55. [3] On the other hand, the different emissivity will have significant differences on the radiation intensity at the same temperature. When the temperature increases, temperature difference will also increase.…”

Section: Turbine Blade Thermal Barrier Coating Detectionmentioning

confidence: 99%

Infrared Thermal Wave Nondestructive Testing Technology and Its Application

Zhou¹,

Cai²

2016

Proceedings of the 2016 International Conference on Computer Engineering, Information Science &Amp; Application Technology (ICC

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The technical principles and characteristics of the infrared thermal wave nondestructive testing technology have been reviewed in this paper. Compared with five conventional nondestructive testing methods, the advantages of infrared thermal wave nondestructive detection technology are highlighted. In addition, this paper describes the applications of infrared thermal wave nondestructive testing technology in some fields that conventional nondestructive testing techniques are difficult to solve, including composites, honeycomb structures, wind turbine blades, etc. The technical features and wide application advantages of infrared thermal wave nondestructive testing have been presented in detail.

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Simultaneous Short and Long Wavelength Infrared Pyrometer Measurements in a Heavy-Duty Gas Turbine

Cited by 13 publications

References 9 publications

Determination of Scattering and Absorption Coefficients for Plasma‐Sprayed Yttria‐Stabilized Zirconia Thermal Barrier Coatings

Determination of Scattering and Absorption Coefficients for Plasma‐Sprayed Yttria‐Stabilized Zirconia Thermal Barrier Coatings

Surface temperature condition monitoring methods for aerospace turbomachinery: exploring the use of ultrasonic guided waves

Infrared Thermal Wave Nondestructive Testing Technology and Its Application

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