Remote temperature sensing on and beneath atmospheric plasma sprayed thermal barrier coatings using thermographic phosphors

Nada, Fahd Jouda Abou; Lantz, Andreas; Larfeldt, Jenny; Markocsan, Nicolaie; Aldén, Marcus; Richter, Mattias

doi:10.1016/j.surfcoat.2016.06.038

Cited by 17 publications

(3 citation statements)

References 17 publications

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“…Downconversion phosphor thermometry, i.e. excitation wavelength shorter than emission wavelength, with phosphor layers embedded on top of the bond coat layer and on the surface of TBCs, has been used [2][3][4][5]. In addition, downconversion measurements on uniformly lanthanide-doped TBC layers have also been performed [6,7].…”

Section: Introductionmentioning

confidence: 99%

“…YSZ TBCs can contain impurities in the form of lanthanide ions, which make the TBC material optically active and can interfere with detecting the desirable phosphor luminescence signal [2]. This is particularly an issue when the phosphor layer is at the bottom of the TBC, as the excitation laser light is stronger at shallow depths into the TBC, and the path length of the stimulated luminescence is shorter if it is emitted at a shallow depth in the coating.…”

Section: Introductionmentioning

confidence: 99%

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Upconversion phosphor thermometry for use in thermal barrier coatings

Feuk

Nilsson²,

Richter³

2023

Meas. Sci. Technol.

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Measuring the temperature below the surface of a thermal barrier coating (TBC) using a thin phosphor layer is challenging primarily due to the absorption and scattering of laser excitation light and phosphor luminescence as they propagate through the coating. One way to increase phosphor luminescence could be to use upconversion phosphor thermometry, which is investigated in the current study. It is attractive because using longer excitation wavelengths reduces the absorption and scattering in TBCs as 8 % wt. Yttria-Stabilize Zirconia (8YSZ) generally has lower scattering and absorption coefficients around 1000 nm than at 532 and 355 nm. Therefore, the viability of upconversion to measure the temperature at the bottom of a TBC was evaluated for the first time and was compared with the more conventional downconversion phosphor thermometry. The current work involved an experimental study of several phosphors with lanthanides doped in the 8YSZ host, which were excited through downconversion by pulsed 355 nm and 532 nm laser light and through upconversion with 965 nm laser light. The YSZ:Er,Yb and YSZ:Ho,Yb phosphors show promise for upconversion phosphor thermometry. The experimentally acquired optical phosphor characteristics were used to simulate laser light and phosphor luminescence propagation in TBCs using Kubelka-Munk theory. This was to evaluate the signal strength with upconversion excitation compared to downconversion excitation. Upconversion excitation resulted greater signal strength from an embedded phosphor layer than 532 nm excitation and much higher than 355 nm excitation. Upconversion lifetime phosphor thermometry also resulted in improved phosphor lifetime temperature sensitivity. Coupled with reduced interference from background luminescence from impurities in TBCs with upconversion, it is a promising method for temperature measurements with the thermographic phosphor embedded in or underneath a TBC.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Upconversion phosphor thermometry for use in thermal barrier coatings

Feuk

Nilsson²,

Richter³

2023

Meas. Sci. Technol.

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“…Thermographic phosphor temperature sensors have been applied to TBCs in turbine engines since the early nineties [11]. The method can involve either applying the phosphor to the surface of the TBC [3,6] or embedding it as a thin layer within the coating [4,5,[12][13][14]. The excitation light source is typically a laser or light emitting diode.…”

Section: Introductionmentioning

confidence: 99%

Measurements of turbine blade temperature in an operating aero engine using thermographic phosphors

Jenkins

Hess

Allison³

et al. 2020

Meas. Sci. Technol.

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A diagnostic method is introduced for non-contact temperature measurements on the surface of a rotating turbine blade in an operating engine using laser-induced excitation of thermographic phosphor coatings on the blades. Temperature measurements of between 513 °C and 767 °C are demonstrated on a pair of moving turbine blades with a fiber optic probe mounted in the engine at rotational speeds of between 28 000 and 32 750 RPM. The method involves measuring the decay times of laser-induced luminescence from two thermographic phosphors applied to thermal barrier coatings on the turbine blades, one with a short, temperature-sensitive, decay time and the other with a longer, less temperature-sensitive decay time. The phosphors are excited by laser pulses at a wavelength of 355 nm and luminescence is collected at 456 nm from one phosphor and at 485 nm from the other. The effects of motion on the temperature determination are removed by using a ratio of luminescence intensities of the two phosphors. Potential interferences from chemiluminescence, particles, hot surfaces, and reflections within the engine are avoided by limiting the detection to a narrow spectral window around the luminescence wavelengths. The data exhibit high signal-to-noise ratios and the measured temperatures are within the expected range for this engine.

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Temperature Monitoring of Through-Thickness Temperature Gradients in Thermal Barrier Coatings Using Ultrasonic Guided Waves

Yule,

Harris,

Hill

et al. 2024

J Nondestruct Eval

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Ultrasonic guided waves offer a promising method of monitoring the online temperature of plate-like structures in extreme environments, such as aero-engine nozzle guide vanes (NGVs), and can provide the resolution, response rate, and robust operation that is required in aerospace. Previous investigations have shown the potential of such a system but the effect of the complex physical environment on wave propagation is yet to be considered. This article uses a numerical approach to investigate how thermal barrier coatings (TBCs) applied to the surface of many components designed for extreme thermal conditions will affect ultrasonic guided wave propagation, and how a system can be employed to monitor through-thickness temperature changes. The top coat/bond coat boundary in NGVs has been shown to be a temperature critical point that is difficult to monitor with traditional temperature sensors, which highlights the potential of ultrasonic guided waves. Differences in application method and layer thickness are considered, and analysis of through-thickness displacement profiles and dispersion curves are used to predict signal response and determine the most suitable mode of operation. Heat transfer simulations (COMSOL) have been used to predict temperature gradients within a TBC, and dispersion curves have been produced from the temperature dependant material properties. Time dependant simulations of wave propagation are in good agreement with dispersion curve predictions of wave velocity for the two lowest order modes in three thicknesses of TBC top coat (100, 250, and 500 $$\upmu \hbox {m}$$ μ m ). When wave velocity measurements from the simulations are compared to dispersion curves generated at isotropic temperatures, the corresponding temperature represents the average temperature of a gradient system well. Such a measurement system could, in principle, be used in conjunction with surface temperature measurement systems to monitor through-thickness temperature changes.

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Remote temperature sensing on and beneath atmospheric plasma sprayed thermal barrier coatings using thermographic phosphors

Cited by 17 publications

References 17 publications

Upconversion phosphor thermometry for use in thermal barrier coatings

Upconversion phosphor thermometry for use in thermal barrier coatings

Measurements of turbine blade temperature in an operating aero engine using thermographic phosphors

Temperature Monitoring of Through-Thickness Temperature Gradients in Thermal Barrier Coatings Using Ultrasonic Guided Waves

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