Session: Poster Session

Paper Number: 162861

Uncertainty Evaluation of Thermal History Coatings Up to 1600 °C 

OEMs are continually increasing firing temperatures in gas turbines to boost both engine and fuel efficiency. With state-of-the-art firing temperatures now around 1600 °C, such extreme environments push the limits of engine-component durability and lifetime. Thus, it is crucial to understand the temperature distribution across component surfaces to drive progress through rapid component prototype screening and thermal model evaluation.

An emerging off-line temperature measurement technique - Thermal History Coatings (THCs) - utilise atmospheric plasma sprayed (APS) lanthanide doped oxides to record the previous maximum exposure temperature in high temperature combustion environments. When exposed to temperature, the THC structure irreversibly changes, affecting the coatings’ luminescent properties. Through calibration, these changes are then related to a single past temperature of exposure, enabling the evaluation of thermal history at discrete locations across the component surface to generate high resolution thermal mapping data.

Historically, THC calibration have utilised Luminescence Lifetime Decay (LTD) to calibrate temperature; however, recent progress in the field of THC application have applied photoluminescence (PL) emission spectra as a new and alternative technique to calibrate temperature.¹ To improve the efficacy of this technique, the calibration procedure must be optimised for high temperatures with the uncertainty of the technique quantified, the latter being particularly important when comparing THC data with thermal models. For gas turbine operating environments, the uncertainty of a temperature measurement technique is required to be below ±20 °C.

In this work, spectral calibration data for a high temperature THC material is evaluated to identify the emission line parameters with the best temperature resolution and relative sensitivity for thermal history sensing for the temperature range 900-1600 °C. A final down-selection of parameters for sensing is detailed with justification to produce an optimised calibration curve.

In addition, a model which assesses the sources of uncertainty arising from the optimised calibration process is presented; the model considers factors from the calibration PL spectra measurement and heat treatment processes to deliver the estimated uncertainty at 67% and 95% confidence levels. The estimated uncertainty of the technique is calculated to be within the target range of ±20 °C from 900-1600 °C. To validate the uncertainty model, further samples were heat treated with thermocouple monitored temperatures before comparison with the predicted calibration result. Calibrated temperatures for the validation samples all fell inside the uncertainty bounds predicted by the model.

 

1.       Hickey, J. et al. Unique High-Resolution Temperature Mapping of Stage 1 Turbine Vane in a Long-Term Engine Test. (2024) doi:10.1115/GT2024-126737.

Presenting Author: Joseph Counte Sensor Coating Systems Ltd. , University of Nottingham

Presenting Author Biography: Joseph was awarded a Master in Science degree in Chemistry when he graduated from Imperial College London in 2020. From 2021 he has worked as an R&D materials engineer at Sensor Coating Systems Limited, working extensively with the company’s thermal history paints and coatings to deliver thermal mapping data to international clients. He is also a prospective PhD candidate with Sensor Coating Systems and the University of Nottingham studying in the field of coatings and surface engineering for advanced materials.

Authors:

Joseph Counte Sensor Coating Systems Ltd. , University of Nottingham
Silvia Araguas-Rodriguez Sensor Coating Systems Ltd.
Solon Karagiannopoulos Sensor Coating Systems Ltd.
Tanvir Hussain Faculty of Engineering, University of Nottingham
Jörg P. Feist Sensor Coating Systems Ltd.