Optimisation of luminescent thermal history sensors
File(s)
Author(s)
Araguas Rodriguez, Silvia
Type
Thesis
Abstract
Surface temperature measurements are critical in harsh engineering environments such as gas turbines. This need is amplified by governmental regulations requiring higher engine efficiencies to reduce CO2 emissions, resulting in ever-rising firing temperatures. Temperature data enables the evaluation of novel component designs, the assessment of hot spots and validation of thermal and lifing models.
Current temperature measurement techniques incur disadvantages for continuous surface measurements. Common drawbacks include the need for visual access, delivery of point measurements and their destructive nature. Thermal paints deliver surface maps but only provide subjective data with large data gaps and are comprised of toxic constituents. Novel Thermal History Sensors surmount these disadvantages to provide surface temperature data. These are coatings or paints that are applied on a component surface. Interrogation of the coatings following high-temperature exposure with laser-based instrumentation delivers past maximum-temperature data.
The technique relies on a luminescent material, which gradually changes structure as it is heated, thereby impacting its luminescent properties. The luminescence is measured and related, through calibration, to a unique past temperature of exposure. This project optimised Y2SiO5:Eu for temperature sensing, including its synthesis through the sol-gel route and doping with luminescent ions. An in-depth characterisation of the pigment’s structural evolution with temperature and corresponding luminescence properties was performed. The pigment was found suitable for temperature measurements until 1200°C.
A successful Thermal History Paint was proposed, comprised of Y2SiO5:Eu in a soluble potassium silicate binder, to enable surface coverage of the sensor. An exhaustive characterisation of the interaction between the two constituents used the structural characteristics to explain and optimise the paint’s luminescent behaviour. One final formulation was found to deliver temperature measurements in the range 150°C-900°C, with an estimated accuracy of ±10°C. A successful demonstration of the Thermal History Paint on an industrial component was performed on a combustor liner.
Current temperature measurement techniques incur disadvantages for continuous surface measurements. Common drawbacks include the need for visual access, delivery of point measurements and their destructive nature. Thermal paints deliver surface maps but only provide subjective data with large data gaps and are comprised of toxic constituents. Novel Thermal History Sensors surmount these disadvantages to provide surface temperature data. These are coatings or paints that are applied on a component surface. Interrogation of the coatings following high-temperature exposure with laser-based instrumentation delivers past maximum-temperature data.
The technique relies on a luminescent material, which gradually changes structure as it is heated, thereby impacting its luminescent properties. The luminescence is measured and related, through calibration, to a unique past temperature of exposure. This project optimised Y2SiO5:Eu for temperature sensing, including its synthesis through the sol-gel route and doping with luminescent ions. An in-depth characterisation of the pigment’s structural evolution with temperature and corresponding luminescence properties was performed. The pigment was found suitable for temperature measurements until 1200°C.
A successful Thermal History Paint was proposed, comprised of Y2SiO5:Eu in a soluble potassium silicate binder, to enable surface coverage of the sensor. An exhaustive characterisation of the interaction between the two constituents used the structural characteristics to explain and optimise the paint’s luminescent behaviour. One final formulation was found to deliver temperature measurements in the range 150°C-900°C, with an estimated accuracy of ±10°C. A successful demonstration of the Thermal History Paint on an industrial component was performed on a combustor liner.
Version
Open Access
Date Issued
2018-09-29
Date Awarded
01/03/2019
License URL
Advisor
Skinner, Stephen
Sponsor
Royal Commission for the Exhibition 1851
Publisher Department
Materials
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)