Development of high temperature Thermal History Paints for reliable off-line measurements
File(s)
Author(s)
Castillo-Gutierrez, Daniel
Type
Thesis
Abstract
Temperature measurements are of great importance for the operation and maintenance of combustion engines in automotive, aviation and power generation sectors. The development of efficient engines in these sectors will have a decisive impact in the fight against climate change over the coming decades. Conversion technologies, such as gas turbines, can help to reduce CO2 emissions, while transitioning from fossil fuels to renewable energy sources. In this context, the validation of temperatures in new engine designs is critical, in particular for turbomachinery components exposed to the harsh conditions of the combustion environment. Current techniques show critical limitations measuring temperatures on the surface of complex-shaped components, such as rotating turbine blades. The use of off-line temperature measurement techniques can overcome some of these limitations, delivering the maximum temperature seen on the surface of rotating turbomachinery components in harsh combustion environments.
This investigation focuses on the development of a novel off-line surface temperature technique, Thermal History Paint (THP). This technique consists of a luminescent pigment and a liquid binder, functional to temperatures up to 900 °C on metallic substrates. The behaviour of THP based on potassium silicate binder was studied in this work, revealing the main limitations to high temperature functionality. The obtained results revealed interaction between the pigment and the binder and interaction between the THP layer and the metallic substrates. As improvement points, the pigment and the binder were modified, and several interlayers were evaluated between the THP and stainless-steel substrates. While interlayers did not improve the behaviour of the THP, substituting the binder showed some enhanced behaviour at high temperatures. One binder, Ludox® SM30, showed good attachment to metallic substrates, and good behaviour as a carrier of thermographic phosphors.
The combination of the new binder, Ludox® SM30, and the previous potassium silicate binder was tested in order to obtain a high temperature version of thermal history paint. A new THP formulation containing Ludox® SM30 (47.5 % wt.), potassium silicate (47.5 % wt.) and Y2SiO5: Eu3+ (5 % wt.) showed a temperature upper limit extended to 950 °C, and low interaction between the pigment and the binder. This formulation delivered reliable temperature measurements, with uncertainties of +/- 8 °C, for 95 % confidence levels. These results demonstrate the utility of thermal history paints as a durable technique for monitoring temperature engine components, with an uncertainty in the same range of thermocouple readings.
This investigation focuses on the development of a novel off-line surface temperature technique, Thermal History Paint (THP). This technique consists of a luminescent pigment and a liquid binder, functional to temperatures up to 900 °C on metallic substrates. The behaviour of THP based on potassium silicate binder was studied in this work, revealing the main limitations to high temperature functionality. The obtained results revealed interaction between the pigment and the binder and interaction between the THP layer and the metallic substrates. As improvement points, the pigment and the binder were modified, and several interlayers were evaluated between the THP and stainless-steel substrates. While interlayers did not improve the behaviour of the THP, substituting the binder showed some enhanced behaviour at high temperatures. One binder, Ludox® SM30, showed good attachment to metallic substrates, and good behaviour as a carrier of thermographic phosphors.
The combination of the new binder, Ludox® SM30, and the previous potassium silicate binder was tested in order to obtain a high temperature version of thermal history paint. A new THP formulation containing Ludox® SM30 (47.5 % wt.), potassium silicate (47.5 % wt.) and Y2SiO5: Eu3+ (5 % wt.) showed a temperature upper limit extended to 950 °C, and low interaction between the pigment and the binder. This formulation delivered reliable temperature measurements, with uncertainties of +/- 8 °C, for 95 % confidence levels. These results demonstrate the utility of thermal history paints as a durable technique for monitoring temperature engine components, with an uncertainty in the same range of thermocouple readings.
Version
Open Access
Date Issued
2021-12
Date Awarded
2022-06
Copyright Statement
Creative Commons Attribution NonCommercial NoDerivatives Licence
Advisor
Skinner, Stephen
Aguadero, Ainara
Sponsor
Sensor Coating Systems (Firm)
Publisher Department
Materials
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)