Validation of a Thermal History Paint on a Turbine Blade Hot Gas Test Rig Facility

The drive to higher efficient engine and lower emissions is achieved by increasing firing temperatures, using more sophisticated cooling designs and choosing advanced high temperature materials. However, in order to validate the thermal load on the critical components, novel sophisticated temperature measurements are required. According to the Propulsion Instrumentation Working Group (PIWG), over 80% of an aerofoil needs to be measured for test monitoring and to verify durability[1]. Consequently, design engineers require a high-resolution thermal mapping technique.

This poster presents a validation test of a new thermal mapping technology in realistic combustion conditions. The so called Thermal History Technology has two embodiments: Thermal History Paint[2] and Thermal History Coating[3,4]. Both embodiments contain luminescent materials, which are applied onto the surface of a component. When tested in an operating engine, the maximum temperature of exposure is recorded in the paint or coating. After operation, the temperature information can be read-out by an automated laser scanning system and a post-operation calibration. The automated measuring of points across the component allows the data to be printed directly onto a representative CAD drawing.

One of the major benefits of this technique is the grater durability in comparison to other measurement methods e.g. thermo-chromic paints. This can be exploited by operating the paint or coating for longer durations. The effort involved in the assembly, disassembly and testing of the engine can be therefore distributed over different test campaigns, resulting in large cost savings. Also significant is the ability to provide temperature profiles for individual components hence testing different designs during the same engine test.

This poster shows the application of a Thermal History Paint in its typical operational range between 150 and 900°C. The test object was an internally cooled turbine vane instrumented with thirty thermocouples providing time resolved temperature data for test duration of 45 minutes. The thermocouple data was used to conduct a post calibration procedure for the THP. The vane, more than 80mm high, was scanned using two independent scanning systems; a gantry system and an ABB robotic arm both equipped with a laser detection system. 900 individual temperature data points were generated across the entire vane and mapped onto a CAD drawing. The data was validated against the thermocouple readings and FEM predictions[5]. All three data sets were in very good alignment with each other, showing average variations of +/- 4°C.

This test shows that the new thermal history technology can be used as an advanced temperature mapping tool for engine designers.

[1] Propulsion Instrumentation Working Group (PIWG), "Sensor Specifications, Surface temperature mapping”’, 2018. [Online]. Available: http://www.piwg.org/sensor/sensor_stmapping.html. Accessed 30^th January 2020.

[2] C. Pilgrim, D. Castillo, S. Araguas-Rodriguez, S. Karagiannopoulos, J. Fesit, A. Redwood, Y. Zhang, C. Copeland, J. Scobie, C. Sangan, ‘Thermal Profiling of Cooled Radial Turbine Wheel’, GT2020-14932 in ASME Turbo Expo 2020, London, England, UK, 2020.

[3] S. Araguas Rodriguez, M. Ferran-Marques, C. C. Pilgrim, S. Kamnis, J. P. Feist, and J. R. Nicholls, ‘Thermal History Coatings - Part I: Influence of Atmospheric Plasma Spray Parameters on Performance’, in GT2020-16004, London, England, UK, 2020.

[4] M. Ferran-Marques et al., ‘Thermal History Coatings – Part II: Measurement capability up to 1500⁰C’, in GT2020 - 16209, London, England, UK, 2020.

[5] E. Findeisen, B. Woerz, M. Wieler, P. Jeschke, and M. Rabs, ‘Evaluation of Numerical Methods to Predict Temperature Distributions of an Experimentally Investigated Convection-Cooled Gas-Turbine Blade’, no. 50886, V05BT22A012, 2017, doi: 10.1115/GT2017-64205.