Validation of Surface Temperature Measurements on a Combustor Liner Under Full-Load Conditions Using a Novel Thermal History Paint

The ever-increasing requirements on gas turbine efficiency and the simultaneous demand for reduced emissions, necessitate much more accurate calculations of the combustion process and combustor wall temperatures. Thermal history paints (THPs) is an innovative alternative to the established measurement techniques, but so far only a limited number of tests have been conducted under real engine conditions. A typical THP comprises oxide ceramic pigments and a water-based binder. The ceramic is synthesized to be amorphous and when heated it crystallizes, permanently changing the microstructure. The ceramic is doped with lanthanide ions to make it phosphorescent and as the structure of the material changes, so do the phosphorescent properties of the material. By measuring the phosphorescence, the maximum temperature of exposure can be determined, enabling postoperation measurements at ambient conditions. This paper describes a test in which THP was applied to an impingement-cooled front panel from a combustor of an industrial gas turbine. The panel was instrumented with a thermocouple (TC), and thermal paint was applied to the cold side of the impingement plate. The THP was applied to the hot-gas side of this plate for validation against the other measurement techniques and to evaluate its resilience against the reacting hot gas environment. The durability and temperature results of the three different measurement techniques are discussed. It is shown that the THP exhibited greater durability compared to the conventional thermal paint. Furthermore, the new technology provided detailed measurements indicating local temperature variations and global variations over the complete component.