Experimental Research on Surface Temperature Measurement of Steam Turbine Rotors Based on IR Thermometry

The surface temperature measurement of steam turbine rotors is of great importance to thermal stress monitoring and security evaluation. Traditionally, the temperature is calculated indirectly by empirical formulas with the vapors’ temperature measured by thermocouples. However, there is huge deviation among the results from different empirical formulas, and which may lead to inaccuracy that cannot be ignored to some extends. In this paper, the feasibility of surface temperature measurement of steam turbine rotors based on infrared radiation (IR) thermometry was discussed and verified experimentally considering the characteristics of the rotors (e.g. high speed rotation, vibration, high-temperature and high-pressure steam, and temperature variation). In the first experiment, the oxidation of alloy samples named refined 12%Cr steel was conducted in a high-pressure steam vessel, and the spectral emissivity of the samples were measured with a monochromatic pyrometer in 1.6μ m. The results shows that the compact oxidation film on the surface of samples had high emissivity, which fitted with a polynomial of third order to the temperature measurements. Then, in the second experiment, the monochromatic pyrometer was used to detect the surface temperature of metal, which was surrounded with high parameters steam(supercritical parameter: up to 25.7MPa and 395°C). The results indicate that the technology of infrared temperature measurement could be applied to the steam turbine rotors, and the deviation can be controlled under 5°C with appropriate infrared emissivity(e.g. assuming e = 0.85). At last, the uncertainty of the temperature measurements was discussed for further work.