Effect of pyrometer type and wavelength selection on temperature measurement errors for turbine blades

Turbine blade temperature measurements are important for monitoring the working state of the blades. However, the reflected radiation from the high temperature surrounding environment leads to significant error in the optical pyrometer measurements. This study calculates and compares temperature error of single wavelength pyrometer, ratio pyrometer and multicolor pyrometer in measuring turbine rotor blade temperature. Emissivity of the blade was measured in the wavelength range of 1.2 μm to 2.5 μm. Temperature distribution of the rotor blade and the guide vane was simulated by CFD software. Additionally, temperature error was calculated based on - discretization of a three-dimensional blade model. The results show that from the leading edge to the trailing edge of the rotor blade pressure side, the variation trend of the three kinds of pyrometer temperature error is the same, first decreasing, then increasing before decreasing again. The maximum relative temperature error was found to be 7.5%, 4.9% and 2.6% when the wavelength of the pyrometer was 1.3 μm, 1.6 μm, 2.2 μm, respectively. The study also shows that wavelength selection has great influence on the ratio pyrometer. It was found that the maximum relative temperature error ranged from 2.6% to 15.7% based on the choice of the various wavelengths. On the other hand, the maximum relative temperature error of the multicolor pyrometer was 3.8%. The analysis presented in this work will be of importance in providing guidelines for choosing the optimum measurement wavelengths for optical pyrometers. Furthermore, the finding will also useful in the calculation and correction of the optical pyrometer error.