Single wavelength and ratio pyrometry reflection errors in temperature measurement of gas turbine blade

• Reflection errors in single wavelength and ratio pyrometers were investigated.
• Low emissivity, high ambient temperature and high view factors increases pyrometer measured error.
• Both single and ratio pyrometers are susceptible to reflection errors.
• Correction of these errors in temperature measurement is quite necessary.

Radiation thermometers are the instruments most opted for when measuring surface temperatures of high speed rotating parts non-intrusively in many industrial applications. However, reflection of ambient radiation from the measured target goes against the operating principles of most of these thermometers thus introducing errors to the temperature measurements. Reflection errors introduced into single wavelength and ratio pyrometer temperature measurements of a rotating cooled gas turbine blade were investigated in this work through simulation. Errors for the two pyrometers based on varied target surface emissivity, view factor and ambient temperature were calculated. At high ambient temperatures, high view factors and low surface emissivity, errors exceeding 70% and 30% were realized for single wavelength and ratio pyrometers respectively. Thus temperature measured on reflective targets surrounded by surfaces at much higher temperature should be corrected for reflection errors if its reliability is to be guaranteed.