An overview of the measurement errors associated with gas turbine aeroengine pyrometer systems

It is advantageous to operate the thermodynamic cycle of an aeroengine at as high a turbine entry temperature as practical for the current metallurgical limits of the turbine blades, in order to achieve peak cycle efficiency and thus lower specific fuel consumption. However, achieving the highest possible turbine entry temperature requires accurate knowledge of the turbine blade temperatures for control purposes to prolong component life, as frequent excursions beyond the design limits of the blades can severely reduce their service life. The optical pyrometry technique represents the best method for providing these crucial temperature data needed for blade condition based monitoring. However, this method of non-contact temperature measurement is subject to a number of errors inherent to the gas turbine operating environment. In this paper we present the general operating principles and an overview of the measurement errors associated with optical pyrometry, together with a discussion of the techniques to prevent, limit and compensate for such errors resulting from the turbine environment.