An integrated approach to the application of high bandwidth optical pyrometry to turbine blade surface temperature mapping

As gas turbine manufacturers strive for improved efficiency the turbine operating temperatures increase which can only be met by improvements in blade and coating materials together with advances in cooling and coating technologies. The ultimate, and possibly the only, environment capable of testing modem blade systems is in a working engine and it is from this environment that instrumentation a range of instrumentation technologies must acquire valid blade performance data. A critical blade parameter is the surface temperature distribution and this paper reviews the various technologies currently applied to blade surface temperature distribution measurement. Optical Pyrometry is discussed in more detail and the definition of an integrated high bandwidth detection and data collection system developed. The system developed collects turbine and stores radiance measurements at the rate of 1 million per second and this paper explores the benefits that can accrue from this approach in areas such as noise reduction and blade scanning techniques. The output from such a system is a data file representing a 'thermal image' of all the blade surfaces viewed by the pyrometer. The conversion of the 'thermal image' into a temperature image is discussed and the role of complimentary measurement methods in refining the temperature image is reviewed. The integration of measurement techniques limits the ability of suppliers to deliver an 'Off-The-Shelf' measurement capability. In the light of this the limitations of the system outlined in the paper are discussed and the need for collaborative effort between the system supplier and the users technical departments emphasised.