Two applications of thermography for testing and development of turbomachinery components are described:
(1) Fabrication defects in the cooling system of internally cooled turbine blades are detected by transient heating of the blade and measuring its surface temperature distribution by an infrared imaging system. Defects like blocking, narrowing, widening and mispositioning of cooling channels can clearly be identified by the disturbance of the transient surface temperature distribution of the blade.
(2) To improve the cooling configuration of turbine blades the cooling effectiveness over the total blade surface must be determined under test conditions similar to those in the turbomachine. The infrared measurement of blade surface temperature distributions in an hot air cascade and the method, to correct the infrared intensities for radiation reflected at the measuring surface, are illustrated in an example.
"Test Of Jet Engine Turbine Blades By Thermography", Proc. SPIE 0520, Thermosense VII: Thermal Infrared Sensing for Diagnostics and Control, (20 March 1985); doi: 10.1117/12.946131; https://doi.org/10.1117/12.946131