Evaluating Thin-Film Thermocouple Performance on Additively Manufactured Turbine Airfoils

Abstract

As gas turbine engine designs continue to target higher turbine entry temperatures for increased thermal efficiency, gas turbine manufacturers and operators require additional feedback from life-limited engine components. Moreover, additively manufactured (AM) hardware is becoming more prevalent in the engine development cycle to reduce component lead times and associated costs. Although additive manufacturing unlocks unique capabilities for sensor integration, the inherent roughness from additive surfaces poses unique challenges to the direct-write sensor installation processes. The current study addresses these realities by demonstrating sensor operation on additively manufactured vane hardware in a turbine research facility operating at scaled conditions. Thin-film thermocouples were deposited on fully-cooled AM turbine vanes and tested over a range of operating conditions in a one-stage research turbine at Penn State University. The low-profile surface-mounted sensors were compared with traditional small-diameter embedded thermocouples in terms of calibration accuracy and durability. A comparison between traditional masked thermal spray and direct-write installation was also evaluated as part of the sensor integration strategy for the AM vanes. Ultimately, this study shows that thin-film thermocouples on additively manufactured airfoils can operate reliably over an extended test campaign in rig-scaled conditions. Furthermore, the measurement accuracy of thin-film thermocouples demonstrated through this study is equivalent to traditional mineral-insulated thermocouple sensors showing the utility of these technologies for future turbine research and development applications.