This proposal was received in response to the Sensors and Sensor Networks Solicitation, NSF 04-522, category Individual Investigator Proposals.
Society today relies on gas turbine engines for both the generation of electricity and aircraft propulsion. To increase the overall energy efficiency as well as minimize maintenance, there is a drive to develop new coatings, sensors and controls. The focus of our research is on high-temperature thermal barrier coatings that provide thermal insulation to the turbine blades and combustion chambers allowing engines to be operated at higher temperatures, and hence higher efficiency, than uncoated engines. Specifically, we are developing an all-optical sensor for in-situ measurement of the temperature, and heat flux, across thermal barrier coatings, crucial heat transfer parameters for both "health monitoring" and design validation as well as reliability and life prediction. As the life of the coating, the metal blades and vanes all depend on their maximum temperature, the temperature of the inner coating surface, which is in direct contact with the metal, is a vital but presently unknowable parameter. Likewise, the actual temperature of the coatings' outer surface, as distinct from the gas temperature at the surface, also affects coating life and durability. With measurements of the temperature difference across the thickness of the coating the heat flux can be determined. The basis of our proposed sensor is the characteristic temperature-dependent luminescence from different rare-earth dopants that we incorporate within the crystal structure of existing thermal barrier coating materials. By placing the dopants at different levels in the coating it becomes a structured sensor whose signals come from the positions within the coating where the dopants are located, for instance at the inner and outer surfaces. Although the focus is on temperature measurement in thermal barrier coatings, the methodology, the protocols for selecting of dopants for high-temperature luminescence and the overall sensor design considerations are expected to be of value for other applications where it is important to measure high temperatures of materials and, in particular within structures of materials where optical pyrometer is not feasible or masked by thermal radiation. An integral part of the program is that the graduate students will perform tests of the sensors at NASA Glenn Research Center using the laser-driven high heat flux test rig there, enabling them to also experience a different working environment and learning from research professionals and collaborators.
The proposal is being funded by the Thermal Transport and Thermal Processing Program of the Chemical and Transport Systems Division and the Sensors in Civil and Mechanical Systems Program in the Civil and Mechanical Systems Division.
