New gas turbine subgroup studies thermographic phosphors

Since the formation of ISA107, Advanced Measurement Techniques for Gas Turbine Engines, in summer 2010, the committee has established three working groups that have begun work on thermographic phosphors, tip timing, and tip clearance. The committee’s goal is to encompass measurement techniques for gas turbine engines developed for and used in aerospace and industrial applications. (See December InSights article, “New committee ignites on gas turbine engines,” www.isa.org/link/DecIN_turbine.) The group working on standardization of thermographic phosphors is interested in standardizing the definitions of coating durability, efficiency, temperature range, temperature sensitivity, and methods for establishing these characteristics to benefit engine manufacturers and sensor vendors.

While the current focus of funded technical development of thermographic phosphors is in the area of validating turbine engine temperature levels in the test cell environment, the technique is a valuable tool in nearly any other application in which high levels of reflected or extraneous radiation prevent the use of pyrometry. Thermographic phosphors also provide the ability to make optic-based measurements of cryogenic temperatures where there may be too little emitted radiation to enable pyrometric measurements.

The fluorescence-based methodologies involved in the development of the standards promise to provide crucial hot-section information not available before, with the potential for great cost savings by preventing expensive engine failures. The initial beneficiaries of this new set of standards would be the manufacturers of turbine engines, as these standards would allow much more accurate and repeatable measurements on their engines during their test cell evaluations, and could potentially provide them with the confidence in the measurement capability to transition the technology to on-wing application.

Various other potential users of the technology would benefit as well. For example, the thermographic phosphor technique has been successfully used to determine the temperature inside an operating piston engine, to measure the temperature of semi-molten steel as it is being formed, to determine the temperatures in uranium enrichment centrifuges, and to determine the cryogenic temperatures of liquid hydrogen and liquid oxygen fuel tanks.

Various sensor vendors would also benefit by having a single standardized set of requirements established, which would allow them to develop their new products and capabilities and be assured of meeting the needs of their customers as well as being accepted as industry standards.

If you are interested in contributing to the work of this subgroup, please contact the chair, Steve Allison at allisonsw@ornl.gov.

—Written by William Stange, chair of ISA107 and test cell instrumentation lead for the U.S. Air Force. E-mail him at william.stange@wpafb.af.mil.