Abstract

Gas turbine engines are requiring an increasing amount of controls and control accuracy for more stringent emissions compliance and advanced operational methods. Turbine Rotor Inlet Temperature (TRIT) is a very important parameter for calculating performance and life of hot gas path components. Traditional methods for measuring TRIT on a gas turbine engine suffer critical limitations in the harsh environment of the turbine inlet. In this paper, an optical emission temperature measurement technique, known as the integrated spectral band ratio (ISBR) method, is described as a solution being implemented at Solar Turbines Inc. to measure TRIT. The ISBR method is non-intrusive and uses correlated integrated spectral band ratios of water emission to determine the temperature, comparable to two-color pyrometry, developed by Dale Tree at Brigham Young University (BYU). The ISBR method claims the ability to measure actual, view-angle averaged, real-time gas temperature. Also, since it uses water emission measurements rather than absorption it only requires a single point of entry and no laser is used. Use of this method to measure temperature offers many benefits, including real-time fast-response measurements, accurate temperatures measured directly from the fluid in the turbine, single-point measurement hardware, non-intravenous probes, no need for probe cooling, and high-temperature and harsh environment suitability. Applications of the ISBR method to measuring TRIT include better data in research, faster response times in controlling the turbine, higher accuracy in controlling the turbine over various operating conditions, and providing an additional source of measurement for uncertainty and troubleshooting purposes.

The ISBR method was previously developed for atmospheric pressure applications in boilers. Initial testing was performed at Solar Turbines Inc. to validate its use with gas turbine engines. Tests at atmospheric pressure were performed with a single injector test rig and a full combustion system test rig. Testing was performed with custom hardware using cooled probes and Silica optical fibers. Software used to analyze the measurements and produce temperature predictions was written and modified for testing based on previous development efforts at BYU. The intention of these tests was to provide initial replication validation of the ISBM method and set the expectations for future development efforts. Replication was deemed satisfactory, and results show promising application to gas turbine temperature monitoring capabilities at the turbine inlet. Future development applications focus on improved accuracy for heat balance measurements in test cells, transient measurements for off-design CFD validation, flame detection for high hydrogen fuel usage, and improved emission controls for fielded engines.