58961 - Combustor Wall Surface Temperature and Heat Flux Measurement Using a Fiber-Coupled Long Wave Infrared Hyperspectral Sensor 

Advanced gas turbine engines operate at higher temperatures to increase power, improve fuel consumption, and produce lower emissions into the environments. These new designs require better film-cooling design and improved materials inside the engines. Engine component surface temperature and heat flux measurements are crucial to achieve the optimized engine performance and to prevent engine failures. Therefore, it is pertinent to obtain accurate temperatures and heat fluxes of these combustor walls during operation. Thermocouples are commonly used for engine component surface measurements. However, current commercially available high-temperature thermocouples have difficulty in making reliable measurements in most large gas turbine engines because its high failure rates and high uncertainty at elevated temperature. Additionally, the thermocouples installed are also intrusive and affect the local flow and flame dynamics in the combustor. In the current research work, we discuss the development of a non-intrusive surface temperature sensor based on long-wavelength infrared (LWIR) hyperspectral technology. The LWIR detection enables to minimize optical interferences from hot combustion gases (emission mostly within UV-Mid IR region). Utilization of hyperspectral detection allows to further improve temperature measurement accuracy and precision. The developed sensor with fiber coupling provides the required flexibility to be maneuvered around/through combustor hardware. The LWIR fiber probe is fully protected by the custom-design water-cooled probe housing. This device can sustain temperature of 2400 K at pressure of 50 bar, which enables long-term optical diagnostics inside the practical high-pressure combustion facilities where encounter extreme thermal acoustic perturbation and intense heat fluxes. The housing featured a diamond window to selectively measure spectra in the LWIR region to get accurate surface temperature exclusively of the combustor wall. The probe was installed into a RQL style combustor to get surface temperature of the both hot and cold side of the combustor wall. The heat flux of the combustor wall was successfully derived from the surface temperature measurements. To our knowledge, this is the first time obtaining accurate surface temperature from the hot side of the combustor wall and deriving the desired quantitative heat flux information. The developed LWIR sensor suite shows significant promise in its application to surface temperature and heat flux measurements, and our findings can aid propulsion system engineers and researchers in system design and operation optimization.