Temperature Measurement of Model Gas Turbine Combustor Using a Multi-Wavelength Pyrometry in Visible and Near Infrared Spectrum

Abstract Continuous control and monitoring of the gas turbine combustor wall is essential for preventing combustor liner from overheating which may significantly damage structural integrity and reduce overall lifespan. In the past half century combustor outlet temperature has risen from 1100 to 1850 K. The continuous increase of severity of operating conditions inside combustor demands for a temperature determination method whose operation and accuracy are not affected by ever rising temperature. Conventional methods such as thermocouples and thermographic phosphor are not only intrusive, but their operation is also either restricted by an upper temperature limit (thermocouple) or measurement accuracy significantly decreases with increasing temperature beyond a certain threshold (thermographic phosphor). In this paper a multi-wavelength pyrometry system is developed which provides a fast, minimally intrusive temperature determination of the combustor wall. This method does not require any prior knowledge of exact emissivity but of the functional relationship between emissivity and wavelength over the spectral region of interest. One of major problems of wall temperature measurement using a pyrometry in combustor is that the emission from the combustor wall is interfered by the emissions from molecular radicals existing in the flame such as CH* (∼431nm), OH* (∼308nm), CO2* (400–600 nm) in the visible range and major species such as H2O (1.4,1.9,2.7,6.3 um) and CO2 (2.7,4.3,15 um) in the infrared region. In this report, a combustor which is made of stainless steel and runs on natural gas is used and the spectrum of flame emission is measured to identify a proper wavelength range (650–800 nm) over which there exists minimal or no interference from flame emission with thermal radiation. Thermal radiation is measured within the mentioned spectral range with spectrometer and camera assembly from the target spot on the combustor wall with temperature ranging from 1000 to 1200K. Measured temperatures are found to be in good agreement with temperatures measured with thermocouple with absolute error being within 5% or less.