Oxygen quenching of phosphorescence from thermographic phosphors

Thermographic phosphor thermometry is a technique for surface temperature measurement which may be employed in the hot sections of a gas turbine allowing temperature detection up to around 1400degreesC with uncertainties better than for other remote standard techniques such as pyrometry. The phosphors have been regarded as pressure insensitive and indeed have been used to provide reference temperature data for the correction of pressure-sensitive paint data. The authors wish to employ the technique in gas turbine combustors where oxygen partial pressure varies widely due to its consumption in the combustion reaction. An experiment was therefore conducted to confirm the pressure/oxygen insensitivity of two high-temperature phosphors. However, this revealed a response to oxygen partial pressure that implies an uncertainty in temperature measurements within the primary zone of a combustor of typically 1%. There does not appear to have been any previous report of such a response in the literature and this note therefore serves as a caution to those employing the thermographic phosphor thermometry technique where oxygen partial pressure varies significantly.