An infrared pyrometer for measuring 700-900 Kelvin surface temperatures in a combustion gas background environment

A technique, utilizing infrared radiometry, has been developed for measuring 700-900 Kelvin (K) surface temperatures in a pressurized, high temperature combustion gas environment. Intense background radiation from combustion gases hampers measurements of the radiant power flux from low temperature sources. Because gaseous thermal radiation is restricted to certain discrete wavelength bands, background hot gas radiation can be eliminated by simple filtering devices. An investigation into the infrared spectral characteristics of hydrocarbon-air combustion byproduct gases led to the development of a simple radiation pyrometer using an interference bandpass filter, lead selenide detector and sapphire optics. This pyrometer successfully followed the 700 to 900 K temperature excursions of a cavity radiator infrared source blocked by a methane-air flame. The pyometer's design and test results are presented.