Thin-Filament Pyrometry with a Digital Still Camera

Abstract

A novel thin-filament pyrometer is presented here. It involves a consumer-grade color digital still camera with a charged-couple device sensor with 3008 X 2000 pixels and 12 bits per color plane. A blue Schott filter and custom white balance were used to yield similar red, green and blue intensities along the fibers. SiCO fibers with diameters of 13.9 microns were used and scanning-electron microscopy revealed the fibers to be uniform. Measurements were performed in a methane/air coflowing laminar jet diffusion flame with a luminosity length of 72 mm. Calibration of the pyrometer was accomplished with B-type thermocouple measurements. The camera was found to be well suited to thin-filament pyrometry. The pyrometry measurements yielded gas temperatures in the range of 1350 - 2200 K with an estimated uncertainty of ± 60 K, a relative temperature resolution of ± 0.215 K, a spatial resolution of 42 µm and a temporal resolution of 0.66 ms. Fiber aging had no effect on the results. Soot deposition was less problematic for the pyrometer than for the thermocouple.