Temperature Measurement of Glowing Embers with Color Pyrometry

Abstract

The surface temperature of glowing embers are important for determining the burning rate of embers as they fall and their ability to ignite a target fuel when they land. Temperature measurements of glowing embers using Color Pyrometry (CP) are presented. CP allows for temperature measurement of an incandescing gray or black body based on the intensity’s spectral distribution rather than absolute intensity, and it can be accomplished with a DSLR camera. The CP measurements are compared with measurements using an infrared (IR) camera; it was observed that the CP measurements were more accurate than IR measurements because IR measurements need knowledge of the surface’s emissivity. We show that the emissivity is very important because the transient accumulation and shedding of ash on the surface of the glowing ember changes the emissivity dynamically, consequentially changing the measured temperature. The insensitivity of CP to emissivity allows this method to provide a more robust temperature measurement. Experiments using CP were performed with embers of different sizes in different airflows. The results show that the temperature of the glowing embers increases with increasing air flow. The measured mean glowing temperatures ranged from \(750^\circ \mathrm{C}\) at 1 m/s to \(950^\circ \mathrm{C}\) at 4 m/s. A glowing combustion model explains the dependence of the temperature on the air speed.