Approximate Two-Color Emission Pyrometry

Abstract

Approximate methods for the determination of a temperature field using pure emission pyrometry applied to a two-dimensional nonoptically thin flame without variation along a line of sight are presented. In the absence of an absorption measurement, emission pyrometry depends on theoretical spectral information. Limitations of existing techniques stem from the fact that spectral information is a function of temperature only for the optically thin situation, by and large the situation to which current techniques apply, and temperatures above 1000 K. Through extensive narrow-band calculation using a simulated flame over polymethylmethacrylate, we show that the spectral information contained in the equivalent bandwidth ratio is approximately a constant for the 2.8 μm/1.8 μm band pair and appropriate bandwidths. The constant can be evaluated from emission measurements at a point where the temperature is known or can be estimated using, e.g., the maximum flame temperature of a simulated flame and the peak band intensities. The temperature field evaluated with this approximately constant value of the equivalent bandwidth ratio, Ar, is accurate to within five percent for temperatures down to 450 K. [S0022-1481(00)02601-3]