Pyrometer Design for 2-Color Particle Temperatures Measurements in Large Flames

Design details are given of a 2-Color (intrusive) pyrometer used to measure particle temperatures at "point" locations in "large" coal-water fuel (CWF) flames. The results using this device, and comparative measurements in the same flames obtained by suction pyrometer, have already been reported [ I ] , but not the details of the 2-C pyrometer design; these are provided in this paper. Much of the design is conventional and has been reported previously [2]. What is unique is the design of the tip of the (intrusive) probe used to pick up the radiation signal. This is designed to define a "small" volume in the flame that is the source of the signal from the radiating particles. The basis of the probe design is a 6-nun quartz rod, to pick up the radiation signal, contained in a water-cooled jacket. The view half-angle from the rod into the flame is about 3°, thus defining the bounds of the view volume perpendicular to the view direction. The view depth into the flame is limited by a water-cooled target disc that is held in position by its water-cooling tubes. This distance was generally set at about 5 cm but is adjustable. At this time the device has been used in flames iii combustion chambers of dimensions 2'x2'xIO' . In the context of these dimensions, the viewing volume is considered "point-source". Details of the signal processing are given in the earlier paper [2]; the signal analysis is based on the treatment developed by Macek and Bulik [3]. The paper includes an outline both of the signal processing and analysis procedures, and a summary of earlier pertinent results. The result of principal interest is the difference of up to 400°C between the suction pyrometer and 2-C measurements, assumed to be representative of the ambient gas and reacting particles, respectively. The other aspect of interest discussed is the potential for scale up to boiler flames.