An acoustic pyrometer system for tomographic thermal imaging in power plant boilers

The paper presents an acoustic pyrometry method for the reconstruction of temperature maps inside power plant boilers. It is based on measuring times-of-flight of acoustic waves along a number of straight paths in a cross-section of the boiler; via an integral relationship, these times depend on the temperature of the gaseous medium along the paths. On this basis, 2D temperature maps can be reconstructed using suitable inversion techniques. The structure of a particular system for the measurement of the times-of-flight is described, and two classes of reconstruction algorithms are presented. The algorithms proposed have been applied to both simulated and experimental data measured in power plants of the Italian National Electricity Board (ENEL). The results obtained appear fairly satisfactory, considering the small data sets that it was possible to acquire in the tested boilers.