Two-dimensional measurement of gas temperature in boiler furnace using acoustic CT taking into account the refraction effect of sound-wave paths

摘要

Recently acoustic pyrometry CT has been developed to measure temperature distribution of big furnaces. When the sound wave passes through a non-uniform temperature field, it bends by refraction. However, previous researchers in this realm have taken it as straight. The error due to the refraction greatly influences the reconstruction of temperature fields especially when the distribution is steep. The authors have established the algorithm to take account of it employing the least-square method to reconstruct two-dimensional temperature distribution on the basis of an analysis of refracted beams by use of Fermat's theorem and the calculus of variations. From our previous work by computer simulation, it can be said that a more accurate temperature field can be reconstructed by this algorithm and the steeper the temperature is, the bigger the error is. In this paper, four kinds of temperature fields were given in a boiler and the temperature distribution is reconstructed by the algorithm with and without considering the refraction effect. Both reconstructed distributions are compared and the discrepancies which are much bigger than those predicted in previous researchers' articles are discussed concerning the temperature distribution patterns.