Research On Acoustic Reconstruction Of Temperature Field

Combustion temperature testing technique is one of the important foundation in combustion theory and technique developing. The temperature field of flame in the hearth has epochmaking meaning as for controlling the boiler and diagnosing combustion. As a new-style temperature measuring method, the acoustic method is much faster and with a high precision as well as a broader measuring range. It can satisfy the requirements of measuring accurately and controlling online on the temperature field in industrial productions and scientific investigations. It has important guidance meaning for optimizing combustion, reducing pollution, equipment moving safely and designing the hearth.The principle and the development status of temperature field measurement by acoustic tomography are introduced in this thesis. By using acoustic sensors, the reconstruction and emulation of temperature fields in a coal fired boiler was studied. Two planes along the boiler axial is selected and the 3D temperature fields enclosed by the two planes was reconstructed. Eight acoustic sensors were assumed to be amounted on each plane and the sound emitted by any one of the eight could be received by the others. Based on the measurement of time of flight of acoustic wave traveling between acoustic sensors and by using least square root, the 2D temperature fields were obtained first, and then the 3D temperature fields about the reconstruction of the Single-peak symmetry temperature field, the Single-peak asymmetry temperature field and the Double-peak temperature field were reconstructed by using linear cubic interpolation according to the 2D temperature fields obtained. Aimed at the typical symmetrical temperature distribution in furnace, the algorithm by used a single path temperature function firstly, then plotted the grid and interpolated is proposed. But this method has limited in some determinate which has better reconstruction effect for Single-peak symmetry temperature field. The effect of curvature of the traveling paths of acoustic wave caused by Fermat Effect on the measurement time of flight result in reconstruction of temperature fields precision were also studied. Toward the number of the sensors, the position of the sensors, the distribution of support domain and other correlation factor has been researched. Considering this factor can improve the precision of the reconstruction temperature field by analyzing the errors. This is accordant with the theory result.