Theories And Experiments On Four-Demensional Deflection Tomography For Premixed Combustion

The visualization and measurement of complex flow are of major importance in aerodynamics. The measurement and accurate description of flow field structure, parameter distribution and combustion process have hindered the development of new combustion technologies and combustors. Deflection tomography is a powerful tool for measuring complex flow fields because of its many advantages, which include low sensitivity, noncontact measurement, and large dynamic range.The distribution of premixed combustion parameters and the flame structure were investigated in this work using deflection tomography technology. A deflection tomographic apparatus was presented to obtain chronological arrays of multidirectional deflectograms. Deflection projections in different view angles can be captured synchronously in same optical path and same time condition by high speed camera system. Hybrid regularization is obtained by combining total variation method and Tikhonov regularization. Beam deflection angles obtained from moire deflectograms are integrated to optical path length differences, and a modified regularization method is applied to the linear projection equations. The conjugate gradient method is used to compute the regularized solution for the least-square equations. The hybrid regularization method and Tikhonov regularization was employed to simulate asymmetrical distribution. In numerical simulation, the average errors and the maximum value errors computed by hybrid regularization lower than the result that computed by the Tikhonov regularization. The hybrid regularization method showed the superiority in smoothness and peak reconstruction. In experiment, projection array sampling system is employed for combustion flow field sampling in 6 view angles. Hybrid regularization method is used to reconstruct the temperature distributions of combustion flow field in different cross section. The Sobel operator was applied to the threshold segmentation of the two-dimensional temperature distribution. Reconstruct temperature distribution based on four different time’s 20 cross sections and 150 moire fringes. Interior temperature distributions in 5 cross sections of the premixed combustion were arranged to obtain the volume data. Visualization technology with the matching cube and ray casting algorithms was applied in flame structures and temperature distributions four-dimensional visualization.