(A) Study on the generation & degeneration of 3-dimensional data from / into 2-dimensional images - combustion diagnostic applications

Abstract

The objective of this thesis is to study the methods of extracting more useful information from limited data generated by combustion studies. Specifically, signals of optical emission or extinction measurements are integrated over the path. In this case, 2-dimensional experimental results of optical combustion diagnostics may be used to generate 3-dimensional data. On the other hand, 3-dimensional experimental or numerical results are difficult to handle. In this case, visualization using the degeneration concept would be useful to observe overall structures. These are the approaches in this study of generation of 3-dimensional data from 2- dimensional images, and 2-dimensional image generation from 3-dimensional scalar data field information. By modifying the radiative transfer equation, the single wavelength/multiple projection inversion tomographic technique was applied to the combustion fields. Photographic image is the line-of-sight emissions from an axisymmetric diffusion flame. The image data were measured using a CCD array camera and a frame grabber, and then used to reconstruct the original 3-dimensional spatially resolved distributions of emission intensities by using the computed tomographic technique. The reconstructed volumetric emission intensities were then converted into optical temperatures of soot particles by assuming that the system response parameters were constant. The constants were determined from the calibration tests with a blackbody cavity and thermocouple measurements. The reconstructed temperatures of soot particles showed reasonable resemblance to the expected distribution. Characteristics of the optical system, such as F-number and pixel distance (magnification of images), with respect to the accuracy of 3-dimensional reconstructed data were discussed. For fuel-lean premixed flat flame and Bunsen burner flame, CH ($A^2Δ→X^2Π$ transition)radical distributions were measured using a two-axis scanning mirror system and monochromator. ...