Three-dimensional combustion diagnostics based on computed tomography of chemiluminescence

This paper describes an approach to obtain three-dimensional (3D) imaging measurements in combustion systems based on computed tomography of chemiluminescence (CTC). Past efforts have already recognized the capabilities of CTC for obtaining instantaneous 3D measurements with high temporal resolution. However, past efforts have largely relied on the so-called parallel beam assumption. Such an assumption allows the 3D tomographic problem to be solved as a series of 2D problems, significantly simplifying the mathematics involved in the tomographic inversion. However, as shown by the results obtained in this work, such a parallel-beam approach has several drawbacks. Therefore, this work describes an alternative and more general approach to obtained 3D combustion measurements based on CTC. A ray-tracing technique based on Monte Carlo was developed to analyze the tomographic problem with non-parallel beam (i.e., arbitrary). A hybrid algorithm, which combines traditional Algebraic Reconstruction Technique (ART) with the Simulated Annealing (SA) algorithm, was then developed to solve the inversion problems. The paper reports simulation results to illustrate the advantages of the new approach, and also proof-of-concept experimental demonstrations of the new approach.