3-D Reconstruction Of Flames Based On Single Camera Imaging And Cone-beam Tomographic Techniques

In the combustion process of electric power generation,it's important to measure quantitatively the characteristics of flames in the boiler.As a non-intrusive method,the 3-D(three-dimensional)monitoring and characterization of the flames can help the optimization of the combustion process.By means of tomography,the 3-D flame volume can be reconstructed.In this research,the passive optical tomography method is used to perform the flame reconstruction due to its advantages over other techniques,including simplicity,high resolution and low maintenance.In most passive optical tomographic systems,however,there exists the inconsistency between the optical set-up and mathematical model which introduces errors in the reconstruction results.Most conventional reconstruction algorithms are based on the assumption of parallel projections,i.e.,the projection rays of pixels are assumed to be parallel to the optical axis of a particular view.In many practical cases,however,the flame projections are generally formed by stacked fan-beams or cone-beams.The assumption of the parallel-beams will result in a reduced accuracy in the flame reconstruction,particularly for the flame region which is away from the optical axis.This research presents a methodology for the 3-D reconstruction of an axisymmetric flame based on single camera imaging and cone-beam tomographic techniques.An FDK-based analytic tomographic algorithm is developed.Computational simulations are undertaken to evaluate the effectiveness of algorithm proposed for the reconstruction of different geometric templates.Experimental tests are also conducted using a CCD camera to capture images of a lab-scale flame.The 3-D reconstruction of the flame based on the FDK-based cone-beam tomographic method is then performed based on the images obtained.Both the simulation and experimental results demonstrate the feasibility of the proposed cone-beam based tomographic algorithm for the 3-D flame image reconstruction with a high accuracy and fast system response,compared with the parallel structure.