Three-dimensional flame measurements with large field angle

Abstract

Abstract:A system for three-dimensional computed tomography of chemiluminescence was developed to measure flames over a large field angle. Nine gradient-index rods, with a 9 × 1 endoscope and only one camera are used. Its large field of view, simplicity, and low cost make it attractive for inner flow field diagnostics. To study the bokeh effect caused by the imaging system on reconstruction solutions, fluorescent beads were used to determine the blurring function. Experiments using a steady diffusion flame were conducted to validate the system. Three models, namely the clear-imaging, out-of-focus imaging, and deconvolution models, were utilized. Taking the bokeh effect into account, the results suggest that based on run-times the deconvolution model provides the best reconstruction accuracy without increasing computational time.

Two-Dimensional Tomographic Simultaneous Multispecies Visualization—Part II: Reconstruction Accuracy

“…These noisy projections then served as input for the reconstruction algorithms and both the tolerance criterion and the normalized error were saved as a function of the iteration cycles. The graphs in Figure 5 only represent the mean values from all 300 reconstructions, but the ratio of mean values It is worth noting, that ART and MART are currently the most frequently used methods in the literature for the tomographic reconstruction of 2D and 3D flame structures in laminar and turbulent flames on the basis of flame chemiluminescence [6,7,10,12,13,15,16,19,[21][22][23]25,26,29] or the volumetric OH-LIF signal [30][31][32][33], as well as tomographic particle image velocimetry (tomo PIV) [2,[34][35][36][37]. The main reason could be that ART and MART are numerically easy to implement and less demanding in terms of memory consumption, which is particularly advantageous for time-resolved 3D tomography.…”

“…To the best of our knowledge, the work of Anikin et al [3,4] is so far the only study that uses Tikhonov regularization for the tomographic imaging of laminar and turbulent flames. The vast majority of tomographic studies on combustion processes uses either the algebraic reconstruction technique (ART) [6,7,[10][11][12][13][14][15][16][17]19,20,23,28,29,60] or its sibling, the multiplicative algebraic reconstruction technique (MART) [21,22,25,26,[30][31][32]. ART was developed independently by Gordon, Bender and Herman [49] and Hounsfield [50].…”

Two-Dimensional Tomographic Simultaneous Multi-Species Visualization—Part I: Experimental Methodology and Application to Laminar and Turbulent Flames

“…It facilitates the detection of 2D or even 3D distributions of the chemiluminescence emission from laminar and turbulent hydrocarbon flames of any geometry. The development and application of tomographic methods for the reconstruction of 2D [20][21][22] and 3D flame structures in laminar [21,22,24,[28][29][30]33,[39][40][41][42] and turbulent [20,23,[25][26][27][30][31][32][34][35][36][37][43][44][45] flames have gained a lot of interest in the past decade. They are used to image the distribution of chemiluminescent species [20][21][22][23][24][25]28,29,[31][32][33][34][35][37][38][39][40][41][42]…”

“…One possibility is to use a special mirror-based relay optic between the flame and the camera, which maps several 2D projections onto each camera, but it still requires three or more cameras [25][26][27]30,42,44,45]. The other option uses a customized bundle of optical fibers to project the chemiluminescence onto the camera sensor [20,21,28,29,32,34,41]. Anikin et al were the first to work with a fiber bundle and to demonstrate the 2D tomographic imaging of laminar and turbulent flame structures with a single image intensified camera [20,21].…”

Design and modeling of pulsed-laser three-dimensional imaging system inspired by compound and human hybrid eye

“…Therefore, this imaging technology is widely used in various applications, including target recognition 4 , robotics 5 , terrain visualization 6 , medical diagnostics 7 , and vehicle navigation 8 . A pulsed-laser 3D imaging system with a large field of view (FOV), high imaging speed and high imaging resolution is critical and exhibits a huge potential in many applications, such as industry, medical and military areas 7 , 9 , 10 . To the best of our knowledge, the imaging principle divides the pulsed-laser 3D imaging system into two categories: scanning and non-scanning types 11 .…”