Access to Thesis

Access to Electronic Thesis Author: Qian Wang Thesis title: Advanced Optical and 3D Reconstruction Diagnostics for Combustion and Fluids Research Qualification: PhD This electronic thesis is protected by the Copyright, Designs and Patents Act 1988. No reproduction is permitted without consent of the author. It is also protected by the Creative Commons Licence allowing Attributions-Non-commercial-No derivatives. If this electronic thesis has been edited by the author it will be indicated as such on the title page and in the text. Table of Contents Table of Contents .......................................................................................................1 Declaration ………………………………………………………………………………………..... 5 Copyright ……………………………………………………………………………………………6 Publications …………………………………………………………………………………………7 Acknowledgements.....................................................................................................8 Abstract ……………………………………………………………………………………………... 9 List of Figures...........................................................................................................11 List of Tables ……………………………………………………………………….…………….. 18 Nomenclature............................................................................................................19 Chapter 1 Introduction............................................................................................24 1.1 Motivation...................................................................................................24 1.2 Objectives....................................................................................................26 1.3 Outline of the thesis ....................................................................................27 Chapter 2 Literature Review ..................................................................................30 2.1 Combustion background .............................................................................30 2.1.1 Introduction.................................................................................................30 2.1.2 Premixed flames..........................................................................................31 2.1.3 Non-premixed/diffusion flames ..................................................................33 2.1.4 Laminar, turbulent and transitional flames .................................................34 2.2 Optical experimental methods in fundamental combustion research .........36 2.2.1 Schlieren & shadowgraph ...........................................................................40 2.2.1.1 Conventional schlieren and shadowgraph methods ...............................40 2.2.1.2 Schlieren.................................................................................................40 2.2.1.3 Shadowgraph..........................................................................................45 2.2.1.4 Distinctions between schlieren and shadowgraph..................................47 2.2.1.5 Quantitative schlieren.............................................................................48 2.2.1.6 Background-oriented schlieren (BOS)...................................................48 2.2.1.7 Calibration schlieren ..............................................................................50 2.2.1.8 Colour schlieren .....................................................................................51 2.2.1.9 Interference schlieren.............................................................................52 2.2.1.10 Fringe schlieren..................................................................................53 1 2.2.1.11 Synthetic schlieren .............................................................................54 2.2.2 Stereoscopic imaging technique..................................................................56 2.2.3 Three-dimensional schlieren technique.......................................................61 2.2.3.1 Tomography BOS ..................................................................................61 2.2.3.2 Stereoscopic schlieren technique ...........................................................63 2.2.4 Laser Induced Fluorescence (LIF) ..............................................................67 2.2.5 Particle Image Velocimetry (PIV) ..............................................................69 2.2.6 Holographic Technique...............................................................................71 2.2.7 Tomography................................................................................................75 2.2.8 Visual hull reconstruction ...........................................................................77 2.3 Comparison of the selected optical techniques used in combustion field...80 Chapter 3 Principle and Algorithms of 3D Reconstruction Using Stereo Images………………………………………………………………………………82 3.1 Introduction of 3D reconstruction from stereo images ...............................82 3.2 Geometry and optical characteristics of the stereo adapter.........................84 3.3 Two camera system.....................................................................................89 3.4 Algorithms for camera calibration and reconstruction................................90 3.4.1 Projective camera model.............................................................................90 3.4.2 Homography between the model plane and the image ...............................92 3.4.3 Closed-form solution for intrinsic parameters ............................................93 3.4.4 Extrinsic parameters estimation..................................................................95 3.4.5 Depth information reconstruction ...............................................................96 3.5 Camera calibration process .........................................................................97 3.6 Correspondence problem ..........................................................................101 3.5.1 Epipolar constraint ....................................................................................101 3.5.2 Rectification ..............................................................................................102 3.7 Curve reconstruction .................................................................................104 3.8 Surface reconstruction...............................................................................105 3.9 Summary ...................................................................................................107 Chapter 4 Stereoscopic Schlieren/Shadowgraph Imaging System....................108 4.1 Introduction...............................................................................................108 4.2 Experimental setup....................................................................................109 4.3 Synchronisation of the two high speed cameras .......................................110 4.4 Camera calibration ....................................................................................112 2 4.5 Conclusion ................................................................................................117 Chapter 5 Applications of High Speed Stereoscopic Shadowgraph Technique…………………………………………………………………………119 5.1 Introduction...............................................................................................119 5.2 Point reconstruction in static object ..........................................................120 5.2.1 Model introduction....................................................................................120 5.2.2 Selected points reconstruction...................................................................121 5.2.3 Error analysis ............................................................................................123 5.3 Bubble bursting investigation based on point reconstruction ...................124 5.3.1 Bubble bursting process ............................................................................124 5.3.2 Correspondence points..............................................................................126 5.3.3 Bubble bursting rim reconstruction...........................................................127 5.3.4 Specific point tracing ................................................................................129 5.4 Curve reconstruction .................................................................................132 5.4.1 Curve extraction........................................................................................133 5.4.2 Curve picking up from the binary images.................................................135 5.4.3 Curve matching and reconstruction ..........................................................136 5.5 Summary ...................................................................................................137 Chapter 6 Spark Characteristics Investigation of a Gas Turbine Igniter ........140 6.1 Introduction...............................................................................................140 6.2 Experimental setup....................................................................................142 6.3 Spark characteristics investigation............................................................144 6.3.1 Spark initiation performance.....................................................................144 6.3.2 Shockwave and hot gas propagation.........................................................145 6.4 Stereo application on spark performance

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