Optical Measurements: Techniques and Applications

ISBN-13: 9783540666905 / Angielski / Twarda / 2001 / 405 str.

F. Mayinger; Oliver Feldmann; Franz Mayinger

Opis

Increasing possibilities of computer-aided data processing have caused a new revival of optical techniques in many areas of mechanical and chemical engi neering. Optical methods have a long tradition in heat and mass transfer and in fluid dynamics. Global experimental information is not sufficient for de veloping constitution equations to describe complicated phenomena in fluid dynamics or in transfer processes by a computer program. Furthermore, a detailed insight with high local and temporal resolution into the thermo and fluiddynamic situations is necessary. Sets of equations for computer program in thermo dynamics and fluid dynamics usually consist of two types of formulations: a first one derived from the conservation laws for mass, energy and momentum, and a second one mathematically modelling transport processes like laminar or turbulent diffusion. For reliably predicting the heat transfer, for example, the velocity and temperature field in the boundary layer must be known, or a physically realistic and widely valid correlation describing the turbulence must be avail able. For a better understanding of combustion processes it is necessary to know the local concentration and temperature just ahead of the flame and in the ignition zone."

Spis treści

1 Introduction.- 2 The Schlieren Technique.- 2.1 Introduction.- 2.2 Basic Principle.- 2.3 Optical and Thermodynamic Interrelations.- 2.3.1 Refraction Index and Temperature Field.- 2.3.2 The Deflection of Light in an Inhomogeneous Medium.- 2.4 Application of the Schlieren Technique.- 2.4.1 Application to Transient Combustion Research.- The Schlieren Cinematography.- The Color Schlieren Technique.- 2.4.2 Application to Fuel-Injection Systems.- 3 Fundamentals of Holography and Interferometry.- 3.1 Abstract.- 3.2 Introduction.- 3.3 Principle of Holography.- 3.4 Simple Holographic Arrangement.- 3.5 Holographic Interferometry.- 3.5.1 Double Exposure Technique.- 3.5.2 Real-Time Method.- 3.5.3 Evaluation of the Interferograms.- 3.5.4 Finite Fringe Method.- 3.6 An Interference Method for Simultaneous Heat and Mass Transfer.- 3.7 Comparison with Classical Methods.- 4 Holographic Interferometry.- 4.1 Introduction.- 4.2 Components of a Holographic Interferometer.- 4.2.1 Light Source.- 4.2.2 Optical Table.- 4.2.3 Shutter.- 4.2.4 Beam Splitter.- 4.2.5 Attenuation Filter.- 4.2.6 Beam Expander.- 4.2.7 Mirrors, Lenses.- 4.2.8 Recording Materials.- 4.2.9 Piezo Mirror.- 4.2.10 Test Facility.- 4.3 Evaluation of Interferograms.- 4.3.1 Theoretical Principles.- 4.3.2 Conclusions.- 4.3.3 Calculation of Temperature and Concentration Distributions.- 4.3.4 Determination of the Local Heat Transfer Coefficient.- 4.4 Examples.- 4.4.1 Determination of the Temperature Distribution in a Compact Plate Heat Exchanger with Plain Fins.- Description of the Test Section.- Description of the Interferograms.- 5 Short Time Holography.- 5.1 Introduction.- 5.1.1 Historical development of holography.- 5.1.2 The holographic image.- 5.1.3 Holography as an optical measurement method.- 5.2 Elements of holography.- 5.2.1 Recording materials.- 5.2.2 The pulsed laser.- 5.2.3 Optical set-up.- 5.2.4 Adjusting the holographic camera.- 5.2.5 Recording, development and reconstruction of holograms.- Amplitude hologram.- Phase hologram.- 5.3 Application example: Dispersion characteristics in stirred bubble columns.- 5.3.1 Statement of the problem.- 5.3.2 Recording the holograms.- 5.3.3 Reconstruction and evaluation of the holograms.- 5.3.4 Stereo matching of the two holograms.- 5.3.5 Results.- 6 Evaluation of holograms by digital image processing.- 6.1 Introduction.- 6.1.1 Digitization of a picture.- 6.1.2 Gray value pictures.- 6.1.3 Operations with gray value images.- 6.2 A digital image processing system for the evaluation of holographic reconstructions.- 6.2.1 Evaluation of holographic images.- Scanning of in-line holograms.- Scanning of off-axis holograms.- 6.2.2 set-up of a digital image processing system.- 6.3 Image processing.- 6.3.1 Evaluation of single pulsed holograms.- 6.3.2 Evaluation of double pulsed holograms.- 6.3.3 Stereo matching algorithm.- 6.3.4 Accuracy.- 6.4 Evaluation of interferograms.- 7 Light Scattering.- 7.1 Introduction.- 7.2 Scattering Processes.- 7.2.1 Interaction of Light and Matter.- 7.2.2 Elastic Scattering.- 7.2.3 Inelastic Scattering.- 7.3 Light Scattering Techniques in Heat Transfer.- 7.3.1 Mie-Scattering.- 7.3.2 Rayleigh-Scattering.- 7.3.3 Raman-Scattering.- 7.3.4 Laser Induced Fluorescence (LIF).- 7.3.5 Absorption.- 7.4 Concluding Remarks.- 8 Laser—Doppler Velocimetry.- 8.1 Introduction.- 8.2 Principles of LDV.- 8.3 Optics.- 8.4 Signal Processing.- 8.5 Seeding Particles.- 8.6 Determination of Characteristic Turbulence-Quantities.- 8.6.1 Fundamentals of Turbulent Flows.- 8.6.2 Measurement of Turbulence-Quantities.- 9 Phase Doppler Anemometry (PDA).- 9.1 Introduction.- 9.2 General considerations for the application of PDA.- 9.3 Principles of PDA.- 9.3.1 Light-scattering by particles.- 9.3.2 Optical parameters of a Phase Doppler Measurement System.- 9.3.3 Phase-diameter relationship.- 9.4 Measurement accuracy.- 9.5 Applications of PDA.- 10 Dynamic Light Scattering.- 10.1 Introduction.- 10.2 Overview.- 10.3 Light Scattering Theory.- 10.3.1 Scattering Geometry and Assumptions.- 10.3.2 Temporal and Spatial Behavior of Scattered Light.- 10.3.3 Correlation Functions.- 10.3.4 Hydrodynamic Fluctuation Theory.- 10.4 Experimental Methods.- 10.4.1 Homodyne Method.- 10.4.2 Heterodyne Method.- 10.5 Measurement of Thermal Diffusivity.- 11 Raman Scattering.- 11.1 Introduction.- 11.2 Theoretical Basics of Raman Spectroscopy.- 11.2.1 Concentration Measurements.- 11.2.2 Temperature Measurement.- General Considerations.- Thermometry by Rotational Raman Spectroscopy.- Thermometry by Vibrational Raman Spectroscopy.- 11.3 Experimental set-up.- 11.3.1 Laser.- 11.3.2 Focussing and Collection Lenses.- 11.3.3 Spectral Frequency Selection.- 11.3.4 Photon Converters.- 11.3.5 Data Acquisition and Control.- 11.4 Selected Applications.- 11.5 Concluding Remarks.- 12 Laser induced Fluorescence.- 12.1 Introduction.- 12.2 Basic Principles of Laser Induced Fluorescence.- 12.2.1 General Considerations.- 12.2.2 Concentration Measurement.- 12.2.3 Temperature Measurement.- 12.2.4 Tracer LIF.- 12.3 Experimental Setup and Procedures.- 12.3.1 Experimental Setup.- 12.3.2 Experimental and Evaluation Procedures.- 12.4 Selected Applications.- 12.5 Concluding Remarks.- 13 Absorption.- 13.1 Introduction.- 13.2 Line spectra.- 13.2.1 Position.- 13.2.2 Shape and width.- A. Natural line broadening.- B. Doppler broadening.- C. Collisional broadening.- D. Voigt function-Mixed line shapes.- 13.2.3 Line strength.- 13.3 Experimental techniques.- 13.3.1 Overview.- Techniques used in absorption spectroscopy.- 13.3.2 Experimental examples.- A. In situ measurements of ammonia concentration in industrial combustion systems.- B.Fast temperature measurements with tunable diode lasers.- C. Harmonic detection techniques for the measurement of small absorptions.- D. Simultaneous -situ detection of oxygen and water in a full scale waste incinerator with near infrared diode lasers.- E. In situ determination of free radicals in flames.- 14 Pyrometry and Thermography.- 14.1 Introduction.- 14.2 Temperature Radiation.- 14.3 Method of Transmission.- 14.4 Radiation Receiver (Detector).- 14.5 Thermal Cameras — Thermography Image Systems.- 14.6 Pyrometers.- 14.6.1 Classification According to Construction Types.- 14.6.2 Filament and Quotient Pyrometers.- 14.6.3 IR Recording Heads.- 14.7 Error Potential.- 14.7.1 Error Sources During Recording.- 14.7.2 Equipment Error.- 14.7.3 Problems with Thermograph Readings.- 14.8 Appendix.- 14.8.1 Important Constants.- 14.8.2 Further Information and Tables.- 15 Tomography.- 15.1 Introduction.- 15.2 Integral Measurement Methods.- 15.2.1 Absorption Methods.- 15.2.2 Interferometric Methods.- 15.3 Mathematical Reconstruction Methods.- 15.3.1 Algebraic Reconstruction Methods.- Matrix Methods.- Iterative Series Expansion.- 15.3.2 Explicit Reconstruction Methods.- Fourier Transform Method.- Analytical Solution of Integral Equations.- 15.3.3 Comparison of Reconstruction Methods.- 15.4 Implementations.- 15.4.1 Measurement of temperature fields in stirred vessels.- 15.4.2 Measurement of micro- and macromixing with the tomo-graphical dualwavelenght tomography.- 15.4.3 Tomographic measurements of flames with the Schlieren effect.- 15.4.4 Chemical species tomography by near infra-red absorption.- 16 Particle Image Velocimetry.- 16.1 Introduction.- 16.2 Hardware for the experimental set-up.- 16.3 Evaluation software.- 16.4 Three-dimensional flow.- 16.5 Applications.- Nomenclature.- References.

Blurb

This book provides an introduction to the most important optical measurement techniques that are applied to engineering problems. It will also serve as a guideline to selecting and applying the appropriate technique to a particular problem. The text of the first edition has been completely revised and new chapters added to describe the latest developments in Phase-Doppler Velocimetry and Particle Image Velocimetry. The editors and authors have made a special effort not only to describe and to explain the fundamentals of measuring techniques, but also to provide guidelines for their application and to demonstrate the capabilities of the various methods. The book comes with a CD-ROM containing high-speed movies visualizing the methods described in the book.