Optical Measurements: Techniques and Applications

461 Pages·1994·12.985 MB·English

by  J. Klas, G. Strube (auth.), Prof. Dr. Franz Mayinger (eds.)

Franz Mayinger (Editor)
Optical Measurements
Techniques and Applications
With 264 Figures
Springer-Verlag
Berlin Heidelberg GmbH
Prof. Dr. Franz Mayinger
Lehrstuhl A fiir Thermodynamik
Technische Universitat Miinchen
ArcisstraBe 21
D-80290 Miinchen
FRG
ISBN 978-3-662-02969-5
Library of Congress Cataloging-in-Publication Data
Optical measurements: techniques and applications I Franz Mayinger, editor.
ISBN 978-3-662-02969-5 ISBN 978-3-662-02967-1 (eBook)
DOI 10.1007/978-3-662-02967-1
I. Optical measurements. 2. Optical measurements--Industrial applications. 3. Interferometry.
I. Mayinger, F.
QC 367-0585 1994
530.8--dc20 94-20068
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Verlag Berlin Heidelberg GmbH. Violations are liable for prosecution act under German Copyright Law.
© SpringerVerlag Berlin Heidelberg 1994
Originally published by Springer-Verlag Berlin Heidelberg New York in 1994
Softcover reprint of the hardcover 1st edition 1994
The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the
absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore
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Contributing Authors
PROFESSOR Institut fiir angewandte Laserphysik,
DR. P. ANDRESEN Universitiit Bielefeld,
Universitiitsstr.25, 33615 Bielefeld, Germany
DR. R. BEAUVAIS Lehrstuhl A fiir Thermodynamik,
Technische Universitiit Miinchen,
Arcisstr.21, 80290 Miinchen, Germany
*
DR. A. CHAVEZ Instituto de Investigaciones Electricas,
E.I., Departament Mechanico,
Apartado Postal475, 62500 Cuernavaca, Mexico
V. EBERT Physikalisch Chemisches Institut,
Universitiit Heidelberg,
Im Neuenheimer Feld 253, 69120 Heidelberg, Germany
R. FEHLE Lehrstuhl A fiir Thermodynamik,
Technische Universitiit Miinchen,
Arcisstr.21, 80290 Miinchen, Germany
P. GEBHARD Lehrstuhl A fiir Thermodynamik,
Technische Universitiit Miinchen,
Arcisstr.21, 80290 Miinchen, Germany
U.L. GLUCKERT Lehrstuhl A fiir Thermodynamik,
Technische Universitiit Miinchen,
Arcisstr.21, 80290 Miinchen, Germany
M. HAIBEL Lehrstuhl A fiir Thermodynamik,
Technische Universitiit Miinchen,
Arcisstr.21, 80290 Miinchen, Germany
*
DR. C. HERMAN Department of Mechanical Engineering,
Johns Hopkins University,
122 Latrobe Hall / 3400 N. Charles Street
Baltimore, MD 21218-2686, U.S.A.
DR. J. KLAS Lehrstuhl A fiir Thermodynamik,
Technische Universitiit Miinchen,
Arcisstr.21, 80290 Miinchen, Germany
VI
DR. B. KRUPPA Lehrstuhl A fur Thermodynamik,
Technische Universitat Munchen,
Arcisstr.21, 80290 Munchen, Germany
PROFESSOR Lehrstuhl A fiir Thermodynamik,
DR. F. MAYINGER Technische Universitat Munchen,
Arcisstr.21, 80290 Munchen, Germany
R. MEMMEL Lehrstuhl A fur Thermodynamik,
Technische Universitat Munchen,
Arcisstr.21, 80290 Munchen, Germany
PROFESSOR Institut fur Verfahrenstechnik,
DR. D. MEWES Universitat Hannover,
Callinstr.36, 30167 Hannover, Germany
DR. R. RENZ Institut fiir Verfahrenstechnik,
Universitat Hannover,
Callinstr.36, 30167 Hannover, Germany
DR. H. SANDNER Lehrstuhl A fiir Thermodynamik,
Technische Universitat Munchen,
Arcisstr.21, 80290 Munchen, Germany
PROFESSOR Lehrstuhl A fur Thermodynamik,
DR. J. STRAUB Technische Universitat Munchen,
Arcisstr.21, 80290 Munchen, Germany
DR. G. STRUBE Lehrstuhl A fur Thermodynamik,
Technische Universitat Munchen,
Arcisstr.21, 80290 Munchen, Germany
DR. B. VOGEL Lehrstuhl A fur Thermodynamik,
Technische Universitat Munchen,
Arcisstr.21, 80290 Munchen, Germany
PROFESSOR Physikalisch Chemisches lnstitut,
DR. J. WOLFRUM Universitat Heidelberg,
Im Neuenheimer Feld 253, 69120 Heidelberg, Germany
*
former assistants of Lehrstuhl A fiir Thermodynamik
Preface
Increasing possibilities of computer-aided data processing have caused a new
revival of optical techniques in many areas of mechanical and chemical en
gineering. Optical methods have a long tradition in heat and mass transfer
and in fluid dynamics. Global experimental information is not sufficient for
developing 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.
Here optical measuring techniques provide comprehensive and detailed
information. Its results also supply valuable evidence on the formation of
phase interfaces, on particle movement, or on the size distribution of droplet
swarms. By using the results of optical measuring techniques, not only is it
possible to improve computer programs to give a better description of physical
processes and a better adaption to the physical reality but also these optical
techniques are very sensitive touchstones for checking the grade of reliability
and the extent of general validity of computer programs.
On the other side, evaluating optical data, for example from a hologram,
from an interferogram, from Raman-spectroscopy, or from laser-induced
fluorescence signals, has become much faster. A few years ago it took hours
to evaluate an interferogram. The same work is done today by a computer
within seconds. But also the huge storage capacity of modern computers -
even of the PC type - was an important requirement for preparing the way
for the revival of optical methods.
VIII Preface
The book is intended to demonstrate the possibilities of optical measur
ing techniques - especially image-forming techniques - and to introduce the
processes of recording, reprocessing and electronically evaluating the data. It
is intended to inform the reader to such an extent that he can design and
construct simple experimental set-ups. For more difficult and highly sophis
ticated techniques he is referred to the specialist literature in the field.
Franz Mayinger
Table of Contents
Optical Probes - Potential and Applicability 1
1 Introduction 3
2 Applications and Potential 5
3 Introduction to the Schlieren and Shadowgraph Method 11
3.1 Survey . . . . . . . . . . . . . . . . . . . . . . . 11
3.1.1 Basic Principle of the Schlieren Method . 11
3.1.2 Principle of the Shadowgraph Method . 12
3.2 Optical Interrelations . . . . . . . . . . . . . . . 13
3.2.1 Refractive Index and Temperature Field 13
3.2.2 The Deflection of Light in an Inhomogeneous Medium
(Spatially Variable Refractive Index) 14
3.3 The Transport Relations for Heat . . . . . . . . . . . . . . . . 16
3.4 The Model Boundary Layer . . . . . . . . . . . . . . . . . . . 16
3.5 Calculation of the Light Deflection in the Thermal Boundary . 18
3.5.1 General Calculation of the Screen Coordinate yL(y0) 18
3.5.2 Localisation of the Screen Coordinates . . . . . . . . . 19
Holography and Holographic Interferometry 25
4 Fundamentals of Holography and Interferometry . . . . . . 27
4.1 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.3 Principle of Holography . . . . . . . . . . . . . . . . . . . . . 29
4.4 Simple Holographic Arrangement . 30
4.5 Holographic Interferometry . . . . . 34
4.5.1 Double Exposure Technique 35
4.5.2 Real-Time Method . . . . . 39
4.5.3 Evaluation of the Interferograms. . . . . . . . . 42
X Table of Contents
406 An Interference Method for Simultaneous Heat and Mass
Transfer 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 45
40 7 Comparison with Classical Methods 0 50
5 Holographic Interferometry 0 0 0 0 0 0 0 0 51
501 Introduction 0 0 0 0 0 0 0 0 0 0 0 0 0 0 51
502 Components of a Holographic Interferometer 0 51
50201 Light Source 0 52
50202 Optical Table 53
50203 Shutter 0 0 0 53
502.4 Beam Splitter 53
50205 Attenuation Filter 53
50206 Beam Expander 0 0 54
5020 7 Mirrors, Lenses 0 0 55
50208 Recording Materials 55
50209 Piezo Mirror 0 0 0 0 0 57
502010 Test Facility 0 0 0 0 0 58
503 Evaluation of Interferograms 0 59
50301 Theoretical Principles 59
50302 Conclusions 0 0 0 0 0 0 63
50303 Calculation of Temperature and Concentration Distri-
butions 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 64
503.4 Determination of the Local Heat Transfer Coefficient 65
5.4 Examples 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 65
5.401 Determination
of the Temperature Distribution in a Compact Plate
Heat Exchanger with Plain Fins 0 0 0 0 0 0 65
5.401.1 Description of the Test Section 0 0 0 0 65
5.401.2 Description of the Interferograms 0 0 0 66
5.402 Analysing Axisymmetrical Temperature Fields 0 67
505 Distinction of Holograms 0 72
6 Differential Interferometry 0 0 0 75
601 Introduction 0 0 0 0 0 0 0 0 75
602 Differential Interferometer 78
60201 Wollaston Prism (WP) 78
60201.1 Double Refraction 78
60202 Optical Setup of a Differential Interferometer 80
603 Evaluation of Interferograms 82
0
6.4 Useful Techniques 0 0 0 0 0 0 0 0 0 85
6.401 Beam Expansion 0 0 0 0 0 86
6.402 Use of a Wollaston Prism 87
6.403 Adjustment of a Differential Interferometer 0 87
6.4.4 Recording 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 88
Table of Contents XI
6.5 Features and Applications 88
7 Pulsed Laser Holography 91
7.1 Introduction . . . . . 91
7.1.1 The Holographic Image. 91
7.1.2 Types of Holograms. . . 93
7.1.3 Holography as an Optical Measurement Method 96
7.1.4 Historical Development of the Holography 96
7.2 Elements of Holography . . . . . . 98
7.2.1 Recording of Holograms . . 98
7.2.2 Holographic Reconstruction 101
7.2.3 Recording Materials . . . . 101
7.3 Optical Arrangement for the Pulsed Laser Holography 103
7.3.1 The Pulsed Laser . . . . . . . . . . . 104
7.3.2 Selection of the Optical Components . . 104
7.3.3 Adjusting the Holographic Camera . . . 106
7.4 Example of Application: Spray Characterization 107
7.4.1 Statement of the Problem . . . . . . . . 107
7.4.2 Visualization of the Spray Flow . . . . . 108
7.4.2.1 Single Pulsed Holograms for the Measurement
of the Spray Geometry, Drop Size and Drop
Distribution in the Injection Volume . . . . . 108
7.4.2.2 Double Pulsed Holograms for the Measure-
ment of Droplet Velocities and Trajectories 109
7.4.3 Results . . . . . . . . . . . . . . . . . . . 112
8 Evaluation of holograms by digital image processing 115
8.1 Introduction . . . . . . . . . . . . 115
8.1.1 Digitalization of a Picture . . . . . . 115
8.1.2 Grey Value Pictures . . . . . . . . . 116
8.1.3 Operations with Grey Value Images . 118
8.2 The Digital Image Processing System . . . . 123
8.2.1 Scanning of Holographic Images . . . 123
8.2.1.1 Scanning of In-Line Holograms . 124
8.2.1.2 Scanning of Off-Axis-Holograms . 125
8.2.2 Setup of the Digital Image Processing System 125
8.3 Image Processing of Holographic Reconstuctions . . . 127
8.3.1 Filtering Operations, Image Identification, and Focus-
ing Criteria . . . . . . . . . . . 128
8.3.2 Measuring Algorithms . . . . . . . . . . . . . 132
8.4 Evaluation of Single Pulsed Holograms . . . . . . . . 134
8.4.1 Spray Form (Spray Angle, Break-Up Length) 135
8.4.2 Drop Size and Drop Distribution 135
8.5 Evaluation of Double Pulsed Holograms . . . . . . . 139