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Combination of Optical Methods for Studies in Combustion and Wave Propagation 2006:01 DOCTORAL T H E SI S Combination of Optical Methods for Studies in Combustion and Wave Propagation Roger Mattsson Luleå University of Technology Department of Applied Physics and Mechanical Engineering Division of Experimental Mechanics 2006:01|: 102-1544|: - -- 06⁄01 -- Combination of Optical Methods for Studies in Combustion and Wave Propagation Roger Mattsson Division of Experimental Mechanics Department of Applied Physics and Mechanical Engineering Luleå University of Technology SE-971 87 Sweden Luleå 2005 Keywords: Pulsed TV holography, Schlieren, Laser Doppler Vibrometry, Transient events, Combustion, Flames, Bending wave propagation, Non-destructive testing, Acoustic wave propagation i ii Preface The work contained in this thesis was carried out during the years 2000-2005 at the Division of Experimental Mechanics, Luleå University of Technology (LTU), Sweden. The Swedish Research Council (VR) is gratefully acknowledged for their support in this project. I would like to thank my supervisors at LTU, Associate Prof. Anders Wåhlin and Dr. Per Gren, as well as the former and the present Heads of our Division Prof. Nils-Erik Molin respectively Prof. Mikael Sjödahl. My supervisors introduced me to the field of holographic interferometry and gave me professional guidance and support. Their broad knowledge, experience and enthusiastic working attitudes are highly appreciated. They have contributed much of this work by providing good advice and suggestions, and by critically examining the performed projects. Further, they are also co-authors of most of the appended papers. The other co-authors are hereby thanked, in alphabetic order of their family name: Torgny Carlsson1, Mattias Elfsberg1, Christer Fureby1, Karl-Evert Fällström2, Marco Kupiainen3 and Jon Tegner1. Of these persons, a special thank goes to Torgny Carlsson for a fruitful co-operation, his hospitality, arrangements and help with transport during our visits to FOI-Grindsjön, Stockholm. Further, I am grateful for the extensive work of Bengt Eiderfors1 and Torgny on planning and thereby allowing our cooperative experiments at FOI-Grinsjön to be performed. Although we carried out these experiments with short time frames and the occurrence of all kinds of annoying and sometimes unexpected problems, Torgny has always maintained a positive and optimistic attitude. All my colleagues at the Division of Experimental Mechanics are hereby thanked for making my time here very interesting and enjoyable. Friends, who have enlightened my spare time with, e.g. exciting hunting and fishing adventures, are of course specially thanked. Finally, I would like to express my deepest gratitude to my beloved Karin and our wonderful daughter Sally for their support and encouragement. Without you, I would not have been able to accomplish this work. Since my daughter cannot read yet and would probably be bored by just looking at the text, I take the liberty of including a photograph of her. Roger Mattsson Luleå, December 2005 Figure ȱ. Sally Mattsson. 1 The Swedish Defence Research Agency, FOI-Grinsjön, Stockholm. 2 Division of Experimental Mechanics, Luleå University of Technology. 3 The Royal Institute of Technology, Stockholm. iii iv Abstract In this thesis, different optical methods were combined for studies of combustion processes in gases and transient wave propagation in plates and water. Pulsed TV holography was used in all these projects. In three of the five appended papers, the pulsed TV holography technique was compared and combined with the schlieren or the Laser Doppler Vibrometry (LDV) technique. Three investigations of combustion processes were performed. A turbulent propane-air jet diffusion flame was investigated using pulsed TV holography and schlieren. From Large Eddy Simulations (LES) of a model describing the flame dynamics, a refractive index field of the process was calculated. The actual experiment was simulated by ray-tracing through the numerically calculated refractive index field. Comparing this result to the corresponding experimental data allowed the model to be validated. Further, the ignition of pre-mixed propane gas was studied with pulsed TV holography. The ignition of the gas was initiated by a focused laser pulse from the same laser used for the recording of the digital holograms. The position of the flame front at different time instants could be determined. In addition, differences in refractive index between a flowing gas and ambient air could be determined in situ. Finally, the propagation of a high-speed turbulent flame jet of a stoichiometric air-hydrogen gas mixture inside a rig was studied using schlieren and pulsed TV holography. The latter method was used to calibrate the schlieren images for quantitative measurements. A theory that takes tensile forces into account for anisotropic plates subjected to an impulsive load was expanded to include paper sheets subjected to tensile forces as in real papermaking machines. Matching this solution to experimentally obtained interferograms using pulsed TV holography showed that material parameters of the paper sheets, such as stiffness and anisotropy in various directions, could be determined from the recorded bending waves. Studies of propagating bending waves in an impact-loaded aluminium plate of water-filled box and acoustic waves in the water were performed using pulsed TV holography and LDV. The results indicate that both methods are supplementary in wave propagation measurements, since pulsed TV holography provides high spatial resolution and LDV gives high temporal resolution. In conclusion: To investigate complex processes, e.g. combustion, different methods are required. Numerical models must be validated by experiments for reliability, often with a combination of supplementary methods. An iterative process between experiments and numerical modelling will result in an increased understanding of the physical phenomena involved. v vi Thesis This thesis comprises a survey and the following five appended papers: Paper A K.-E. Fällström, P. Gren and R. Mattsson, ”Determination of paper stiffness and anisotropy from recorded bending waves in paper subjected to tensile forces,” NDT&E International, 35, pp. 465-472, 2002. Paper B R. Mattsson, M. Kupiainen, P. Gren, A. Wåhlin, T. Carlsson and C. Fureby, “Pulsed TV holography and schlieren studies, and large eddy simulations of a turbulent jet diffusion flame,” Combustion and Flame, 139 (1-2), pp. 1–15, 2004. Paper C R. Mattsson, P. Gren and A. Wåhlin, “Laser ignition of pre-mixed gases studied by pulsed TV holography,” Proceedings of SPIE Vol. 4933, Speckle Metrology, June 18-20 2003, Trondheim, Norway. Paper D T. Carlsson, R. Mattsson, P. Gren, M. Elfsberg and J. Tegner, “Combination of schlieren and pulsed TV holography in the study of a high-speed flame jet,” accepted for publication (28 May 2005) in Optics and Lasers in Engineering. Paper E R. Mattsson, “Bending and acoustic waves in a water-filled box studied by pulsed TV holography and LDV,” accepted for publication (21 October 2005) in Optics and Lasers in Engineering. vii viii Contents Preface .............................................................................................................iii Abstract.............................................................................................................v Thesis..............................................................................................................vii 1 Introduction....................................................................................................1 2 Transient events in combustion an mechanics ..............................................2 2.1 Combustion of gaseous fuels ..................................................................2 2.2 Bending waves and acoustic waves ........................................................3 3 Optical methods and examples of applications .............................................5 3.1 Pulsed TV holography.............................................................................5 3.1.2 Description and performance of a pulsed TV holography system ...6 3.2 The schlieren technique...........................................................................8 3.3 Laser Doppler Vibrometry ......................................................................9 3.4 Examples of applications ......................................................................11 4 Other optical methods..................................................................................14 4.1 Non-spectroscopic methods ..................................................................14 4.2 Spectroscopic methods..........................................................................15 5 Conclusions and future work.......................................................................17 6 Summary of appended papers .....................................................................19 7 References....................................................................................................23 Appended papers A Determination of paper stiffness and anisotropy from recorded bending waves in paper subjected to tensile forces B Pulsed TV holography and schlieren studies, and large eddy simulations of a turbulent jet diffusion flame C Laser ignition of pre-mixed gases studied by pulsed TV holography D Combination of schlieren and pulsed TV holography in the study of a high- speed flame jet E Bending and acoustic waves in a water-filled box studied by pulsed TV holography
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