Combustion at the focus: laser diagnostics and control
Introduction
From the beginning of fire research, visible flame emission, spectroscopic flame signatures, and high-speed photography have proven useful to understand combustion phenomena. These early optical diagnostic techniques have been revolutionized by the use of modern laser technology. Today, visualization and quantitative measurements of important combustion parameters, such as concentration, temperature, velocity, rate of heat release, and pollutant emission, are common tools of the combustion scientist and engineer. Laser diagnostic measurement techniques make use of a large number of sophisticated instruments, providing continuous or high-speed measurements with high spatial resolution, flow-stopping interrogation times, and advanced strategies for quantitative calibration. Light, or more generally, electromagnetic radiation, is the only way to “spy” on the fundamentals of combustion inside the chemically active flame front. Modern laser-based diagnostics permit the study of combustion, even in the interior of engines, gas turbines, and large-scale combustors. Often, results from these measurements are combined with numerical simulation to improve the combustion process, based on a more detailed understanding of individual facets. Also, laser techniques are now used in combustion control. This article is not so much devoted to the description of these diagnostic methods and highly sophisticated experimental approaches, but rather is intended to highlight diagnostic methods and applications that have contributed to the fundamental knowledge of combustion chemistry, to the understanding and modeling of reacting flows, and to the improvement of practical combustion machinery.
Section snippets
Systems
The needs and challenges for optical diagnostics cannot be reviewed independent of the specific combustion systems, and the pertinent scientific and technical questions to be addressed. Combustion diagnostics are applied in devices as diverse as Bunsen flames and full-size power plants. Since the early International Combustion Symposia, optical diagnostic techniques—at these early meetings mainly high-speed photography, Schlieren images, and flame emission—have been used, driven by the wish to
Methods of optical combustion diagnostics
Optical diagnostic techniques rely on the interaction of electromagnetic radiation with the atoms, molecules, clusters, particles, and droplets present in a flame. Depending on the nature of this interaction, different properties may be probed. Quantities of interest include temperature, velocity, concentrations of major and minor constituents, and their local gradients or spatial and temporal variations. The wish list for diagnostics also includes quantities such as concentration and size
Examples of application of optical diagnostics to combustion problems
Combustion diagnostics have been used to study almost every combustion situation. Regarding the multitude of related investigations, it is not possible to provide a balanced and exhaustive review of the achievements of optical diagnostics in combustion, and it is similarly impossible to appropriately honor the work of all groups and individuals involved in these investigations. Rather, this article will be confined to illustrate some major avenues, and we have attempted to select some examples
Conclusions and perspectives
In future, further economic growth will be closely linked to an extensive use of combustion processes for mobility, energy conversion, and generation of industrial process heat. The limited supply of fossil fuels and the detrimental environmental effects of the global use of combustion, however, require pollutant emission to be minimized and total energy conversion efficiency and process performance to be optimized. Demands are similarly important for industrial combustion-based production
Acknowledgments
We are indebted to many colleagues for sharing their ideas with us in the numerous discussions, which have accompanied writing this paper. This includes in particular Mark Allen, Burak Atakan, Brigitte Attal-Trétout, Bob Bilger, Andreas Brockhinke, Sébastien Candel, Robert Cheng, David Crosley, John Daily, John Dec, Pascale Desgroux, Olaf Deutschmann, Andreas Dreizler, Jim Fleming, Fred Gouldin, Ron Hanson, Werner Hentschel, Jay Jeffries, Alfred Leipertz, Peter Lindstedt, Mark Linne, Jorge
References (300)
Proc. Combust. Inst.
(1998)Prog. Energy Combust. Sci.
(1997)Prog. Energy Combust. Sci.
(1994)Prog. Energy Combust. Sci.
(1988)- et al.
Combust. Flame
(1979) - et al.
Proc. Combust. Inst.
(2002) - et al.
Chem. Phys. Lett.
(2003) - et al.
Appl. Phys. B
(2000) - et al.
Appl. Phys. B
(2001) - et al.
J. Chem. Phys.
(2002)
Int. Rev. Phys. Chem.
Faraday Discuss.
Appl. Phys. B
Chem. Phys. Lett.
Combust. Sci. Technol.
Proc. Combust. Inst.
Appl. Phys. B
Appl. Phys. B
Proc. Combust. Inst.
Combust. Flame
Proc. Combust. Inst.
Appl. Opt.
Combust. Flame
Proc. Combust. Inst.
Proc. Combust. Inst.
Proc. Combust. Inst.
Proc. Combust. Inst.
Proc. Combust. Inst.
Proc. Combust. Inst.
Proc. Combust. Inst.
Combust. Flame
Proc. Combust. Inst.
Combust. Flame
Proc. Combust. Inst.
Proc. Combust. Inst.
Proc. Combust. Inst.
Laser Diagnostics for Combustion Temperature and Species
Proc. Combust. Inst.
Appl. Opt.
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