Laser Diagnostics

It is important to have reliable laser diagnostics, preferably on a shot-to-shot basis this is possible for a 10 Hz system. To characterise the temporal profile of the pulses, single-shot spectra and autocorrelation data can establish whether the laser pulses are Fourier-transform limited. For lasers with a sech profile, a product AvAtxO.32 should be achieved. It is also important to monitor the focal spot, its Airy disc and average intensity. Alternatively, a reasonable measure of the focused intensity can be obtained using Xe gas and the known threshold intensities for producing the various stages of ionization [12]. 

---

Ebert V, Schulz C, Voipp H R, Wolfrum J and Monkhouse P 1999 Laser diagnostics of combustion processes from chemical dynamics to technical devices Israel J. Chem. 39 1-24... 

Bechtel J H and Chraplyvy A R 1982 Laser diagnostics of flame, combustion products and sprays Proc. IEEE 70 658-77... 

R. M. Osgood, S. R. J. Bmeck, and H. R. Schlossberg, eds.. Laser Diagnostics and Photochemical Processingfor Semiconductor Devices, North-HoUand, New York, 1983. 

Because high quaHty, low cost, and optimum performance are required for spray equipment, improved analytical and experimental tools are iadispensable for increasing productivity ia many competitive iadustries. In most iastances, it is no longer adequate to characterize a spray solely on the basis of flow rate and spray pattern. Information on droplet size, velocity, volume flux, and number density is often needed and can be determined usiag advanced laser diagnostic techniques. These improvements have benefited a wide spectmm of consumer and specialized iadustrial products. 

Application of laser diagnostics to probe elementary reaction processes and the structure of flames. 

Here, selected, more established laser diagnostic techniques will only be briefly named with their principal area of application in combustion measurements, but not further described details on these and other methods can be found in the above-mentioned literature and references cited therein. Workhorse techniques in combustion diagnostics include Raman and Rayleigh... 

Eckbreth, A.C., Laser Diagnostics for Combustion Temperature and Species, 2nd ed., Gordon and Breach, United Kingdom, 1996. 

Kohse-Hoinghaus, K. et at. Combustion at the focus Laser diagnostics and control, Proc. Combust. Inst., 30,89,2005. 

Barlow, R. S., Laser diagnostics and their interplay with computations to understand turbulent combustion, Proc. Combust. Inst., 31,49,2007. 

CA Dunbar, AP Watkins, JF Miller. An experimental investigation of the spray issued from a pMDI using laser diagnostic techniques. J Aerosol Med 10 351-368, 1997. 

Anglos D., Couris S., Fotakis C., Laser Diagnostics of Painted Artworks Laser-Induced Breakdown Spectroscopy in Pigment Identification, Appl. Spectrosc. 1997 51(7) 1025. 

MOLECULAR DESORPTION FROM SOLID SURFACES LASER DIAGNOSTICS AND CHEMICAL DYNAMICS... 

The soot formation and its control was studied in an annular diffusion flame using laser diagnostics and hot wire anemometry [17, 18]. Air and fuel were independently acoustically forced. The forcing altered the mean and turbulent flow field and introduced coherent vortices into the flow. This allowed complete control of fuel injection into the incipient vortex shedding process. The experiments showed that soot formation in the flame was controlled by changing the timing of fuel injection relative to air vortex roll-up. When fuel was injected into a fully developed vortex, islands of unmixed fuel inside the air-vortex core led to... 

Eckbreth AC. Laser diagnostics for combustion temperatures and species. 2nd ed. Amsterdam B.V., Netherlands Gordon and Breach Publishers 1996. 

Eckbreth, A. C. 1996. Laser diagnostics for combustion temperature and species. Amsterdam Gordon Breach Science. 

W.G. Breiland, M.E. Coltrin, and P. Ho. Comparisons between a Gas-Phase Model of Silane Chemical Vapor Deposition and Laser-Diagnostic Measurements. J. Appl. Phys., 59 3267-3273,1986. 

I hope that this book will serve to describe the excitement of current research in this field and the promise of a close coupling between the laser diagnostics and the modelling and chemical kinetics studies. Thanks are extended to the many contributors and to the publishers, and especially to Judy Turner for her assistance in organizing the symposium and assembling this volume. 

Laser-based spectroscopic probes promise a wealth of detailed data--concentrations and temperatures of specific individual molecules under high spatial resolution--necessary to understand the chemistry of combustion. Of the probe techniques, the methods of spontaneous and coherent Raman scattering for major species, and laser-induced fluorescence for minor species, form attractive complements. Computational developments now permit realistic and detailed simulation models of combustion systems advances in combustion will result from a combination of these laser probes and computer models. Finally, the close coupling between current research in other areas of physical chemistry and the development of laser diagnostics is illustrated by recent LIF experiments on OH in flames. 

Spatially Precise Laser Diagnostics for Practical Combustor Probing... 

---