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Show transportation of momentum, heat, and mass in the field including the flame. Thus, visualization of the phenomena closely related to the chemical reaction process and momentum, heat, and mass transportation, as well as flame behavior itself, is useful to understand combustion phenomena. In most of studies on combustion phenomena, visualization has been used to draw main conclusions. A key to reach reasonable conclusions would be a careful selection of visualization techniques, because each visualization technique has its particular advantages as well as disadvantages. Therefore, knowledge on the characteristics of visualization techniques must be indispensable for combustion researchers. Table 1 shows an example of classification of visualization techniques based on the phenomena which can be examined by an appropriate use of each individual technique. Table 1 Phenomena to be appropriately examined using individual visualization techniques. Direct photography Flame shape Still EE Movie EE Streak Optical methods Shadow EE Schlieren EE Interferometry E Spectroscopic methods Emission Absorption Rayleigh scat. * Raman scat. * LIF* Tracer methods Smoke* Hot gas stream Particles* Bubbles* EE: extremely effective, *: Tomographic images can Phenomena to be examined Flame Tempera. Conc. Velocity behavior distri. distri. distri. EE EE E EE E E: effective, be obtained. P P EE EE EE E P p P EE EE EE EE E P E P: possible P EE EE EE Flow field EE EE EE The simplest and traditional method to record the aspects of flames must be direct photography. Indeed, this method has been used to record the shapes and luminosity and/ or color distributions of flames on photographs and the flame behavior can be explored on the basis of the photographs. However, the information derivable from the images to be recorded is closely related to the characteristics of a recording system, which consists of a camera and a film or some other photosensi ti ve equipment photosensor. Ins tantaneous or average flame shapes can be recorded by varying exposure. If details of local phenomena are needed, a lens assembly for a microscope can be adopted. Similar ly, a high-speed camera, television camera, streak camera, or other specially prepared camera can be used to obtain images needed to examine the interested phenomena. The characteristics of films or magnetic tapes and 2 |