Flame structure, experimental study

Partially premixed flames are formed when a rich mixture of fuel and oxidizer is injected into an oxidizer stream. Below a certain value of the equivalence ratio of the rich mixture, a flame structure involving a premixed flame in the vicinity of a diffusion flame exists. Several experimental studies of NO emission properties of partially premixed laminar [1-4] and turbulent [5-10] flames have been reported in the literature. The results from the most recent studies indicate that using an optimum level of partial premixing can reduce NO emissions. 

Vol 3(1966), pp C304 to C319, (Chronographs and other methods for determination of detonation velocities) 84) R.W. Woolfolk A.B. Amster, "Low-Velocity Detonations Some Experimental Studies and Their Interpretation , 12thSympCombsm (1968) (Pub 1969), pp 731-39 85)M.F. Zimmer, "Similarity Between Wave Structures of Gaseous and Liquid Low Velocity Detonations , Ibid, p 740 (Paper No 73 in Abstracts, pp 133-34). This material is published in Combustion Flame 12, 1-4(1968)... 

Three years later, Broida, Schiff, and Sugden59 took issue with the simple mechanism Kaufman had proposed. They presented experimental evidence, as well as calling attention to previous work, that proved that the radiation was highly structured. They postulated a more elaborate mechanism that involved two excited states of N02 (Fig. 4-7), which, they felt, explained all the data, including those from air afterglow, flames, and fluorescence studies... 

Of the other experimental methods which have been employed to investigate fast chain reactions at high temperatures, combustion studies in premixed gas flames have been the most generally useful. As with shock waves, profiles within the reaction zone of these flames are strongly dependent on the chemical processes governing the rate of energy release. As has been frequently demonstrated in the past, detailed examination of flame structure can yield significant amounts of kinetic information. 

An important additional restriction on flame structure studies of kinetics is provided by the practical problem of maintaining one dimensional flame stability over a wide range of compositions, which limits the ranges of fuel/oxidizer ratios and percentage dilution by inert additives accessible to experimental study. The advantages to the kineticist of freedom in the selection of these quantities has been stressed above. The choice of experimental conditions in flames is also limited by the direct relationship between flame temperature and initial composition. In the shock tube where heating is provided by an outside source, i.e., the shock wave, these two variables can be selected independently of one another. The instability problem with exothermic reactions in shock waves is of a different character from that in flames. 

In an experimental study of the combustion of a polymer material it is especially important to investigate all the stages in which phase and chemical transformations of the substance are taking place. The complete scheme of the combustion process could be deduced from the study of such characteristics as the morphological structure of the burning surface, the temperature distribution inside the combustion wave, the structure and concentration profiles of each individual-stage product, the heat liberation ant heat losses, the structural properties of the flame and the limitations on combustion stability [16]. 

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