Flame mechanisms

Candle and Jet Diffusion Flames Mechanisms of Combustion under Gravity and Microgravity Conditions... 

Of course, the complete flame mechanism must include... 

The so-called diffusion theories of flame propagation, as exemplified by the work of Tanford and Pease 38), emphasize the transport of mass, in that concentration of an active radical is assumed to be the rate-controlling property. Its use seems to be fairly limited in that only a few specific reactions have been successfully studied with this theory. What is more interesting, however, is that this theory forms the counterpart to the thermal theory. These two extreme views bracket the actual case, and their study allows a consideration of each of two of the basic flame mechanisms, unencumbered by the other. Actual deflagration depends on both the transport of heat and the transport of mass, and a successful theory should contain both phenomena. 

Does the proposal introduce a source of ignition (including hot surfaces, flame, mechanical sparks, static electricity, electrical arcing, etc.) ... 

It is well known that good flame velocity results do not mean that the chemical mechanism is correct. Similarly, lists of reactions with high flame velocity sensitivity do not show all the important parameters of a flame mechanism. Tuning of rate parameters having high-flame velocity sensitivities would alter significantly the flame propagation speed, but there are other parameters in the mechanism which have to be known precisely for the calculation of realistic concentration vs. distance profiles. 

The starting point in development of an ammonia flame mechanism was a mechanism previously used to model ammonia oxidation in a flow tube near 1300 K ( ). Additional reactions were added that were thought to be important at the higher flame temperatures. Calculations with this mechanism produced profiles in marked disagreement with our data. The predictions were slower than observed decay of NH species was much too slow, and OH peaked too late by about 2.5 mm. To make matters worse, far too much NO was formed. The NO problem was especially troublesome in that attempts to increase the rate of NH decay only served to produce even more NO, since NO was the primary decay channel for the NHi species. A possible resolution of this dilemma involves reactions of the NHi species with each other to form N-N bonds. These complexes could then split off H atoms to ultimately form N2. 

TAK 09] Takahashi F., Candle and jet diffusion flames mechanisms of combustion under gravity and microgravity conditions , in JAROSINSKIJ., VEYSSifiRE B. (eds.). Combustion Phenomena, CRC Press, Boca Raton, pp. 170-178, 2009. 

Possible flaming mechanisms of frame-retardant PP composites are shown in Figure 3. Flame-retardant might be adsorbed onto talc surface, because talc and flame-retardant were in base and acid, respectively. Total surface area of talc increased when talc content was increased or smaller talc was incorporated. Hence, more flame retardant was adsorbed onto talc and the flame-retardancy decreased, when large amount of talc or smaller talc was blended. Another possible explanation is that talc plays role of acceleration of diffusion to combustible gas. PP is melting phase like wax in flaming combustion. Hence, talc can act as wick of candle. A candle is noncombustible if it doesn t have a wick. 

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