Flame production

NO is formed to some extent from N2 and O2 in flame products when N atoms are produced at a significant rate. Above 1700 K, the important step in the much studied Zeldovitch (thermal) mechanism is the production of N atoms by ... 

When [NO] temperature dependence, an activation energy of 316 kj/mol (75.5 kcal/mol). Unfortunately, the rate becomes appreciable just in the range of typical hydrocarbon—ak flame conditions. If it is also assumed that [O] = [O], the observed rate in most lean-flame products in which N2 is roughly 75 mol % of the gas can be approximated by... 

The composition, properties, and size of soot particles collected from flame products vary considerably with flame conditions and growth time. Typically the C—H atomic ratio ranges from two to five and the particles consist of kregular chains or clusters of tiny spheres 10—40 nm in diameter with overall dimensions of perhaps 200 nm, although some may agglomerate further to much larger sizes. 

It is interesting to note that stratified combustible gas mixtures can exist in tunnel-like conditions. The condition in a coal mine tunnel is an excellent example. The marsh gas (methane) is lighter than air and accumulates at the ceiling. Thus a stratified air-methane mixture exists. Experiments have shown that under the conditions described the flame propagation rate is very much faster than the stoichiometric laminar flame speed. In laboratory experiments simulating the mine-like conditions the actual rates were found to be affected by the laboratory simulated tunnel length and depth. In effect, the expansion of the reaction products of these type laboratory experiments drives the flame front developed. The overall effect is similar in context to the soap bubble type flame experiments discussed in Section C5c. In the soap bubble flame experiment measurements, the ambient condition is about 300 K and the stoichiometric flame temperature of the flame products for most hydrocarbon fuels... 

A lance is a hrework that is about the size of a small pencil that functions in the manner of a flare (Figure 10.3). Thus, the theory of coloured flame production, as presented in Chapter 8, applies equally to the lance. 

B. E. Douda, Theory of Coloured Flame Production , U.S. Naval Ammunition Depot, RDTN No. 71, 1964. 

A more general treatment that applies readily to homogeneous and heterogeneous equilibria alike was developed by von Stein (Ref 11a). It was originally formulated to facilitate computations by desk computer of isobaric multicomponent flame product compns, but has been adapted at PicArsn to the calcn by electrical analog computer of isochoric expln products... 

The hot, partly combusted gases then come into contact with oxygen from the air and the final flame products are formed. This occurs in what is known as the secondary reaction zone or diffusion zone. This discussion refers to premixed gas flames with laminar (i.e. non-turbulent) flow of the gas mixture to the flame. 

There are three principles by which a flame process may be designed. A flame may form a desirable product by reacting to a favorable equilibrium state. The stabilization of an intermediate species may be achieved by quenching. Finally, the condensation of solids from flame products may be controlled to give desirable physical properties to the solids. 

The only condition for cool-flame production with ethanol was that the temperature at the centre of the vessel rose above the ambient by a critical amount, about 20 °C. This suggests that thermal factors are important in cool-flame production, and this was confirmed by the effect of addition of inert gases. The special importance of thermal conductivity is exemplified by the differing effects of helium and xenon, two gases with identical heat capacities but very different thermal conductivities. Thus helium raised the limit, while xenon lowered it. 

A distinction in the applicability of results must be made between isothermal and non-isothermal experimental investigations of hydrocarbon oxidation. Whilst the latter provide useful qualitative insight into variations in product distributions, they do not give satisfactory quantitative data, especially with regard to combustion during cool-flames. Product yields... 

Diminishing the Flame Production of Explosives , GerP 2530656 (1976) CA 85, 7959 (1976) [The inventor suggests that addn of a cationic ion resin charged vnth enough alkali metal cations to create a neutral reaction in aq soln suppresses flame formation in a doublebase proplnt. Thus, no flame is observed from a compn con NC 89.5, NG 5, DPA 1, DNT 1.5 and TNT 1.5p, to which 1.5p of Lewasorb AlO has been added after activation with K ions]... 

Burning is not well defined it is a relatively low rate combustion reaction that looks like burning . (There is flame production but no pressure effects.)... 

Sodium is a very strong atomic emitter of yellow light. Thus, the use of a sodium salt is about all that is necessary to produce a fairly good yellow flame. None of the subtleties of other colored flame production are necessary (e.g., color enhancers, flame temperature, etc.). 

In compiling a list of compositions for colored flame production, formulas have been taken from specifications for certain items and a number of such formulas could be found in a rather unusual source, i.e, a manual on the toxic hazards of pyrotechnic items. Others have come from the writer s notebooks, a few from patent disclosures or from special reports. Since there is now little overlapping between the formulas for ordnance items and for fireworks, the latter, which are appended to the following chapter, arc only of passing interest to the designer of military flares and stars. 

The other approach is to embed the hygroscopic perchlorates in a plastic material, which thus becomes fuel, binder, and protective coating and also opens the way for new production techniques. This scheme has been tried as shown in a U. S. patent for lithium perchlorate embedded in nylon for the purpose of formulating high-energy propellants, and it is applicable to colored flame production. A similar idea is incorporated in another U. S. patent that deals with colored flame matches or more exactly match splints made from cellulose acetate in which the perchlorates of copper or strontium perchlorate, dissolved in triethanolamine, are dispersed. Again, the color effect is most pleasing, but the technique seems to have remained confined to laboratory samples. 

We must now return to the less esoteric aspects of colored flame production. A practical approach is the use of the nitrates of barium and strontium as oxidizers followed by their partial conversion into halides by combining them with the oxidizers potassium chlorate or perchlorate. Eliminating the chlorate for military purposes because of... 

B. Douda, NAD, Crane, Ind., Theory of Colored Flame Production, RDTN No. 71, 20 March 1964. 

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