Flames acetylene-oxygen

In low pressure flames, however, the situation is less clear cut (9). For example, in stoichiometric acetylene-oxygen flames at 1.0 torr (T = 2500°K.) the value of k required to explain the experimental data can be calculated by equating the rate of OH - formation at the steady state to the appropriate loss rate, which must include diffusion ... 

Figure 1. Positive ion profiles in an acetylene/oxygen flame...

In a lean acetylene/oxygen flame, C2H30 + is, in fact, the dominant ion, its concentration exceeding even the maximum H30+ concentration (9). It is presumably produced by Reaction 19. 

Flame background spectrum of an acetylene -oxygen flame containing an organic aerosol. 

Emission intensity of sodium in the acetylene-oxygen flame at 589 nm showing the effect of self-absorption on calibration curves. 

Another process involves molecular aggregation by means of direct chemical reactions akin to polymerization. The best known example of this is the process of carbon particles in a premixed acetylene-oxygen flame. Evidently particle formation in this case does not involve condensation from a supersaturated vapor, but proceeds directly through the pyrolysis of the acetylene, forming in the process unstable polyacetylenes as intermediates in the flame. 

N.G. Glumac and D.G. Goodwin, Diagnostics and Modeling of Strained Fuel-Rich Acetylene/Oxygen Flames Used for Diamond Deposition, Combustion... 

Although all of the techniques described above were apphed in acetylene-oxygen flames at 20 mm Hg, experimental diflBculties prevented their apphcation to the same conditions of fuel equivalence (<>) and cold gas velocity (v). 

Figure 1. Number concentrations of species in sooting acetylene/ oxygen flames as a function of height above the burner for different fuel equivalence ratios () and cM gas velocities (v). Pressure = 20 mm Hg points = experimental data curves = estimated trends, (a) Total soot particles (b) charged soot particles = 3.0, v= 50 cmisec, Wersborg (7) (c) targe positive ions = 3,0, v = 38 cm sec, Yeung (9) (d) and (e) total positive ions, different assumed species sizes (see text), = 3,5, v = 50 cmisec. Frier (S),...

Figure 2, Volume concentration of heavy hydrocarbon molecules and soot at different heights above the burner in an acetylene/oxygen flame. Pressure = 20 mm Hg fuel equivalence ratio = 3.0 cold gas velocity = 50 cm sec.

Radicals.—The measurement of emission intensities from electronically excited small free radicals has become an important means of determining radical concentrations in hostile environments such as flames. When combined with laser excitation, the technique is very powerful, offering temporal, spectral, and spatial resolution. Just has reviewed laser techniques for the measurement of both radical concentrations and local temperatures in flames, and has demonstrated the use of laser-induced saturated fluorescence to measure the concentrations of CH and OH radicals in low-pressure acetylene-oxygen flames. Vanderhoff ei al. used a novel Kr " and Ar laser intracavity technique to... 

Chrysene occurs as a product of combustion of fossil fuels and has been detected in automobile exhaust. Chrysene has also been detected in air samples collected from a variety of regions nationally and internationally. The concentrations were dependent on proximity to nearby sources of pollution such as traffic highways and industries, and was also dependent on seasons (generally higher concentrations were noted in winter months). Chrysene has also been detected in cigarette smoke and in other kinds of soot and smoke samples (carbon black soot, wood smoke, and soot from premixed acetylene oxygen flames). It has been detected as a component in petroleum products including clarified oil, solvents, waxes, tar oil, petrolatum, creosote, coal tar, cracked petroleum residue, extracts of bituminous coal, extracts from shale, petroleum asphalts, and coal tar pitch. 

In the boat technique, the liquid sample is deposited in a narrow, boat-shaped container and carefully dried. The container is made of tantalum or other high-melting-point metal. The boat is placed under the light path of the hollow cathode lamp and the dried sample is vaporized by electrical heating or with a conventional acetylene-oxygen flame. This technique, although simple, is not free from interferences and offers better sensitivity for a few elements only. 

Tubular crucibles made of Itythagoras mass may be closed off in the same way as an ampoule, that is, by pulling to a small diameter and sealing the top end in a hydrogen-oxygen or acetylene-oxygen flame (see ampoule methods, p. 1782). 

Ion Concentrations in Premixed Acetylene-Oxygen Flames near the Soot Threshold... 

Total ion concentration profiles were measured through the flame front of laminar, premixed, low pressure acetylene-oxygen flames at equivalence ratios, <(), from... 

Acetylene-oxygen flame near soot threshold... 

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