5 years ago

chapter 5 turbulent diffusion flames - FedOA

chapter 5 turbulent diffusion flames - FedOA

d(N/NT)/dDP, cm -1

d(N/NT)/dDP, cm -1 d(N/NT)/dDP, cm -1 d(N/NT)/dDP, cm -1 1.E+07 5.E+06 1 5 9 0.E+00 13 17 21 25 29 0 2 4 6 8 10 12 14 D DP, P, P, nm Fig. 3.20 AFM normalized size distribution curve of particles sampled at z=5mm. The mean size calculated from AFM size distribution function is in close agreement with that obtained from scattering/extinction measurements. Concluding, the main results of this study of benzene combustion are: • high molecular mass structures with typical sizes of 3-4 nm are formed in the main oxidation region of the flame. • the higher concentration of nanoparticles in the C/O=0.72 flame and the radical-rich flame environment in which they are formed promote the dehydrogenation of nanoparticles increasing the level of their aromaticity. As a result, nanoparticles with typical sizes of about 5 nm, absorbing and fluorescing in the visible are formed in the slightly sooting flame. • visible absorbing nanoparticles reach a maximum concentration just before the appearance of mature soot particles and they can be considered responsible for soot formation. 78

According to the experimental results, inception of soot particles in benzene flames consists in the progressive aromatization of initially “transparent” structures, followed by coagulation of visible absorbing nanoparticles to form soot. This picture is different to that found in aliphatic fuel flames where the aromatization process which precedes coagulation has never been observed. 79

DNS of Turbulent Nonpremixed Ethylene Flames
Heat release rate measurement in turbulent flames