Hydrocarbon Nanoparticles Formed in Flames and Diesel Engines

Abstract

The formation of nanoparticles in laboratory hydrocarbon flames is reviewed in terms of particle morphology, chemical composition, and health hazards. The nascent nanoparticles in the nucleation mode have been widely reported in diverse laboratory flames, and are distinguished by their occurrence as singlet particles that form translucent images in transmission electron microscopy (TEM). Their sizes range from about 10 nm or more down to 2 to 3 nm, the limit of resolution of the TEM, and they possess a liquid-like quality. These particles are widely considered to be the precursor stage to the more readily observed carbonaceous aggregates consisting of chained primary particles that are opaque to the electron beam of the TEM. Nanoparticles sampled from the inverse diffusion flame and the particle effluent from diesel engines show a strong resemblance by GCMS analysis, and they contain many of the stabilomer PAHs and their isomers in the 200 to 302 atomic mass range. Many of these chemical species have high relative mutagenicities. Distinctive bimodal particle size distributions can be observed in both flame and engine samples. Recent TEM micrographs of diesel particulates show images of precursor-like nanoparticles, of as yet unknown chemical composition, that are formed in a diesel engine at many operating conditions.

Critical Assessment of Photoionization Efficiency Measurements for Characterization of Soot-Precursor Species

“…[28][29][30][31][32][33][34][35][36] Figure 1a and c show aerosol mass spectra of soot extracted from the premixed flame at a height above the burner (HAB) of 6 and 10 mm, respectively. The sampling line used for extraction of the samples yielding the signals presented in Fig.…”

“…[28][29][30][31][32][33][34][35][36] Explicit evidence suggesting the presence or absence of particular isomers is, however, lacking. Some studies have presented results, beyond just molecular masses, that are consistent with the generation of stabilomer species during combustion and pyrolysis of carbonaceous fuels.…”

Effect of Open Channel Filter on Particle Emissions of Modern Diesel Engine

“…It is suggested that they are carbonaceous particles formed during combustion. 20,21 Negative health effects of particle emissions [22][23][24][25] have driven stricter emission standards for diesel particulate emissions. More stringent traffic emission limits drive engine and vehicle manufacturers to utilize new technologies to reduce emissions.…”

“…The origin or composition of these nonvolatile particles in unknown, but it has been suggested that they are heavy HCs formed during combustion. 20,21 Effect of DOC ؉ POC on Particles When the engine was equipped with the DOC ϩ POC combination, no nucleation-mode particles were detected at any of the four load points. This is shown in Figure 3, where the size distributions measured with and without the thermodenuder are shown.…”

Flame-Formed Carbon Nanoparticles: Morphology, Interaction Forces, and Hamaker Constant from AFM

“…Nascent carbon nanoparticles with equivalent diameter of about 2-4 nm are generated both in sooting conditions, where they coexist with larger primary soot particles and soot aggregates, and in less fuel-rich bluish flame conditions where they are formed alone or coexist with the larger 4-10 nm particles (Maricq 2004(Maricq , 2005Dobbins 2007;Commodo et al 2015). Nascent particles were reported to be liquid-like or bidimensional structures which assume an atomically thin disk-like shape when deposited on a substrate Dobbins 2007;Abid et al 2008;Minutolo et al 2014). Gas-phase precursors of freshly nucleated nanosized particles have been identified in polycyclic aromatic hydrocarbons (PAHs) (Ricther et al 2005; D'Anna 2009).…”