Search

The oxidation rates of diesel soot from the combustion chamber of a running diesel engine were calculated based on the particle size distributions at different crank angles. The primary particle diameter and nanostructure of soot were obtained by means of high-resolution transmission electron microscopy (HRTEM). The soot characteristics were also investigated by oxidative thermogravimetry and Raman scattering spectrometry. The results showed the soot nanostructures were dependent on engine operation conditions and combustion phases. The oxidation rates were found to differ by nearly fourfold from that calculated by the Nagle/Strickland-Constable (NSC) model for the soots studied here. The varied oxidation rates were interpreted in terms of differences in nanostructure between the soots. The experimental results were used to modify the NSC model and the fringe length of in-cylinder diesel soot was chosen to describe the influence of graphitisation on the oxidation of soot. The modified NSC model lessened the deviation between measurements and predictions. [ABSTRACT FROM AUTHOR]

This work studied the evolution of in-cylinder polycyclic aromatic hydrocarbons (PAHs) in a diesel engine fueled with n -heptane, and explored the effects of adding toluene to n -heptane on in-cylinder PAHs. In-cylinder PAHs were sampled in a direct injection diesel engine using a total cylinder sampling system. PAHs were analyzed by gas chromatography–mass spectrometry with programmed temperature vaporization in the solvent vent mode. For n -heptane, the mass of total in-cylinder PAHs ( Σ M PAHs ) increased in premixed and late diffusion combustion phases, and decreased in early diffusion and late combustion phases. Among the 16 PAHs detected, Naphthalene (Nap) was the most abundant. PAHs with two benzene rings and one five-membered ring, such as Acenaphthylene, Acenaphthene and Fluorene, were also plentiful, implying that PAHs with five-membered ring could play an important role in the growth of in-cylinder PAHs. When adding 20 vol.% toluene to n -heptane, the evolution of ΣM PAHs was varied. The Σ M PAHs for n -heptane/toluene increased in premixed and early diffusion combustion phases, and decreased in late diffusion and late combustion phases. Toluene addition reduced the ΣM PAHs in the premixed combustion phase by up to 48% but increased ΣM PAHs by 30% in the early diffusion combustion phase. In the subsequent combustion phase, the ΣM PAHs was reduced by approximately 67%. For in-cylinder individual PAHs, toluene addition generally reduced the percentages of Nap in ΣM PAHs during the engine combustion process but increased the percentages of larger PAHs, indicating that toluene addition was conducive to the growth of PAHs to form larger PAHs. [ABSTRACT FROM AUTHOR]

Highlights: [•] Reductions in CBC emissions were assessed for CFT diesel. [•] Significant reductions in emissions of total and individual CBCs were obtained. [•] The percentage reduction in the total CBCs decreased with an increase in engine load. [•] The percentage reduction in the total CBCs increased with increase in engine speed. [•] The ozone formation potential of CBCs emitted was strongly reduced with use of CFT. [ABSTRACT FROM AUTHOR]

The study made investigation on the combustion, performance and emissions of a modern dual fuel (DF) diesel engine using silicon dioxide (SiO 2) nanoparticle additives to methanol under different test conditions. The tests were conducted in three operating modes: diesel mode; methanol/diesel mode (methanol mode for short) and methanol-based SiO 2 nanofluid (MSN)/diesel mode (MSN mode for short) where the MSN was injected in the intake manifold. The results displayed that nano-SiO 2 inclusion in methanol increased the peak pressure by 8.6% in maximum and peak heat release rate by 4.3% in maximum. The brake thermal efficiency (BTE) and brake specific fuel consumption (BSFC) were improved with all the tested dosages of SiO 2 nanoparticles in the fuel, especially under high load conditions, the improvements of 5.1% in maximum and 6.2% in maximum for BTE and BSFC were achieved. Compared with the cases in methanol mode, CO, HC, NO x and smoke opacity in MSN mode were reduced by 38.5%, 55.4%, 5.2% and 55.6%, respectively. All the results indicate that the addition of SiO 2 nanoparticle in methanol could enhance the combustion and performance characteristics, and suppress the emissions of the DF diesel engines. • Nano-SiO 2 addition increases HRRmax and Pmax, especially at high engine load. • SiO 2 nanoparticles cause obvious ignition and combustion duration improvements. • Nano-SiO 2 additives in methanol increase BTE and lessen BSFC. • SiO 2 nanoparticles suppress significantly CO, HC, NO X and smoke emissions. [ABSTRACT FROM AUTHOR]

Abstract: The diesel soot was extracted from the chamber of a running diesel engine using a total cylinder sampling system. A structural description and size distribution of the soot spherules were performed by means of high-resolution transmission electron microscopy (HRTEM). HRTEM image analysis was carried out to achieve semi-quantitative information about the soot organization. Different nanostructures were found in dependence upon the engine test conditions. A better organization of the graphitic layers occurred for the in-cylinder soot as the expansion stroke developed. The oxygen concentrations at sampling angles and the cylinder pressure were measured. The oxidation rates of the in-cylinder soot during the late combustion phase were calculated according to the differences of spherules size distributions between two consecutive sampling angles. The soot reactivity in dependence on the nanostructure was shown after deducting the effect of oxygen concentration and temperature. The increase of resistance toward oxidation was associated to the increase of the structural order for the in-cylinder soot. The results are a useful database for testing the structure–property relationship between the nanostructure and the reactivity of the in-cylinder diesel soot. [ABSTRACT FROM AUTHOR]

• The presence of nano-CeO 2 in methanol increased peak HRRmax and Pmax. • Nano-CeO 2 additives promoted a shorter ignition delay and combustion duration. • Nano-CeO 2 additives in methanol increased BTE and lessened BSFC and EGT. • Nano-CeO 2 inclusion in methanol can suppress CO, HC, NO X and smoke emissions. This paper signifies the effects of cerium oxide (CeO 2) nanoparticles on the combustion, performance and emissions characteristics of a dual fuel diesel engine under different loads. The stable methanol-based nanofluids with the dispersion of 25 ppm and 100 ppm of CeO 2 nanoparticles fuels (MCN25 and MCN100) were prepared by ultrasound and surfactant. The tests were conducted on a dual fuel diesel engine under three modes: diesel mode, by injecting diesel alone into the cylinder; methanol mode, with methanol intake manifold injection and diesel direct injection; and MCN mode, with MCN fuels intake manifold injection and diesel direct injection. The results show that the peak heat release rate and the peak cylinder gas pressure in MCN mode are increased by 7.9% and 4.3% compared to those of diesel mode. Compared to methanol mode, the engine operated in MCN mode effectively reduces brake specific energy consumption by a maximum of 8.1% and increases brake thermal efficiency by up to 10.8%. Further, the increased HC and CO emissions in methanol mode (compared to diesel mode) are suppressed effectively when adding CeO 2 nanoparticles in methanol, with the maximum reductions of 56.3% and 79.8% in HC and CO emission for the dosage of 100 ppm, respectively. Compared with diesel mode, the engine operated in methanol mode can decrease the NO X emission and smoke opacity, while more significant reductions can be observed with the addition of CeO 2 nanoparticles in methanol, with the maximum decreasing results of 70.9% and 90.3%. [ABSTRACT FROM AUTHOR]