Volatility characterization of nanoparticles from single and dual-fuel low temperature combustion in compression ignition engines

Abstract

This work explores the volatility of particles produced from two diesel low temperature combustion (LTC) modes proposed for high-efficiency compression ignition engines. It also explores mechanisms of particulate formation and growth upon dilution in the near-tailpipe environment. The number distribution of exhaust particles from low-and mid-load dual-fuel reactivity controlled compression ignition (RCCI) and single-fuel premixed charge compression ignition (PPCI) modes were experimentally studied over a gradient of dilution temperature. Particle volatility of select particle diameters was investigated using volatility tandem differential mobility analysis (V-TDMA). Evaporation rates for exhaust particles were compared with V-TDMA results for candidate pure nalkanes to identify species with similar volatility characteristics. The results show that LTC particles are mostly comprised of material with volatility similar to engine oil alkanes. V-TDMA results were used as inputs to an aerosol condensation and evaporation model to support the finding that smaller particles in the distribution are comprised of lower volatility material than large particles under primary dilution conditions. Although our results show that saturation levels are high enough to drive condensation of alkanes onto existing particles under the dilution conditions investigated, they are not high enough to allow homogeneous nucleation of these same compounds in the primary exhaust plume. Therefore, we conclude that observed particles from LTC operation must grow from low concentrations of highly nonvolatile compounds present in the exhaust. EDITOR Matti Maricq

Size and volatility of particle emissions from an ethanol-fueled HCCI engine

“…Homogeneous nucleation of hydrocarbons occurs at much higher concentrations than required for sulfuric acid. Similar work in a low temperature combustion system concluded hydrocarbon concentrations were too low for homogeneous nucleation and suggested that unknown, very low volatility species are responsibility for nucleation (Lucachick et al 2016). This is consistent with other findings that other low volatility hydrocarbons, not found in lubricating oil but potentially formed when subjected to high temperature cylinder conditions, such as organic acids, impact nucleation (Arnold et al 2012).…”

Gaseous emissions and particle size distribution of dual-mode dual-fuel diesel-gasoline concept from low to full load

“…Prikhodko et al [33] found that RCCI was highly dominated by nucleation mode particles. Several studies confirm that RCCI produces lower number of particles amongst other LTC strategies [34] [35]. Kolodziej et al [36] also studied the effects of the diesel proportion and the injection timings in the particle size while operating under RCCI.…”

Effects of multiple injection strategies on gaseous emissions and particle size distribution in a two-stroke compression-ignition engine operating with the gasoline partially premixed combustion concept

“…However, a slight increase in accumulation-mode particles was observed while the nucleation-mode particles decreased, approximately in the same proportion, with the SoE2 advance. As previously analyzed, the SoE2 advance reduces the mixing time, facilitating the carbonaceous particles formation (accumulation-mode) and consequently provides a large surface area for adsorption of the volatile condensates, 49,50 decreasing the concentration of nucleationmode particles.…”

“…In this case, the nucleation mode is promoted against the accumulation mode due to the low absorption of volatiles that can take place on the surface of the carbonaceous particle under these conditions. 49,50 The changes in the accumulation mode can be observed in the particle mass scale, as the PN is so low that the variation cannot be clearly observed in the number scale. In the nucleation mode, a slight increase in PN emissions was observed with the decrease in IP, without significant shifts of the PSDs to larger sizes.…”