Detailed characterization of particulate matter emitted by lean-burn gasoline direct injection engine

Abstract

This study presents detailed characterization of the chemical and physical properties of particulate matter emitted by a 2.0-L BMW lean-burn turbocharged gasoline direct injection engine operated under a number of combustion strategies that include lean homogeneous, lean stratified, stoichiometric, and fuel-rich conditions. We characterized particulate matter number concentrations, size distributions, and the size, mass, compositions, and effective density of fractal and compact individual exhaust particles. For the fractal particles, these measurements yielded fractal dimension, average diameter of primary spherules, and number of spherules, void fraction, and dynamic shape factors as function of particle size. Overall, the particulate matter properties were shown to vary significantly with engine operation condition. Lean stratified operation yielded the most diesel-like size distribution and the largest particulate matter number and mass concentrations, with nearly all particles being fractal agglomerates composed of elemental carbon with small amounts of ash and organics. In contrast, stoichiometric operation yielded a larger fraction of ash particles, especially at low speed and low load. Three distinct forms of ash particles were observed, with their fractions strongly dependent on engine operating conditions: sub-50 nm ash particles, abundant at low speed and low load, ash-containing fractal particles, and large compact ash particles that significantly contribute to particulate matter mass loadings.

European Regulatory Framework and Particulate Matter Emissions of Gasoline Light-Duty Vehicles: A Review

“…Engine studies have also shown high EC percentages (70-93%) [98,110], but other studies have found much lower percentages (15-35%) [111,112]. With dedicated engine studies it was also shown that idle or fuel cut conditions can increase the volatile part [110] and that the EC fraction is higher under lean stratified conditions (80%) compared to stoichiometric (60%) [113].…”

Correlation of nanoparticle size distribution features to spatiotemporal flame luminosity in gasoline direct injection engines

“…It is generally held that solid accumulation mode particles, those with mobility diameter ( D p ) approximately equal to 30–500 nm, mostly consist of carbonaceous soot. Conversely, solid nucleation mode ( D p ∼ 3–30 nm) particles do not consist of nucleated organics, but rather of ash metals originating from the engine lubricating oil 24–26 and potentially of primary soot particles. 25 As given in Figure 3(a), the PSD for stoichiometric engine conditions with the most advanced injection timing settings resulted in a large concentration in the accumulation mode size range and the latest injection led to large concentrations in the ash nucleation mode size range.…”

“…Conversely, solid nucleation mode ( D p ∼ 3–30 nm) particles do not consist of nucleated organics, but rather of ash metals originating from the engine lubricating oil 24–26 and potentially of primary soot particles. 25 As given in Figure 3(a), the PSD for stoichiometric engine conditions with the most advanced injection timing settings resulted in a large concentration in the accumulation mode size range and the latest injection led to large concentrations in the ash nucleation mode size range. Although size distribution and mass concentration between these two cases were very different, the total PN concentrations were on the same order of magnitude (10 12 ) as shown in Table 3.…”

Trends in on-road transportation, energy, and emissions

“…PM mass from a GDI engine appears to have a large BC component (Maricq, Szente, and Jahr 2012). Depending on engine operating conditions, particles may consist of various amounts of amorphous carbon, semivolatile organic compounds (SVOCs), and ash contents (Karjalainen et al 2014;Zelenyuk et al 2016). The majority of PNs are smaller than 100 nm (Amanatidis et al 2017;Chen et al 2017;Hassaneen, Samuel, and Whelan 2011;Myung, Ko, and Park 2014;Tan et al 2016;Yamada, Funato, and Sakurai 2015).…”