Measurement of Automotive Nonvolatile Particle Number Emissions within the European Legislative Framework: A Review

Abstract

In 2011, the European Commission introduced a limit for nonvolatile particle number (PN) emissions >23 nm from light-duty (LD) vehicles and the stated intent is to implement similar legislation for on-road heavy-duty (HD) engines at the next legislative stage. This paper reviews the recent literature regarding the operation-dependent emission of PN from LD vehicles and HD engines, and the measurement procedure used for regulatory purposes. The repeatability of the PN method is of the order of 5% and higher scatter of the results can easily be explained by the effect of the vehicles or the aftertreatment devices on the PN emissions (e.g., the fill state of the diesel particulate filters). Reproducibility remains an issue since it may exceed 30%. These high-variability levels are mainly associated with calibration uncertainties of the PN instruments. Correlation measurements between the full-flow dilution tunnels (constant-volume samplers, CVS) and the proportional partial-flow dilution systems (PFDS) showed agreement within 15% for the PN method down to 1 × 10 11 p/kWh. At lower concentrations, the PN background of the CVS and/or the PFDS can result in larger inconsistencies. The filter-based particulate matter (PM) mass and the PN emissions correlate well down to 1-2 mg/km for LD vehicles and to 2-3 mg/kWh for HD applications. The correlation improves when only elemental carbon mass is considered: it is relatively good down to 0.1-0.3 mg/km or mg/kWh. ACRONYMS AND ABBREVIATIONS ACEA Association des Constructeurs Européens d'Auto mobiles (European Automobile Manufacturers' Association) AM Accumulation mode APC AVL particle counter

Size Resolved Particle Number Emission Factors of Motorway Traffic Differentiated between Heavy and Light Duty Vehicles

“…With the separation of the volatile particles and the chosen lower particle size detection limit of 23 nm, an important part of the aerosol, possibly relevant for adverse health effects, is neglected (Giechaskiel et al, 2012). Studies indicate that both the solid particle core and/or adsorbed chemical molecules are responsible for adverse health effects (Lovik et al, 1997;Yang et al, 1999;US EPA, 2002).…”

“…The concern about the potential size dependent effect of particles for adverse health effects stimulated research work characterizing particle number size distribution of exhaust emissions (Giechaskiel et al, 2012). Only a few studies are available calculating particle size dependent emission factors (Birmili et al, 2009, Wang et al, 2010.…”

Nanoparticle Filtration Characteristics of Advanced Metal Foam Media for a Spark Ignition Direct Injection Engine in Steady Engine Operating Conditions and Vehicle Test Modes

“…Additionally, the California Air Resource Board (CARB) is debating future PM emission regulations for the low-emission vehicle (LEV)-III standards. CARB has revealed that sub-23 nm particles comprise a substantial portion of the total PM emissions from GDI vehicles [5,9,21,29,30]. The primary reason for these controversial findings of differences between the particle measurement programme (PMP) methods and CARB relates to the sensitivity of the sampling and dilution approaches for the secondary particles formed from gaseous precursors [29][30][31][32].…”

“…Engine-out particles consist of combustion-generated solid carbon particles and some organic compounds [7][8][9]18,21]. The solid particles become coated with condensed and adsorbed organic compounds, including unburned hydrocarbons and oxygenated hydrocarbons [8,[25][26][27]29,30]. Particle size distributions are generally classified into three modes: nucleation mode (5 nm < dp < 30 nm), accumulation mode (30 nm < dp < 1000 nm) and coarse mode (1000 nm < dp).…”

“…Therefore, a cost-effective gasoline particulate filter (GPF) can be adopted for GDI vehicles to reduce the nano-PM emissions to satisfy future PN emission regulations [10,27,[29][30][31][36][37][38][39]. The physical characteristics of volume, space velocity, pressure drops, exhaust temperature for natural regeneration, and particle-filtering efficiency, including sub-23 nm particles that do not negatively affect vehicle exhaust emissions and fuel efficiency, should be considered for optimized performance [5,10,25,27,30,[36][37][38][39][40][41][42][43].…”