On-Road Measurement of Particle Emission in the Exhaust Plume of a Diesel Passenger Car (original) (raw)
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Formation potential of vehicle exhaust nucleation mode particles on-road and in the laboratory
Atmospheric Environment, 2005
A mobile laboratory equipped with gas analysers, a particle number counter and a scanning mobility particle sizer was employed to measure the exhaust particle size distributions of a diesel Euro III passenger car, chasing its exhaust plume on a high-speed track at 50, 100 and 120 km h À1 . Emissions from the same vehicle were also measured in the laboratory under the same driving conditions, using a partial flow sampling system with constant sampling conditions. The vehicle was equipped with an oxidation catalyst and was operated on diesel fuel with 280 ppm wt. sulphur content. Similar results for the exhaust aerosol behaviour were found in both sampling environments, despite the different dilution ratio, sampling temperature and residence time of the aerosol in dilute conditions. A relatively constant soot particle mode was formed in all cases and, in addition, a nucleation mode started to form at 100 km h À1 and became more stable at 120 km h À1 . No nucleation mode was observed at 50 km h À1 road load. The similar behaviour of nucleation mode particles both in the chasing and the laboratory tests indicated that such small volatile particles are a true vehicle emission component and not a dilution artefact. Additional measurements in the laboratory with varying engine load revealed that the nucleation mode formation is sensitive to exhaust gas temperature and its occurrence in increased temperature is repeatable and stable for long sampling times. The findings of this study indicate that nucleation mode particles are an actual emission component of diesel passenger cars and they need to be considered in relevant exhaust aerosol characterization studies. r
Atmospheric Environment, 2007
Vehicle particle emissions are studied extensively because of their health effects, contribution to ambient PM levels and possible impact on climate. The aim of this work was to obtain a better understanding of secondary particle formation and growth in a diluting vehicle exhaust plume using 3-d information of simulations together with measurements. Detailed coupled computational fluid dynamics (CFD) and aerosol dynamics simulations have been conducted for H 2 SO 4 -H 2 O and soot particles based on measurements within a vehicle exhaust plume under real conditions on public roads. Turbulent diffusion of soot and nucleation particles is responsible for the measured decrease of number concentrations within the diesel car exhaust plume and decreases coagulation rates. Particle size distribution measurements at 0.45 and 0.9 m distance to the tailpipe indicate a consistent soot mode (particle diameter D p $50 nm) at variable operating conditions. Soot mode number concentrations reached up to 10 13 m À3 depending on operating conditions and mixing.
Atmospheric Environment, 2009
Please cite this article as: Wehner, B., Uhrner, U., von Löwis, S., Zallinger, M., Wiedensohler, A. Aerosol number size distributions within the exhaust plume of a diesel and a gasoline passenger car under on-road conditions and determination of emission factors, Atmospheric Environment (2008), Abstract 13 14 A new setup has been developed and built to measure number size distributions of exhaust 15 particles and thermodynamic parameters under real traffic conditions. Measurements have 16 been performed using a diesel and a gasoline passenger car driving with different speeds and 17 engine conditions. Significant number of nucleation mode particles was found only during 18 high load conditions, i.e. high car and engine speed behind the diesel car. The number 19 concentration of soot mode particles varied within a factor of two for different engine 20 conditions while the concentration of nucleation mode particles varied up to two orders of 21 magnitude. The results show that roadside measurements are still quite different from those 22 behind the tailpipe. Beside dilution also transformation processes within the first meter behind 23 the tailpipe play an important role, such as nucleation and growth. Emission factors were 24 calculated and compared with those obtained by other studies. Emission factors for particles 25 larger than 25 nm (primary emissions) varied within 1.1·10 14 km -1 and 2.7 ·10 14 km -1 for the 26 diesel car and between 0.6·10 12 km -1 and 3.5 ·10 12 km -1 for the gasoline car. The advantage of 27 these measurements is the exhaust dilution under atmospheric conditions and the size-28 resolved measurement technique to divide into primary emitted and secondary produced 29 particles. 30 31 ARTICLE IN PRESS
Volatile Nanoparticle Formation and Growth within a Diluting Diesel Car Exhaust
Journal of the Air & Waste Management Association, 2011
A major source of particle number emissions is road traffic. However, scientific knowledge concerning secondary particle formation and growth of ultrafine particles within vehicle exhaust plumes is still very limited. Volatile nanoparticle formation and subsequent growth conditions were analyzed here to gain a better understanding of "real-world" dilution conditions. Coupled computational fluid dynamics and aerosol microphysics models together with measured size distributions within the exhaust plume of a diesel car were used. The impact of soot particles on nucleation, acting as a condensational sink, and the possible role of low-volatile organic components in growth were assessed. A prescribed reduction of soot particle emissions by 2 orders of magnitude (to capture the effect of a diesel particle filter) resulted in concentrations of nucleation-mode particles within the exhaust plume that were approximately 1 order of magnitude larger. Simulations for simplified sulfuric acid-water vapor gas-oil containing nucleation-mode particles show that the largest particle growth is located in a recirculation zone in the wake of the car. Growth of particles within the vehicle exhaust plume up to detectable size depends crucially on the relationship between the mass rate of gaseous precursor emissions and rapid dilution. Chassis dynamometer measurements indicate that emissions of possible hydrocarbon precursors are significantly enhanced under high engine load conditions and high engine speed. On the basis of results obtained for a diesel passenger car, the contributions from light diesel vehicles to the observed abundance of measured nucleation-mode particles near busy roads might be attributable to the impact of two different time scales: (1) a short one within the plume, marked by sufficient precursor emissions and rapid dilution; and (2) a second and comparatively long time scale resulting from the mix of different precursor sources and the impact of atmospheric chemistry. IMPLICATIONS Volatile nucleation-mode particles still dominate curbside size distributions. In contrast to nonvolatile vehicle particle number emission factors, the formation of volatile curbside particle number concentrations depends on processes that cannot be reproduced on vehicle test benches in a reasonably economic way. Greater understanding of formation processes and subsequent growth, chemical composition, and the impact of volatile precursor mix is needed to properly evaluate health effects. An integrated approach is necessary when assessing emissions from different sources and measures.
Modeling of Particle Size Distribution at the Exhaust of Internal Combustion Engines
SpringerBriefs in Applied Sciences and Technology, 2017
Nowadays, the interest in the effect of exhaust emissions from road vehicles on public health is stronger than ever. Great attention is paid to particulate matter (PM) both for its impact on the environment and for the adverse effect on human health. The internal combustion engines (ICEs), both spark ignition (SI), and compression ignition (CI) are the main sources of PM emissions in the urban area. Particles are usually classified according to their diameter in coarse particles, diameter larger than 10 lm (PM10) and fine particles, diameter smaller than 2.5 lm (PM2.5). Further distinction is made for PM2.5, particles smaller than 100 nm are called ultrafine particles and those smaller than 50 nm are called nanoparticles. The chemical nature of the particles as well as the number and size depends on the engine type. Diesel engine particles consist mainly of agglomerated carbonaceous primary particles on which volatile organic material is adsorbed. The gasoline particles, instead, are mainly composed of organic fraction. Both CI and SI engines emit mainly particles in the ultrafine size range. Anyway, the particles' emissions from gasoline direct injection (GDI) engines are higher than that for port fuel injection (PFI) engines and Diesel engines equipped with a Diesel particulate filter (DPF). The severe adverse effects on human health of fine and ultrafine particles emitted from internal combustion were well described in the literature [1-3]. Recent studies evidenced the strict relation between the particle size and the impact on heart and brain [4]. Smaller particles can, in fact, penetrate more easily the cell membranes than large particles [5]. Considering the negligible weight of the fine particle, a particle number (PN) emission limit is enforced in addition to the PM mass emission limits for particles larger than 23 nm at the Euro 6 (2014) for all categories of light-duty (LD) DI vehicles. Great efforts are paid to reduce the particle emissions. Several solutions are under study, regarding the optimization of the combustion and the use of biofuel to reduce particle formation as well as the improvement of after-treatment devices for the reduction of emissions at the exhaust. In any case, availability of real-time information on the characteristics of particulate emissions, such as particle number and size, would enable the development of advanced closed-loop control
Composition of Semi-volatile Particles from Diesel Exhaust
SAE Technical Paper Series, 2005
Vehicle exhaust particles from diesel passenger vehicles were studied in terms of volatility and chemical composition. Condensation of semi-volatile compounds leads to particle growth during exhaust dilution and cooling. The particle growth was observed to be particle surface related. At higher vehicle speed and load some of the semi-volatile material forms nucleation particles that are dominating the particle number concentration. The nucleation mode is completely volatile at 180°C and consists mainly of sulfate. The amount of organic material is smaller. The organics/sulfate ratio is larger for the soot mode indicating an earlier condensation process of organics before they are incorporated in the nucleation process. Under typical atmospheric dilution conditions most of the semi-volatile material is present in the soot mode. The semi-volatile material evaporates at temperature between 130°C and 180°C. Thermal treatment using a thermodenuder enables complete evaporation of the nucleation particles, however not all material from the soot particles is removed.
Environmental Science & Technology, 2005
Mass spectrometric measurements of size and composition of diesel exhaust particles have been performed under various conditions: chassis dynamometer tests, field measurements near a German motorway, and individual car chasing. Nucleation particles consisting of volatile sulfate and organic material could be detected both at the chassis dynamometer test facility and during individual car chasing. We found evidence that if nucleation occurs, sulfuric acid/water is the nucleating agent. Low-volatile organics species condense only on the preexisting sulfuric acid/water clusters. Nucleation was found to depend strongly on various parameters such as exhaust dilution conditions, fuel sulfur content, and engine load. The latter determines the fraction of the fuel sulfur that is converted to sulfuric acid. The organic compounds (volatile and lowvolatile) condense only on preexisting particles, such as both sulfuric acid nucleation particles and larger accumulation mode soot particles. On the latter, sulfuric acid also condenses, if the conditions for nucleation are not given. The overall ratio of sulfate to organic (volatile and lowvolatile) is also strongly dependent on the engine load. It was found that the production of nucleation particles even at high engine load can be suppressed by using lowsulfur fuel.
Sulfur Driven Nucleation Mode Formation in Diesel Exhaust under Transient Driving Conditions
Environmental Science & Technology, 2014
Sulfur driven diesel exhaust nucleation particle formation processes were studied in an aerosol 16 laboratory, on engine dynamometers, and on the road. All test engines were equipped with a 17 combination of a diesel oxidation catalyst (DOC) and a partial diesel particulate filter (pDPF). At steady 18 operating conditions the formation of semi-volatile nucleation particles directly depended on SO 2 19 conversion in the catalyst. The nucleation particle emission was most significant after a rapid increase in 20 engine load and exhaust gas temperature. Results indicate that the nucleation particle formation at 21 transient driving conditions does not require compounds such as hydrocarbons or sulfated hydrocarbons, 22 but on the other hand, it cannot be explained only by the nucleation of sulfuric acid. A real-world 23 exhaust study with a heavy duty diesel truck showed that the nucleation particle formation occurs even 24 with ultra-low sulfur diesel fuel, even at downhill driving conditions, and that nucleation particles can 25 contribute 60% of total particle number emissions. In general, due to sulfur storage and release within 26 the exhaust aftertreatment systems and transients in driving, emissions of nucleation particles can even 27 be the dominant part of modern diesel vehicle exhaust particulate number emissions. 28
Detailed Characterization of Solid and Volatile Particle Emissions of Two Euro 6 Diesel Vehicles
Applied Sciences
The solid particle number emissions of Diesel vehicles are very low due to the particulate filters as exhaust aftertreatment devices. However, periodically, the trapped particles are oxidized (i.e., active regeneration) in order to keep the backpressure at low levels. The solid particle number emissions during regenerations are only partly covered by the regulations. Many studies have examined the emissions during regenerations, but their contribution to the overall emissions has not been addressed adequately. Furthermore, the number concentration of volatile particles, which is not included in the regulations, can be many of orders of magnitude higher. In this study, the particulate emissions of two light-duty Euro 6 vehicles were measured simultaneously at the tailpipe and the dilution tunnel. The results showed that the weighted (i.e., considering the emissions during regeneration) solid particle number emissions remained well below the applicable limit of 6 × 1011 #/km (solid pa...
2013
Particle emissions have been generally associated to diesel engines. However, spark-ignition direct injection (SI-DI) engines have been observed to produce notable amounts of particulate matter as well. The upcoming Euro 6 legislation for passenger cars (effective in 2014, stricter limit in 2017) will further limit the particulate emissions from SI engines by introducing a particle number emission (PN) limit, and it is not probable that the SI-DI engines are able to meet this limit without resorting to additional aftertreatment systems. In this study, the solid particle emissions of a SI-DI passenger car with and without an installed Particle Oxidation Catalyst (POC ®) were studied over the New European Driving Cycle (NEDC) on a chassis dynamometer and over real transient acceleration situations on road. It was observed that a considerable portion of particle number emissions occurred during the transient acceleration phases of the cycle. The application of the POC resulted in a reduction of those emission peaks and, as a conclusion, the car was able to meet the 2017 Euro 6 particle number emission limit with the POC. The on-road measurement confirms the results obtained on the chassis dynamometer in that the majority of particle number emissions associated with SI-DI engines arise from transient acceleration situations. The POC efficiency was verified also on road by significantly reducing the particle number emission peaks caused during accelerations.