Reduction Of Particulate Emissions Research Articles

The effect of varying EGR and intake air boost on hydrogen-diesel co-combustion in CI engines

This paper presents a H2-diesel fuel co-combustion study undertaken on a supercharged, direct injection, diesel engine investigating the combustion characteristics and emissions production at a range of engine loads (IMEP), EGR levels and intake air boosting conditions. The utilisation of EGR and intake air boost with H2-diesel fuel co-combustion allows simultaneous NOx and particulate emissions reduction at conditions closer to on-road driving conditions.The results showed that while H2 can be favourable in reducing CO2 and particulate emissions, it causes an increase in NOx emissions when the intake energy contribution from H2 is increased. A reduction in the number of fine and ultrafine particles (diameter 0.05–0.2 μm) was observed when H2 was added to the engine, especially at the low and intermediate intake air boost levels. At high EGR levels (equivalent to 2% intake O2 concentration reduction) significant reductions in exhaust particulate mass of up to 75% were observed at 15% energy from H2. An attempt was made to identify the optimum H2 operating window at the different engine loads, intake air boost and EGR levels.

Effects of aromatics, olefins and distillation temperatures (T50 & T90) on particle mass and number emissions from gasoline direct injection (GDI) vehicles

Abstratct Fuel quality is among the primary reasons for severe vehicle pollution. A limited understanding of the effects of gasoline properties on modern vehicle emissions is one obstacle for the establishment of stricter fuel standards in China. The goal of this study was to evaluate the effects of aromatic and olefin contents and T50 and T90 (defined as the 50%v and 90%v distillation temperatures) on tailpipe emissions from gasoline direct injection (GDI) vehicles compliant with China 4 standards. Both gaseous and particle emissions using different types of gasoline were measured. Changing aromatic and olefin contents had relatively small impacts on fuel consumption. Compared with olefins and T90, the regulated gaseous emissions were impacted more by aromatics and T50. Evident decreases of the particle mass (PM) and particle number (PN) emissions were noticed when the aromatic content and T90 decreased. Reducing the olefin content slightly decreased the PM emissions and increased the PN emissions. With decreasing T50, the PM emissions increased and the PN emissions slightly decreased. These results suggest that aromatic content and T90 should be decreased to reduce particle emissions from GDI vehicles. The information presented in this study provides some suggestions for how to improve gasoline quality in China.

Air staging strategies in biomass combustion-gaseous and particulate emission reduction potentials

Gaseous and particulate emissions have been investigated with different air staging strategies over a wide range of secondary air flow rates. Laboratory scale wood pellet combustor, supplied by an underfeed fuel bed input, is used. The air staging strategies have been employed to study burning rate, temperature in primary and post combustion zones, and NO, CO and PM emissions, taking into account the air to fuel stoichiometric ratio. 50% CO reduction and 9 times less particle mass concentration than non-staged combustion are achieved by deploying a uniform secondary air module in a higher position from the bed. The minimum NO (37% reduction than non-staged) measured in the non-uniform air distribution module at the higher flow rate with lower distance from the fuel bed. The results demonstrate a trade-off between NO and CO, PM emissions but also significant potential for reducing particulate and gaseous emissions by deploying air staging in the pellet combustor.

Influence of a Direct Firebed Cooling in a Residential Wood Pellet Boiler with an Ash-Rich Fuel on the Combustion Process and Emissions

The crucial point in inorganic particle formation from biomass combustion is the temperature-dependent release of inorganic compounds, especially potassium (K). Currently common wood fuels comprise a comparatively low amount of K, but the increased usage of wood energy requires new feedstocks in the future. Potentially new feedstocks like short-rotation-coppice (SRC), fuels from agriculture (e.g. straw) or wood from broad-leafed trees of low rotation contain usually high ash contents and/or high potassium concentrations. Apparently, these feedstocks will cause increased inorganic particle emissions from biomass combustion processes. The principle of a decreased firebed temperature as primary measure aiming at a retention of K in the ashes of the firebed is a common approach for particle emission reduction and was investigated in several previous studies. The present study describes the usage of an ash-rich fuel from SRC-pellets made from willow in a residential pellet boiler modified with an unique protot...

An investigation on particle emission from a new laser printer using an environmental chamber

In this study, emissions of ultrafine particles from a new laser printer were evaluated as a function of toner coverage, number of pages printed, fuser temperature and cartridge rotation during different printing orders. Eight combinations of printing jobs were specifically designed to represent eight printing orders. The toner coverage was found to be an important factor affecting particle emissions from the printer. The printing job without toner coverage (0%) acted as a cleaning process, which would tentatively reduce particle emissions in the next job. Particles generated in printing job with toner coverage (5%) could superimpose onto those emitted from the next job, leading to higher particle number emission in the next job than the previous one. Apart from toner coverage, cartridge rotation was an important factor enhancing particle emissions. Cartridge in rotation mode with/without toner coverage could both cause particle emissions and high fuser temperature. The relationship between the particle emission and the temperature of the fuser unit was very strong ( r2 = 0.96). The regression relationship satisfied a positive power law-rise equation. We also found that ventilation for a long period, printing with no cartridge rotation, and/or printing blank pages before toner page printing could reduce particle emissions.

Evolution and current understanding of physicochemical characterization of particulate matter from reactivity controlled compression ignition combustion on a multicylinder light-duty engine

Low-temperature compression ignition combustion can result in nearly smokeless combustion, as indicated by a smoke meter or other forms of soot measurement that rely on absorbance due to elemental carbon content. Highly premixed low-temperature combustion modes do not form particulate matter in the traditional pathways seen with conventional diesel combustion. Previous research into reactivity controlled compression ignition particulate matter has shown, despite a near zero smoke number, significant mass can be collected on filter media used for particulate matter certification measurement. In addition, particulate matter size distributions reveal that a fraction of the particles survive heated double-dilution conditions. This study summarizes research completed at Oak Ridge National Laboratory to date on characterizing the nature, chemistry and aftertreatment considerations of reactivity controlled compression ignition particulate matter and presents new research highlighting the importance of injection strategy and fuel composition on reactivity controlled compression ignition particulate matter formation. Particle size measurements and the transmission electron microscopy results do show the presence of soot particles; however, the elemental carbon fraction was, in many cases, within the uncertainty of the thermal–optical measurement. Particulate matter emitted during reactivity controlled compression ignition operation was also collected with a novel sampling technique and analyzed by thermal desorption or pyrolysis gas chromatography mass spectroscopy. Particulate matter speciation results indicated that the high boiling range of diesel hydrocarbons was likely responsible for the particulate matter mass captured on the filter media. To investigate potential fuel chemistry effects, either ethanol or biodiesel were incorporated to assess whether oxygenated fuels may enhance particle emission reduction.

Diesel oil with bioethanol as a fuel for compression-ignition engines

The research focussed on working out the stable, homogenous ethanol-diesel oil fuel containing co-solvent, with properties close to these required for commercial diesel oil. The influence of bioethanol content on properties of bioethanol-diesel oil blends was examined. Two different diesel oils were tested: diesel oil containing 7% V/V of fatty acids methyl esters and diesel oil without esters. Bioethanol content ranged from 5% V/V to 30% V/V. Because of the poor miscibility, the action of different alcoholic co-solvents at 5% and 10% volume concentrations was estimated. The physical stability of blends was tested visually and with the use of multiple light scattering technique. Admixture of bioethanol deteriorated physicochemical and functional properties of the fuels, therefore some additives improving these properties were investigated. On the base of the research results two formulas of fuels containing diesel oil (without and with 7% V/V of fatty acids methyl esters), 15% V/V bioethanol, 5% V/V co-solvent (2-ethyl-1-hexanol) and appropriate additives were prepared and tested on chassis dynamometer with Ford Escort 1.8 TD. The effect of tested fuels on engine performance and emissions was determined. Experimental results showed the engine power and torque loss over 10% in case of diesel-bioethanol-co-solvent mixture. Presence of fatty acids methyl esters caused further deterioration of these parameters and had a negative influence on engine running. Moreover, esters contributed to an increase in hydrocarbons, carbon monoxide emissions in comparison with diesel oil. The only advantage of this fuel was reduction of particulate matters emission. The fuel without fatty acids methyl esters also reduced emission of particulate matters while emissions of other tested harmful substances were at the same level as for diesel oil.

Influence of firebed temperature on inorganic particle emissions in a residential wood pellet boiler

The temperature-dependent release of inorganic elements is the first step of the main formation pathway of particle emissions in automatically fired biomass burners. To investigate this step, a residential pellet boiler with an underfeed-burner was equipped with a direct firebed cooling. This test setup enabled decreased firebed temperatures without affecting further parameters like air flow rates or oxygen content in the firebed. A reduction of particle emissions in PM1-fraction at activated firebed cooling was found by impactor measurement and by optical particle counter. The affected particles were found in the size range <0.3 μm and have been composed mainly of potassium chloride (KCl). The chemical analysis of PM1 and boiler ash showed no statistically significant differences due to the firebed cooling. Therefore, our results indicate that the direct firebed cooling influenced the release of potassium (K) without affecting other chemical reactions.

Chemical composition and source identification of rainwater constituents at an urban site in Xi’an

Major ions, pH and electric conductivity (EC) in rainwater samples collected from June 2011 to July 2012 were analyzed to evaluate chemical characteristics and source apportionment of rainwater in Xi’an, a city located on the loess deposits. The rainwater was slightly alkaline with a daily volume-weighted mean (VWM) pH of 7.7, which ranged from 7.4 to 8.4. The VWM concentrations of major ions followed the order of Ca2+ > SO42− > NH4+ > NO3− > Cl− > Na+ > K+ > Mg2+ > F−. Ca2+ and SO42− dominated in cations and anions, respectively. Investigations of neutralization factors indicated that the acidity of rainwater in Xi’an was neutralized by NH4+ and Ca2+, which presented relatively higher neutralization capability than cities in southern China. The back trajectory analysis showed that the chemistry of rainwater in Xi’an is influenced by local pollutions sources and soil dust in local and remote area. Large inputs of soil dust and coal combustion during the winter and spring led to higher values of major ions and pH values during dry seasons than wet seasons. The principal factor analysis, correlation analysis, and source apportionment indicated that SO42− and NO3− were from anthropogenic sources, while Ca2+, K+, and Mg2+ were from crust fractions. The estimated annual wet depositions for sulfur, nitrogen, and calcium were 3.9, 1.5, and 4.2 t/km2, respectively. Although rainwater acidity in Xi’an was mainly caused by H2SO4, the contribution of HNO3 will be enhanced due to increasing NOx and relatively stable SO2 emissions in the future. The high concentrations of EC, SO42−, and NO3− in rainwater indicated Xi’an is severely polluted. To improve air quality in Xi’an, simultaneous reduction of particle emissions and fossil fuel and vehicles emissions are worthy of advocating. The results have implications for identification of potential sources in rainwater and for evaluation of air quality improvement in Xi’an and other similar cities in China.

Tailor-Made Fuels from Biomass: Potentials of 2-butanone and 2-methylfuran in direct injection spark ignition engines

Two possible future biofuels, 2-butanone also referred to as methyl ethyl ketone (MEK) and 2-methylfuran, identified within the Cluster of Excellence “Tailor-Made Fuels from Biomass” (TMFB), have been evaluated as pure fuels in the present study. Investigations of the autoignition tendency were carried out on a rapid compression machine (RCM), whereas thermodynamic investigations were conducted on a direct injection spark ignition single cylinder research engine. 2-Methylfuran and 2-butanone were compared against the present benchmark biofuel for spark ignition engines ethanol and conventional RON95 gasoline. A similar autoignition tendency compared to ethanol was found for 2-methylfuran. In case of 2-butanone very high ignition delay times were measured, even higher than for ethanol and 2-methylfuran. For 2-butanone and 2-methylfuran, the lower heat of vaporization in combination with higher vapor pressure and better primary breakup compared to ethanol are beneficial for mixture formation. During the engine testing for both fuels, superior characteristics compared to conventional gasoline and ethanol were identified. In case of 2-methylfuran, an increased combustion stability, especially at low engine load and cold boundary conditions, could be found at a higher knock resistance than conventional gasoline. In combination with increased compression ratio this enables an efficiency increase of up to 19%, whereas for ethanol an even further increase of up to 21% is possible. 2-Butanone shows increased combustion stability at low engine load and cold boundary conditions compared to ethanol and also conventional gasoline as well as highest knock resistance equal to ethanol. However, for both 2-butanone and 2-methylfuran increased emissions of nitrogen oxides were found when compared to ethanol. For both possible future biofuels and also ethanol, a significant reduction of particle emissions compared to conventional gasoline was found.

Hexane decomposition without particle emission using a novel dielectric barrier discharge reactor filled with porous dielectric balls

This study investigated the decomposition of n-hexane in 15% O2 (N2 balance) in dielectric barrier discharge (DBD) reactors filled with three different kinds of dielectric balls, viz. quartz, less porous, and porous alumina balls. Products of n-hexane decomposition were analyzed by using a gas chromatograph (GC), gas chromatography–mass spectrometry (GC–MS), Fourier-transform infrared (FTIR) spectroscopy, and scanning mobility particle sizer (SMPS). The main products of n-hexane decomposition are CO, CO2, and liquid particles. The DBD reactor filled with porous alumina balls can completely adsorb the liquid particles and reduce particle emission. GC–MS and FTIR analysis results show that the liquid particles mainly compose 3-hexanone and 2-hexanone.

Reduction in Particle Emissions with Gasoline Engines with Direct Injection

Reduction in Particle Emissions with Gasoline Engines with Direct Injection

A study on the combustion and emission characteristics of an SI engine under full load conditions with ethanol port injection and gasoline direct injection

Abstract Ethanol has the potential to improve engine efficiency and reduce harmful emissions when used as fuel in a spark-ignited engine. Ethanol is mostly supplied in a splash-blended form with gasoline or in a pure form; however, this is not an optimal way of using ethanol because the use of ethanol leads to increased brake specific fuel consumption. To fully utilize the merits of ethanol, on-demand control of ethanol and gasoline is required so that the fuel-blending ratio can be altered according to the engine operating conditions. This study investigated the effect of ethanol port fuel injection and gasoline direct injection systems on engine combustion and emission characteristics under full load conditions. The experiment was conducted using two different compression ratios and various ethanol injection timings. Knock occurrence decreased as the ethanol injection timing was held while intake valves were open. Minor reductions in carbon monoxide, total hydrocarbon, and particulate emissions were observed under a compression ratio of 9.5, while the reduction in emissions became significant under a compression ratio of 13.3 as the amount of ethanol injection increased.

Source Identification of Volatile Organic Compounds and Particulate Matters in an Urban and Industrial Areas of Turkey

Elevated levels of volatile organic compounds (VOCs) and particulate matters have been observed in recent years in Kocaeli, Turkey, despite improvements in pollution prevention technology that have led to a reduction in gas and particulate emissions. Local authorities should devise alternative strategies to reduce the possible health effects of a variety of pollutants that affect air quality. The objective of this study was to identify potential sources of VOCs, fine particulate matter (PM2.5) and coarse particulate matter (PM10) concentrations in atmospheric aerosols that were collected in the highly industrialised area of Kocaeli, Turkey, during the winter and summer months by using wind directions. Samples were collected from May 2006 to January 2007, and concentrations of eight elements (As, Cr, Cu, Mn, Ni, Pb, V and Zn) were measured using energy dispersive X-ray fluorescence (EDXRF) and wavelength dispersive X-ray fluorescence (WDXRF) spectrometer. Samples were analysed for thirteen VOCs, including benzene, toluene, m/p-xylene, o-xylene, ethylbenzene, styrene, cyclohexane, 1,2,3-trimethylbenzene, 1,2,4trimethylbenzene, hexane, nonane and dodecane using thermal desorption (TD) and a gas chromatography/flame ionisation detector (GC/FID). The results show that vehicular emissions, oil and coal combustions, petroleum refinery and hazardous and medical waste incinerator are the significant sources of VOCs, PM 2.5 and PM 10 concentrations in Kocaeli.

Performance of optimised SCR retrofit buses under urban driving and controlled conditions

This work presents the first comprehensive real-world emissions results from urban buses retrofitted with an optimised low-NO2 selective catalytic reduction (SCR) system. The SCRT system combines a CRT (Continuously Regenerating Trap) to reduce particle emissions and SCR to reduce NOx emissions. The optimised low-NO2 SCRT was designed to work under urban conditions where the vehicle exhaust gas temperature is often too low for many SCR systems to work efficiently. The system was extensively tested through on-road and test track measurements using a vehicle emission remote sensing instrument capable of measuring both nitric oxide (NO) and nitrogen dioxide (NO2). Over 700 on-road measurements of the SCRT system were made in London. Compared with identical buses operating under the same conditions fitted with a CRT, NO2 emissions were reduced by 61% and total NOx by 45%. Under test track conditions reductions in NOx of 77% were observed. The test track results do reveal however that compared with an original Euro III bus without a CRT, the SCRT retrofit bus emissions of NO2 are 50% higher. Engine-out and tailpipe measurements of several important engine parameters under test track conditions showed the important effect of SCR inlet temperature on NOx conversion efficiency. Overall, we conclude that retrofitting urban buses to use low-NO2 SCRT systems is an effective method for delivering NOx and NO2 emissions reduction.

Radiation contributed more than temperature to increased decadal autumn and annual carbon uptake of two eastern North America mature forests

The eastern North America mature deciduous forests are increasing their carbon (C) sink, which is believed to be due to a longer growing season. In this study, we investigated the impacts of land surface phenology (LSP) and carbon uptake phenology (CUP) on the net ecosystem productivity (NEP) of the two longest-running flux tower sites in the region. Our results show that there is no trend in the start (SOS), end (EOS), and length of growing season (LOS) at both sites; nor do they explain the interannual and long-term trend in NEP. We found no evidence for a changing growing season and cannot attribute the increasing C sink to growing season length. However, there is strong trend in end (ECU) and length of net positive carbon uptake (LCU) period. ECU is delaying and LCU is getting longer, and they both explain the interannual and long-term trends in NEP. There is increasing trend of photosynthetically active radiation (PAR) at both sites in line with increasing NEP. PAR is contributing the most both to NEP and ECU. CUP is affected more by the increased photosynthetic activity partially due to increased PAR, but not by timing of spring onset and autumn senescence of leaves. There is also significant (p<0.01) reductions in emissions of sulfur oxides (SOx), nitrogen oxides (NOx), total nitrate (HNO3+NO3) and ozone since 1992. The reductions in gaseous and particulate emissions imply the occurrence of direct aerosol mediated brightening and therefore increased PAR and enhanced C uptake by eastern North America mature forests.

Evaluation of a Heat Exchanger Designed for Efficient Fine Particle Precipitation in Small-Scale Wood Combustion

There is a need to develop feasible PM reduction methods for small-scale biomass combustion installations due to their high PM emissions. In this work, we evaluated the potential of a novel prototype small-scale heat exchanger (PHX) designed for high particle emission reduction. In addition, the role of the different deposition mechanisms in such an application was studied. The PHX was connected to a wood-fired unit, and both particle and gas emissions and thermal efficiencies were evaluated. In addition, a scrubbing system, for keeping the PHX walls clean, was connected to the system. The thermal efficiency reached over 100% due to the recovered heat by water condensation, when operating the PHX at temperatures typical for floor heating. The usage of the scrubber for cleaning the PHX increased the PM1 emissions, compared to the heat exchanger (HX) reference case, but prevented fouling of the PHX tubes. The PHX was found to have fine particle precipitation efficiencies of 45% and 48%, depending on applied...

Analysis of fluid-dynamic guidelines in diesel particulate filter sizing for fuel consumption reduction in post-turbo and pre-turbo placement

Wall-flow particulate filters are in the present days a standard aftertreatment system widely used in diesel engines to reduce particle emissions and meet emission regulations. This paper deals with the analysis of the macro- and meso-geometry definition of the DPF monoliths from a fluid-dynamic modelling approach. Focus is driven to the analysis of the influence on pressure drop and hence on engine fuel economy.The influence of the DPF volume on the engine performance is analysed with a gas dynamic software including both post-turbo and pre-turbo placement under clean and soot loading conditions. A swept in cell density is also considered for different thermal integrity factors. This approach allows analysing the trends in pressure drop and cell unit geometric parameters defining the monolith thermal and mechanical performance. A discussion considering constant specific filtration area and constant filtration area is performed providing a comprehensive understanding of the DPF and engine response as volume and cellular geometry are changed. Results are leading to rigorously justify known but usually empirical guidelines for DPF design in post-turbo applications. A discussion on the potential for monolith volume reduction in pre-turbo applications with respect to the post-turbo baseline is addressed. This is based on the very low sensitivity of fuel consumption and pressure drop both to volume reduction and soot and ash loading with pre-turbo DPF configuration.

Reductions in aircraft particulate emissions due to the use of Fischer–Tropsch fuels

Abstract. The use of alternative fuels for aviation is likely to increase due to concerns over fuel security, price stability, and the sustainability of fuel sources. Concurrent reductions in particulate emissions from these alternative fuels are expected because of changes in fuel composition including reduced sulfur and aromatic content. The NASA Alternative Aviation Fuel Experiment (AAFEX) was conducted in January–February 2009 to investigate the effects of synthetic fuels on gas-phase and particulate emissions. Standard petroleum JP-8 fuel, pure synthetic fuels produced from natural gas and coal feedstocks using the Fischer–Tropsch (FT) process, and 50% blends of both fuels were tested in the CFM-56 engines on a DC-8 aircraft. To examine plume chemistry and particle evolution with time, samples were drawn from inlet probes positioned 1, 30, and 145 m downstream of the aircraft engines. No significant alteration to engine performance was measured when burning the alternative fuels. However, leaks in the aircraft fuel system were detected when operated with the pure FT fuels as a result of the absence of aromatic compounds in the fuel. Dramatic reductions in soot emissions were measured for both the pure FT fuels (reductions in mass of 86% averaged over all powers) and blended fuels (66%) relative to the JP-8 baseline with the largest reductions at idle conditions. At 7% power, this corresponds to a reduction from 7.6 mg kg−1 for JP-8 to 1.2 mg kg−1 for the natural gas FT fuel. At full power, soot emissions were reduced from 103 to 24 mg kg−1 (JP-8 and natural gas FT, respectively). The alternative fuels also produced smaller soot (e.g., at 85% power, volume mean diameters were reduced from 78 nm for JP-8 to 51 nm for the natural gas FT fuel), which may reduce their ability to act as cloud condensation nuclei (CCN). The reductions in particulate emissions are expected for all alternative fuels with similar reductions in fuel sulfur and aromatic content regardless of the feedstock. As the plume cools downwind of the engine, nucleation-mode aerosols form. For the pure FT fuels, reductions (94% averaged over all powers) in downwind particle number emissions were similar to those measured at the exhaust plane (84%). However, the blended fuels had less of a reduction (reductions of 30–44%) than initially measured (64%). The likely explanation is that the reduced soot emissions in the blended fuel exhaust plume results in promotion of new particle formation microphysics, rather than coating on pre-existing soot particles, which is dominant in the JP-8 exhaust plume. Downwind particle volume emissions were reduced for both the pure (79 and 86% reductions) and blended FT fuels (36 and 46%) due to the large reductions in soot emissions. In addition, the alternative fuels had reduced particulate sulfate production (near zero for FT fuels) due to decreased fuel sulfur content. To study the formation of volatile aerosols (defined as any aerosol formed as the plume ages) in more detail, tests were performed at varying ambient temperatures (−4 to 20 °C). At idle, particle number and volume emissions were reduced linearly with increasing ambient temperature, with best fit slopes corresponding to −8 × 1014 particles (kg fuel)−1 °C−1 for particle number emissions and −10 mm3 (kg fuel)−1 °C−1 for particle volume emissions. The temperature dependency of aerosol formation can have large effects on local air quality surrounding airports in cold regions. Aircraft-produced aerosols in these regions will be much larger than levels expected based solely on measurements made directly at the engine exit plane. The majority (90% at idle) of the volatile aerosol mass formed as nucleation-mode aerosols, with a smaller fraction as a soot coating. Conversion efficiencies of up to 2.8% were measured for the partitioning of gas-phase precursors (unburned hydrocarbons and SO2) to form volatile aerosols. Highest conversion efficiencies were measured at 45% power.

Assessment of different technical options in reducing particle emissions from gasoline direct injection vehicles

We assessed three different technical approaches targeting the control of particle number (PN) emissions from stoichiometric direct injection gasoline vehicles. The emission performance was evaluated under both the regulated New European driving cycle and the common artemis driving cycle, conducted at both 22 and −7°C test cell temperatures. The most efficient measure was found to be the installation of a gasoline particulate filter which, with a filtration efficiency of more than 90%, effectively reduced the PN emission below the legislated diesel threshold of 6×1011#/km, under all operating conditions examined. The use of 75–85% ethanol/gasoline blends on a flexi fuel vehicle resulted in large reductions in PN emissions, which spanned from approximately 20–35% under urban driving to an excess of 95% at motorway conditions. The emission performance of a Euro 4 vehicle utilizing a twin port/direct injection system verified the PN reduction potential offered by such strategies, exhibiting emissions in the 3-7×1011#/km range over all hot-start tests. The fraction of nano-sized non-volatile particles that could not be detected with the legislated PN measurement procedure ranged between 10 and 35%, that is within the levels reported for late technology diesel vehicles (Mamakos et al., 2012b. Journal of Aerosol Science, 55:31–47). The study also provided evidence of volatile artefact interference downstream of the volatile particle remover when employing condensation particle counters with a cut-off size below the legislated 23nm.