Total Particle Number Emissions Research Articles

A comparative study of first and second generation biodiesel blends under quaternary injection strategies for enhanced engine performance and reduced emissions

Biodiesel is a promising renewable alternative fuel, offering compatibility with conventional engines without necessitating significant engine modifications. To facilitate the practical integration of biodiesel into engine systems, this study evaluates the performance of two different biodiesel blends (fatty acid methyl ester and hydrogenated catalytic) in a turbocharged inter-cooled diesel engine. The research employs quaternary injection techniques an advanced injection technique, which involve multiple injection events per cycle to enhance engine combustion and emission characterictics of the biodiesel blend fuels and comparing their performance and emission characteristics with those of conventional diesel. Results showed that fatty acid methyl ester biodiesel effectively reduced the CO, UHC, and NOx emissions at lower blend ratios (up to 10 %), with minimal impact on the brake-specific fuel consumption. Conversely, hydrogenated catalytic biodiesel demonstrates notable advantages in reducing fuel consumption with carbon monoxide and particle emissions, particularly for higher blend ratios (20 %), leading to improved indicated thermal efficiency. Additionally, an investigation on higher biodiesel blends under varying early injection timings showed that, optimal fuel efficiency was observed at an early injection timing of −43.6 °CA, accompanied by reductions in total particle number and unburned hydrocarbon emissions albeit with elevated carbon monoxide and nitrogen oxide emissions. These findings suggest that advanced injection strategies combined with sustainable biodiesel blends can significantly improve engine performance and reduce environmental impact, supporting the transition towards cleaner and more efficient transportation fuels.

Recommendations for emission testing and control of exhaust particles from a late technology mono-fuel CNG vehicle

The current study characterizes sub-23nm volatile and non-volatile particle emissions from a late technology (Euro 6d-temp) port-fuel injection vehicle, operating with compressed natural gas (CNG) as the primary fuel and E10 gasoline, as a reserve fuel. In part of the testing, gasoline was replaced with alkylate fuel or was doped with an octane booster (MMT), to understand fuel impacts better. Alkylate use resulted to the lowest total particle number (TPN) emission levels, below that of the Euro 6 limit. Increased sensitivity to primary sampling temperature was observed for CNG due to the high H/C ratio that causes water condensation in the exhaust. A minimum sampling temperature of 70oC is recommended to avoid water particles in CNG operation. The study also assessed the potential of a particle filter (PF) in controlling total and solid CNG exhaust particles. Results indicate effective PF filtration of non-volatile and volatile particles, especially in the sub-23 nm size range. Gasoline and CNG tests with PF suggest TPN10 emissions in the order of 5 × 1011 p/km, below the Euro 6 and Euro 7 regulation limit. Adopting PF as part of the aftertreatment layout would be required for control of solid and total particle emissions from CNG vehicles.

Temperature-dependent particle number emission rates and emission characteristics during heating processes of edible oils

The goal of this research is to investigate the temperature-dependent emission rates of particle numbers and emission characteristics during oil heating. Seven regularly used edible oils were studied in a variety of tests to attain this objective. First, total particle number emission rates ranging from 10 nm to 1 μm were measured, followed by an examination within six size intervals from 0.3 μm to 10 μm. Following that, the impacts of oil volume and oil surface area on the emission rate were investigated, and multiple regression models were developed based on the results. The results showed that corn, sunflower and soybean oils had higher emission rates than other oils above 200 °C, with peak values of 8.22 × 109#/s, 8.19 × 109#/s and 8.17 × 109#/s, respectively. Additionally, peanut and rice oils were observed to emit the most particles larger than 0.3 μm, followed by medium-emission (rapeseed and olive oils) and low-emission oils (corn, sunflower and soybean oils). In most cases, oil temperature (T) has the most significant influence on the emission rate during the smoking stage, but its influence was not as pronounced in the moderate smoking stage. The models obtained are all statistically significant (P < 0.001), with R2 values greater than 0.9, and the classical assumption test concluded that regressions were in accordance with the classical assumptions regarding normality, multicollinearity, and heteroscedasticity. In general, low oil volume and large oil surface area were more recommended for cooking to mitigate UFPs emission.

Contribution of traffic-originated nanoparticle emissions to regional and local aerosol levels

Abstract. Sub-50 nm particles originating from traffic emissions pose risks to human health due to their high lung deposition efficiency and potentially harmful chemical composition. We present a modeling study using an updated European Aerosol Cloud Climate and Air Quality Interactions (EUCAARI) number emission inventory, incorporating a more realistic, empirically justified particle size distribution (PSD) for sub-50 nm particles from road traffic as compared with the previous version. We present experimental PSDs and CO2 concentrations, measured in a highly trafficked street canyon in Helsinki, Finland, as an emission factor particle size distribution (EFPSD), which was then used in updating the EUCAARI inventory. We applied the updated inventory in a simulation using the regional chemical transport model PMCAMx-UF over Europe for May 2008. This was done to test the effect of updated emissions at regional and local scales, particularly in comparison with atmospheric new particle formation (NPF). Updating the inventory increased the simulated average total particle number concentrations by only 1 %, although the total particle number emissions were increased to a 3-fold level. The concentrations increased up to 11 % when only 1.3–3 nm sized particles (nanocluster aerosol, NCA) were considered. These values indicate that the effect of updating overall is insignificant at a regional scale during this photochemically active period. During this period, the fraction of the total particle number originating from atmospheric NPF processes was 91 %; thus, these simulations give a lower limit for the contribution of traffic to the aerosol levels. Nevertheless, the situation is different when examining the effect of the update closer spatially or temporally or when focusing on the chemical composition or the origin of the particles. For example, the daily average NCA concentrations increased by a factor of several hundred or thousand in some locations on certain days. Overall, the most significant effects – reaching several orders of magnitude – from updating the inventory are observed when examining specific particle sizes (especially 7–20 nm), particle components, and specific urban areas. While the model still has a tendency to predict more sub-50 nm particles compared to the observations, the most notable underestimations in the concentrations of sub-10 nm particles are now overcome. Additionally, the simulated distributions now agree better with the data observed at locations with high traffic densities. The findings of this study highlight the need to consider emissions, PSDs, and composition of sub-50 nm particles from road traffic in studies focusing on urban air quality. Updating this emission source brings the simulated aerosol levels, particularly in urban locations, closer to observations, which highlights its importance for calculations of human exposure to nanoparticles.

Investigation of the combustion and particle emission characteristics of a GDI engine with a 50 MPa injection system

The effects of injection pressure and injection timing are investigated in a gasoline direct injection engine with a 50 MPa injection system at part-load operating condition by experimental methods. The engine was invariably operated in stoichiometric air/fuel ratio, 1500 r/min engine speed and 5–15 bar break mean effective pressure (BMEP). The characteristics of combustion, particle size distribution (PSD) and particle number (PN) concentration of the emission are analyzed. The results indicate that delaying the injection timing can suppress the knocking tendency at higher engine loads, and significantly reduce fuel consumption, but the delayed injection increases particle emission. With the fuel injection pressure increased from 35 MPa to 50 MPa, the PN of all particle size segments are significantly reduced. High injection pressure has a significant effect on reducing the accumulation particles, and the PN concentration is reduced by more than 20%. The particles with a diameter of 5–23 nm (sub-23 nm) are a problem that cannot be ignored, which accounts for more than 50% of the total PN emission. A high fuel injection pressure can effectively reduce particulate matter emissions caused by late injection, thereby achieving both fuel consumption and particle emission reduction.

The role of the driving dynamics beyond RDE limits and DPF regeneration events on pollutant emissions of a Euro 6d-temp passenger vehicle

The current study investigates gaseous and particulate emissions of a diesel passenger car (Euro 6d-temp), under specific operation events, including diesel particulate filter (DPF) active regeneration. The contribution of DPF active regeneration to sub-23nm volatile and solid particle emissions was investigated in a dedicated measurement campaign. A novel exhaust gas sampling and dilution system was employed for the determination of solid particle number (SPN) emissions down to 23 nm, 10 nm, and 2.5 nm. Total particle number (TPN) emissions, including semi-volatiles, down to 10 nm and down to 5.6 nm were also measured. A DPF active regeneration was triggered during real driving emissions (RDE) testing. DPF regeneration increased NOx and SPN down to 23 nm (SPN23) by 1.7 times and 3 orders of magnitude, respectively, compared to non-regenerating conditions. A second DPF regeneration was triggered during steady-state conditions in the laboratory. Once again, SPN23 emissions were at least 3 orders of magnitude higher compared to normal operation. Under regeneration conditions, SPN down to 2.5 nm (SPN2.5) was 2.3 times higher than SPN23, which suggests that a significant number of particles reside below the regulated limit of 23 nm during DPF regeneration. Moreover, TPN emissions were at least 7 times higher than SPN ones. Both these observations suggest that a significant number of particles during DPF regeneration evades current SPN23 regulation. Based on the DPF active regeneration findings in RDE and lab conditions, the current study introduces an enhanced particulate emission factor that includes the impact of active DPF regenerations.

Effects of Water Ratio in Hydrous Ethanol on the Combustion and Emissions of a Hydrous Ethanol/Gasoline Combined Injection Engine under Different Excess Air Ratios.

Ethanol is usually combined with gasoline to manufacture ethanol–gasoline with excellent combustion characteristics. However, extracting water from hydrous ethanol to manufacture anhydrous ethanol consumed much energy, which increases the production cost of ethanol–gasoline. Many researchers have studied the combustion and emissions of hydrous ethanol–gasoline to explore the application of hydrous ethanol–gasoline as the fuel for spark-ignition engines. Most previous studies changed the hydrous ethanol ratio with fixed purity in hydrous ethanol–gasoline to study the effects of hydrous ethanol. Different from previous studies, this paper studied the effects of water ratio (Wr) in hydrous ethanol on the combustion and emissions of a hydrous ethanol/gasoline combined injection engine under different excess air ratio (λ) values. The ratios of ethanol and gasoline keep constant, while the purity of hydrous ethanol changes during the research. The experiment adopted the combined injection mode with hydrous ethanol direct injection plus gasoline port injection; the direct injection ratio was 20%. The experiment set three λ (0.9, 1, and 1.2) and five Wrs (0, 5, 10, 15, and 20%). The test engine’s speed was 1500 rpm, and the intake manifold absolute pressure was 48 kPa. Results showed that water inhibited combustion, prolonged CA 0-10 and CA 10-90, reduced Pmax and Tmax, and delayed APmax; larger λ made the deterioration on combustion more obvious, and the smaller λ had a larger tolerance to water. Water could increase torque and improve emissions, but different parameters corresponded to different optimal Wrs. For torque, the optimal Wr was 5%. For HC emissions, the optimal Wr was 0%; for CO emissions, the optimal value was 5%; and for NOx emissions, the best value was 20%. The best Wr was 10% for particle number (PN) emissions. Under the optimal Wr condition, when λ values were 0.9, 1, and 1.2, compared with pure gasoline, the torque increased by 7.5, 5.54, and 5.31%; HC emissions decreased by 21.37, 23.43, and 26.58%; NOx emissions decreased by 4.26, 11.47, and 12.55%; CO emissions decreased by 17.51, 34.56, −50%; and the total PN emissions decreased by 87.64, 89.64, and 76.07%.

Experimental Investigation on Emissions Characteristics from Urban Bus Fueled with Diesel, Biodiesel and an Oxygenated Additive from Residual Glycerin from Biodiesel Production

The aim of the study was to assess the influence of the addition of an oxygenated additive (a mixture of mono-, di- and triacetylglycerol obtained from residual glycerin within the biodiesel production scheme) on the specific fuel consumption and exhaust emissions of a EURO 3 diesel bus during its daily route through the city. To do this, the urban bus was fuelled with five fuel blends of diesel (D), biodiesel (B), additive (A) and heptanol as co-surfactant (H). A portable emissions measurement system was used to measure the exhaust gases while an engine exhaust particle system with a dilution system, both installed on the urban bus, was used for nanoparticles measurement in actual operating conditions through the city of Seville. Results showed that B95A5 (95%v/v biodiesel, 5%v/v additive) and B90A10 were the blends that most increased NOx emissions (by 24.12% and 9.85%, respectively) compared to D100. On the other hand, B47.5D47.5A2.5H2.5 was the blend that most reduced total particle number (by 31.6%) and NOx emissions (by 12%). All in all, the oxygenated additive can be efficiently blended with biodiesel to reduce particle emissions from engines without diesel particle filter, such as those in urban buses in many European cities.

Performance and pollutant emission of the reforming-controlled compression ignition engine – Experimental study

The reforming-controlled compression ignition (RefCCI) is an innovative concept integrating the benefits of the low-temperature combustion engine and the High-Pressure Thermochemical Recuperation. This combination enables achieving high thermal efficiency in a wide operating range while mitigating pollutant emissions. This work reports for the first time on results of the RefCCI concept experimental prove and investigation. The experiment findings confirm the results of the previous numerical studies. In addition, new important knowledge was gained on engine performance and emissions dependence on the injection timing of the primary and reformate fuels, as well as on the fuel mixture reactivity. The results show the thermal efficiency improvement by 4–9% (relative) compared to the same engine operation in diesel mode. In the RefCCI mode, the CO emission is lowered with the increase of load, contrary to the trend in the diesel mode. As expected, NOx and total particle number emissions are significantly lower than with the diesel counterpart. The emission of nucleation mode particles is fairly similar to diesel, but the number of accumulation mode particles is reduced by the order of magnitude.

Generation of spikes in ultrafine particle emissions from a gasoline direct injection vehicle during on-road emission tests

This study explores the generation of ultrafine particle emissions, measured in particle number (PN), based on a portable emissions measurement system (PEMS) in the City of Toronto between October and December 2019. Two driving routes were designed to include busy arterial roads and highways. All measurements were conducted between 10 a.m. and 4 p.m. Altogether, emissions from 31 drives were collected, leading to approximately 200,000 s of data. A spike detection algorithm was employed to isolate PN spikes in time series data. A sensitivity analysis was also conducted to identify the most optimum method for spike detection. The results indicate that the average emission rate during a PN spike is approximately 8 times the emission rate along the rest of the drive. In each test trip, about 25% of the duration was attributed to spike events, contributing 75% of total PN emissions. A Pearson correlation of 0.45 was estimated between the number of PN spikes and the number of sharp accelerations (above 8.5 km/h/s). The Pearson correlation between the occurrence of high engine torque (above 65.0 Nm) and the number of PN spikes was estimated at 0.80. The number of PN spikes was highest on arterial roads where the vehicle speed was relatively low, but with high variability, and including a high number of sharp accelerations. This pattern of UFP emissions leads to high UFP concentrations along arterial roads in the inner city core.

Comparison of Particle Number Emissions from In-Flight Aircraft Fueled with Jet A1, JP-5 and an Alcohol-to-Jet Fuel Blend

The aviation sector has begun to adopt alternative fuels in an effort to reduce net greenhouse gas (GHG) emissions and reduce their impact on climate change. While many lab and flight-based studies have been completed for hydro-treated esters and fatty acids (HEFA) and Fischer–Tropsch (FT) alternative fuels, only one lab study has been conducted on alcohol-to-jet synthetic paraffinic kerosene (ATJ-SPK) fuels. Here we report results from the Civil Aviation Alternate Fuels Contrails and Emissions with high blend Biojet (CAAFCEB) project which was conducted in order to gather in-flight emissions data and compare an ethanol-based ATJ-SPK fuel blend and conventional JP-5 fuel to conventional Jet A1 fuel. A research aircraft was flown while fueled with the different fuels and in-flight cruise measurements were made by a second research aircraft gathering emissions and contrail data. In this study we report particle number emission index ratios with effective cutoff diameters of 15 and 7.7 nm for total particles and 13 nm for nonvolatile particles for GE CF700-2D2 engines at cruise. The ATJ-SPK blend was found to significantly reduce total and nonvolatile particle number emissions by up to 97% compared to Jet A1 fuel, likely due to the much lower aromatic and sulfur content and higher hydrogen content of the fuel. On the other hand, the total particle emissions for the JP-5 were found to have been 4% smaller than for Jet A1; this small difference is likely due to the similar fuel compositions.

Physical Characteristics of Particle Emissions from a Medium Speed Ship Engine Fueled with Natural Gas and Low-Sulfur Liquid Fuels.

Particle emissions from marine traffic affect significantly air quality in coastal areas and the climate. The particle emissions were studied from a 1.4 MW marine engine operating on low-sulfur fuels natural gas (NG; dual-fuel with diesel pilot), marine gas oil (MGO) and marine diesel oil (MDO). The emitted particles were characterized with respect to particle number (PN) emission factors, PN size distribution down to nanometer scale (1.2-414 nm), volatility, electric charge, morphology, and elemental composition. The size distribution of fresh exhaust particles was bimodal for all the fuels, the nucleation mode highly dominating the soot mode. Total PN emission factors were 2.7 × 1015-7.1 × 1015 #/kWh, the emission being the lowest with NG and the highest with MDO. Liquid fuel combustion generated 4-12 times higher soot mode particle emissions than the NG combustion, and the harbor-area-typical lower engine load (40%) caused higher total PN emissions than the higher load (85%). Nonvolatile particles consisted of nanosized fuel, and spherical lubricating oil core mode particles contained, e.g., calcium as well as agglomerated soot mode particles. Our results indicate the PN emissions from marine engines may remain relatively high regardless of fuel sulfur limits, mostly due to the nanosized particle emissions.

Nanocluster Aerosol Emissions of a 3D Printer.

Many studies exist that characterize the aerosol emissions from fused filament fabrication three-dimensional (3D) printers. However, nanocluster aerosol (NCA) particles, that is particles in a size range under 3 nm, are rarely studied. The purpose of this study was to characterize the NCA emissions and the contribution of NCA to the total particle number emissions from a 3D printer. We used a particle size magnifier and a scanning mobility particle sizer to measure the time evolution of particle size distribution, which was used to calculate the average NCA emission rates during a printer operation in a chamber. The NCA emission rates ranged from 1.4 × 106 to 7.3 × 109 s-1 depending on the applied combination of filament material and nozzle temperature, showing increasing emission with increasing temperature. The NCA emissions constitute from 9 to 48% of the total emissions, that is, almost half of the particle emissions may have been previously neglected. Therefore, it is essential to include the low NCA size range in, for example, future 3D-printer-testing protocols, emission measurement standards, and risk management measures.

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

The particulate matter (PM) emissions of gasoline vehicles were much lower than those of diesel vehicles until the introduction of diesel particulate filters (DPFs) in the early 2000s. At the same time, gasoline direct injection (GDI) engines started to become popular in the market due to their improved efficiency over port fuel injection (PFI) ones. However, the PM mass and number emissions of GDI vehicles were higher than their PFI counterparts and diesel ones equipped with DPFs. Stringent PM mass levels and the introduction of particle number limits for GDI vehicles in the European Union (EU) resulted in significant PM reductions. The EU requirement to fulfill the proposed limits on the road resulted to the introduction of gasoline particulate filters (GPFs) in EU GDI models. This review summarizes the evolution of PM mass emissions from gasoline vehicles placed in the market from early 1990s until 2019 in different parts of the world. The analysis then extends to total and nonvolatile particle number emissions. Care is given to reveal the impact of ambient temperature on emission levels. The discussion tries to provide scientific input to the following policy-relevant questions. Whether particle number limits should be extended to gasoline PFI vehicles, whether the lower limit of 23 nm for particle number measurements should be decreased to 10 nm, and whether low ambient temperature tests for PM should be included.

Impact of lower and higher alcohol additions to diesel on the combustion and emissions of a direct-injection diesel engine.

The present investigation evaluated the combustion, performance, and emissions of four alcohol diesel blends with the same oxygen content, i.e., 13% ethanol (E13), 20% n-butanol (NB20), 20% iso-butanol (IB20), and 25% n-pentanol (P25) by volume on a 4-cylinder direct-injection diesel engine under three different engine loads, respectively. Compared with diesel, higher peak heat release rate, longer ignition delay, and shorter combustion duration have been observed for the alcohol blends; the variations are more evident for higher alcohol blends (i.e., NB20, IB20, and P25) compared with lower alcohol blend (E13), and the most evident one is IB20. Higher premixed combustion fraction and higher displacement of the diesel fuel for the higher alcohol blends suppressing the formation of the soot precursors result in a lower peak of particle size distribution, and therefore, a lower total particle number emission than that of lower alcohol blend. For the three higher alcohol blends, IB20 presents the lowest particle number emission corresponding to its longest ignition delay and highest premixed combustion fraction which inhibits soot formation. The sequence of elemental carbon emission for the alcohol blends is (from lowest to highest): IB20 < NB20 < P25 < E13, which is in line with that of peak of particle size distribution and the total particle number emission. The organic carbon emissions with different alcohol additions show similar levels because of the factors' conflict. Compared with diesel, all blends show a slight variation or no significant change in regulated gaseous emissions (CO, HC, NOx) at different loads.

Impacts of gasoline aromatic and ethanol levels on the emissions from GDI vehicles: Part 2. Influence on particulate matter, black carbon, and nanoparticle emissions

Fuel composition plays an important role on the particulate matter (PM) emissions formation from gasoline direct injection (GDI) engines. In this study, the impacts of gasoline chemical structure and physical properties on the particulate emissions were assessed for a fleet of five Tier 3 compliant GDI vehicles. All vehicles were tested on eight fuels with varying aromatic and ethanol levels, as well as varying PM indices (PMIs) over the LA92 test cycle in at least duplicate on each of the test fuels. Our results showed strong, statistically significant fuel differences for the weighted PM mass emissions and all three phases of the LA92 cycle. The higher aromatic content fuels showed increases in PM mass and black carbon emissions that were statistically significant compared to the lower aromatic fuels. The fuels with higher PMIs showed an upward, but not statistically significant, trend for PM mass emissions with increasing ethanol content likely due to ethanol’s evaporative charge cooling effect. This observation does not hold true for the lower PMI fuels. Similar trends to the weighted PM mass emissions were also seen for the cold-start and hot-running PM mass emissions, as well as for the weighted black carbon emissions, indicating a possible ethanol reinforcing effect on PM formation for the high PMI fuels. Total and solid particle number emissions also showed increases with the higher aromatic fuels compared to the lower aromatic fuels. Similar to PM mass, both total and solid particle number emissions demonstrated an upward trend for the high PMI fuels with an increase in ethanol content. While the study is consistent with other studies showing that increasing aromatics and PMI values lead to higher PM emissions, the results also suggest that this relationship is complicated by the presence of varying levels of ethanol in high aromatic and PMI fuels, where increasing levels of ethanol in these fuels can also lead to PM increases. High molecular weight and low volatility hydrocarbon species (especially aromatics) also strongly impacted particulate emissions formation in GDI vehicles.

Investigation of diesel engine performance and exhaust emissions of microalgae fuel components in a turbocharged diesel engine

Microalgae are a promising feedstock for alternative fuel for compression ignition engines due to their positive contribution to reducing greenhouse gas emissions. Microalgae are gaining significant interest as they can produce more oil than any oilseed plants. Unlike some other plant oils, the use of microalgae as an alternative to fossil fuels, can overcome food versus fuel conflict. In the current investigation, five different chemical components of microalgae hydrothermal liquefaction (HTL) biocrude paraffin, xylene, cyclo-pentanone, dioctyl-phthalate and butanol were mixed in equal volumes. Commercial diesel fuel was used as a reference fuel. The first blend consisted of 5 vol% of each of the 5 components was mixed with 75 vol% diesel. The blend is called as B1. The second blend consisted of 10 vol% of each of the 5 components was mixed with 50 vol% of diesel. This blend is called B2. The neat diesel (100% pure diesel) is called as 100D. The engine used in this study was a six-cylinder high-pressure common rail direct injection diesel engine fitted with a turbocharger. This study deals with engine performance, combustion and exhaust emission characteristics comparing diesel, B1 and B2 blends. The experimental results indicated a general reduction in both particle mass (PM) and total particle number (PN) emissions with both blends compared to those of diesel. Increase in nitrogen oxides (NOx) emissions at all four engine loads were found with both B1 and B2 blends. It was realised that the drop or rise of emissions was mainly a function of fuel-bound oxygen.

Characteristics of particle emissions and their atmospheric dilution during co-combustion of coal and wood pellets in a large combined heat and power plant

Coal combustion is one of the most significant anthropogenic CO2 and air pollution sources globally. This paper studies the atmospheric emissions of a power plant fuelled with a mixture of industrial pellets (10.5%) and coal (89.5%). Based on the stack measurements, the solid particle number emission, which was dominated by sub-200 nm particles, was 3.4×1011 MJ-1 for the fuel mixture when electrostatic precipitator (ESP) was cleaning the flue gas. The emission factor was 50 mg MJ-1 for particulate mass and 11 740 ng MJ-1 for the black carbon with the ESP. In the normal operation situation of the power plant, i.e., including the flue-gas desulphurisation and fabric filters (FGD and FF), the particle number emission factor was 1.7×108 MJ-1, particulate mass emission factor 2 mg MJ-1 and black carbon emission factor 14 ng MJ-1. Transmission electron microscopy (TEM) analysis supported the particle number size distribution measurement in terms of particle size and the black carbon concentration. The TEM images of the particles showed variability of the particle sizes, morphologies and chemical compositions. The atmospheric measurements, conducted in the flue-gas plume, showed that the flue-gas dilutes closed to background concentrations in 200 sec. However, an increase in particle number concentration was observed when the flue gas aged. This increase in particle number concentration was interpret as formation of new particles in the atmosphere. In general, the study highlights the importance of detailed particle measurements when utilizing new fuels in existing power plants.Implications: CO2 emissions of energy production decrease when substituting coal with biofuels. The effects of fuels changes on particle emission characteristics have not been studied comprehensively. In this study conducted for a real-scale power plant, co-combustion of wood pellets and coal caused elevated black carbon emissions. However, it was beneficial from the total particle number and particulate mass emission point of view. Flue-gas cleaning can significantly decrease the pollutant concentrations but also changes the characteristics of emitted particles. Atmospheric measurements implicated that the new particle formation in the atmospheric flue-gas plume should be taken into account when evaluating all effects of fuel changes.” Are implication statements part of the manuscript?

Gasoline Particulate Filters as an Effective Tool to Reduce Particulate and Polycyclic Aromatic Hydrocarbon Emissions from Gasoline Direct Injection (GDI) Vehicles: A Case Study with Two GDI Vehicles.

We assessed the gaseous, particulate, and genotoxic pollutants from two current technology gasoline direct injection vehicles when tested in their original configuration and with a catalyzed gasoline particulate filter (GPF). Testing was conducted over the LA92 and US06 Supplemental Federal Test Procedure (US06) driving cycles on typical California E10 fuel. The use of a GPF did not show any fuel economy and carbon dioxide (CO2) emission penalties, while the emissions of total hydrocarbons (THC), carbon monoxide (CO), and nitrogen oxides (NOx) were generally reduced. Our results showed dramatic reductions in particulate matter (PM) mass, black carbon, and total and solid particle number emissions with the use of GPFs for both vehicles over the LA92 and US06 cycles. Particle size distributions were primarily bimodal in nature, with accumulation mode particles dominating the distribution profile and their concentrations being higher during the cold-start period of the cycle. Polycyclic aromatic hydrocarbons (PAHs) and nitrated PAHs were quantified in both the vapor and particle phases of the PM, with the GPF-equipped vehicles practically eliminating most of these species in the exhaust. For the stock vehicles, 2-3 ring compounds and heavier 5-6 ring compounds were observed in the PM, whereas the vapor phase was dominated mostly by 2-3 ring aromatic compounds.

Total Particle Number Emissions from Modern Diesel, Natural Gas, and Hybrid Heavy-Duty Vehicles During On-Road Operation.

Particle emissions from heavy-duty vehicles (HDVs) have significant environmental and public health impacts. This study measured total particle number emission factors (PNEFs) from six newly certified HDVs powered by diesel and compressed natural gas totaling over 6800 miles of on-road operation in California. Distance-, fuel- and work-based PNEFs were calculated for each vehicle. Distance-based PNEFs of vehicles equipped with original equipment manufacturer (OEM) diesel particulate filters (DPFs) in this study have decreased by 355-3200 times compared to a previous retrofit DPF dynamometer study. Fuel-based PNEFs were consistent with previous studies measuring plume exhaust in the ambient air. Meanwhile, on-road PNEF shows route and technology dependence. For vehicles with OEM DPFs and Selective Catalytic Reduction Systems, PNEFs under highway driving (i.e., 3.34 × 1012 to 2.29 × 1013 particles/mile) were larger than those measured on urban and drayage routes (i.e., 5.06 × 1011 to 1.31 × 1013 particles/mile). This is likely because a significant amount of nucleation mode volatile particles were formed when the DPF outlet temperature reached a critical value, usually over 310 °C, which was commonly achieved when vehicle speed sustained over 45 mph. A model year 2013 diesel HDV produced approximately 10 times higher PNEFs during DPF active regeneration events than nonactive regeneration.