Exhaust Particulate Emissions Research Articles

Effect of OEM Style and Aftermarket Performance Air Filters on Vehicle Parameters

The importance of the engine air induction system has recently increased because of governmental engine exhaust particulate and evaporative emission regulations. This has created a renewed interest in optimizing the existing parameters of the air induction mechanism like the air filter, filter box, piping etc for better performance. Air filter provided on the engine intake is subjected to increased levels of abuse due to the diverse driving conditions. The OEM air filter in modern vehicles is usually a paper type air filter. Due to the increased presence of counterfeit air filter in the market, there is a possibility that filter may be of poorer quality resulting in get premature clogging. The presence of increased number of aftermarket performance filters has prompted automotive enthusiasts to replace their OEM filters with these performance filters for better performance. This study addresses the issue of whether OEM air filter replacement with aftermarket air filter (oiled media filter from K&N) improves fuel economy. The increasing air filter pressure drop in diesel-engine-powered vehicles due to clogging was measured, with primary focus on changes in vehicle fuel economy but also including acceleration and engine temperature. The performance of both types of filters in new and clogged condition in terms of pressure drop, air discharge and filtering efficiency are also studied.

Effect of atmospheric aging on volatility and reactive oxygen species of biodiesel exhaust nano-particles

Abstract. In the prospect of limited energy resources and climate change, effects of alternative biofuels on primary emissions are being extensively studied. Our two recent studies have shown that biodiesel fuel composition has a significant impact on primary particulate matter emissions. It was also shown that particulate matter caused by biodiesels was substantially different from the emissions due to petroleum diesel. Emissions appeared to have higher oxidative potential with the increase in oxygen content and decrease of carbon chain length and unsaturation levels of fuel molecules. Overall, both studies concluded that chemical composition of biodiesel is more important than its physical properties in controlling exhaust particle emissions. This suggests that the atmospheric aging processes, including secondary organic aerosol formation, of emissions from different fuels will be different as well. In this study, measurements were conducted on a modern common-rail diesel engine. To get more information on realistic properties of tested biodiesel particulate matter once they are released into the atmosphere, particulate matter was exposed to atmospheric oxidants, ozone and ultra-violet light; and the change in their properties was monitored for different biodiesel blends. Upon the exposure to oxidative agents, the chemical composition of the exhaust changes. It triggers the cascade of photochemical reactions resulting in the partitioning of semi-volatile compounds between the gas and particulate phase. In most of the cases, aging lead to the increase in volatility and oxidative potential, and the increment of change was mainly dependent on the chemical composition of fuels as the leading cause for the amount and the type of semi-volatile compounds present in the exhaust.

Application of the PMP methodology to the measurement of sub-23 nm solid particles: Calibration procedures, experimental uncertainties, and data correction methods

This paper discusses issues which will appear if the PMP methodology is extended to the measurement of particles with sizes below 23nm. In addition, the origins of sub-23nm particles from three different types of engines are discussed. An increased uncertainty was observed for the detection efficiency measurements with a particle number counter (PNC) at particle sizes below 10nm. The particle concentration reduction factor (PCRF) of a volatile particle remover for 15nm particles was higher than those for 30, 50 and 100nm particles because of increasing particle losses. Then, exhaust particle emissions from a gasoline direct injection (DI) passenger car and trucks with and without a diesel particulate filter (DPF) were measured using the PMP methodology with a PNC whose D50 value was 2.5nm (PNC_2.5) and a normal PMP PNC (PNC_23). The fluctuations of the results for PNC_23 and PNC_2.5 were almost the same when the effect of re-nucleation of semi-volatile particles was removed. Different procedures for estimating the PCRF showed varying results, –23% to +41% in the worst case. The profiles of sub-23nm particles from diesel trucks were similar to those of particles larger than 23nm. In the case of the gasoline DI car, a peculiar emission corresponding to hydrocarbon nucleation was observed in high-speed operation. Particles emitted from the diesel engines originated from combustion processes in the case of the truck without the DPF and were strongly affected by the DPF conditions in the case of the truck with the DPF.

On-road chasing and laboratory measurements of exhaust particle emissions of diesel vehicles equipped with aftertreatment technologies (DPF, urea-SCR)

A mobile emission laboratory was applied to measure particle number size distributions of exhaust emissions for base diesel, plasma-assisted burner type-DPF, and urea-SCR equipped vehicles during on-road driving and laboratory measurements using chassis dynamometer. The measurement of total particle number concentrations revealed that the base diesel had the highest concentrations, while the DPF system effectively reduced particle numbers during all operation conditions. The particle reduction rate during idling and constant speed conditions was 60-99.9% for the DPF and 10-25% for the urea-SCR. The size distributions of particles showed that the dilution ratio significantly affected the nanoparticle formation and growth, and that laboratory measurement, in general, tended to underestimate the nucleation mode (NM) (< 50 nm) particles compared to on-road results. The NM fraction during on-road measurements was the highest at low vehicle speed (20 km/h) with values of 94% for the base diesel, 96% for the DPF, and 94% for the urea-SCR equipped vehicles, and it was the lowest at increased vehicle speed (80 km/h) with values of 59% for the base diesel, 61% for the DPF, and 65% for the urea-SCR.

The Design of Exhaust Gas Cooler for Diesel Particulate Bag Filter

Currently, the application of bag-filter technology in controlling diesel exhaust particulate emissions has been close to practical stage. As one of the key links in bag-filter technology, engine exhaust cooling can directly influence working safety of the entire exhaust particulate filter system. Thermodynamic calculations and experimental research of water-cooled chiller has provided a feasible basis for water cooler to be used in actual diesel exhaust particulate emission control system. The cooler can make engine exhaust temperature drop from 400 to 180 . Even when engine works in high-speed and high-load condition, inlet exhaust temperature of cooler can descend from 500 to 190 or so after cooling, which can still meet bag-filter system requirement of below 200 .

Gaseous and Particulate Exhaust Emissions of Hybrid and Conventional Cars over Legislative and Real Driving Cycles

Road transport exhaust emissions represent the main sources of atmospheric pollution in urban areas, due to the growing number of circulating vehicles and travelled distances. In order to reduce this pollution source, stricter emission standards are periodically set by governments through- out the world. Consequently, the concentrations of gaseous pollutants and particulate mass to be measured during type-approval tests of new vehicles are becoming progressively lower; moreover from 2011, diesel cars have to comply with particle number limit. In order to assess emission levels of different technology vehicles and investigate the use of a particulate number measurement technique at the exhaust of very low-emitting vehicles, an experimental activity was carried out on three in-use vehicles: a diesel car equipped with a particulate trap (DPF), a hybrid gasoline-elec- tric car and a bi-fuel passenger car fuelled with compressed natural gas (CNG). Cold and hot gaseous and particulate emission factors and fuel consumption were measured during the execution of real and regulatory driving cycles on a chassis dynamometer. Particulate was characterized in terms of mass only for the diesel car and of particle number for all vehicles. The emissions measured over the NEDC show that all three vehicles comply with their standard limits, except CO for CNG passenger car and NOx for diesel car. Cold start influences CO and HC emissions and fuel consumption for all the tested vehicles and in particular for the hybrid car. The real driving cycle is the most critical pattern for the emissions of almost all pollutants. During constant speed tests, the emissions of particles of hybrid car are an order of magnitude lower than those of the CNG car.

Particle emissions from biodiesels with different physical properties and chemical composition

Biodiesels produced from different feedstocks usually have wide variations in their fatty acid methyl ester (FAME) so that their physical properties and chemical composition are also different. The aim of this study is to investigate the effect of the physical properties and chemical composition of biodiesels on engine exhaust particle emissions. Alongside with neat diesel, four biodiesels with variations in carbon chain length and degree of unsaturation have been used at three blending ratios (B100, B50, B20) in a common rail engine. It is found that particle emission increased with the increase of carbon chain length. However, for similar carbon chain length, particle emissions from biodiesel having relatively high average unsaturation are found to be slightly less than that of low average unsaturation. Particle size is also found to be dependent on fuel type. The fuel or fuel mix responsible for higher particle mass (PM) and particle number (PN) emissions is also found responsible for larger particle median size. Particle emissions reduced consistently with fuel oxygen content regardless of the proportion of biodiesel in the blends, whereas it increased with fuel viscosity and surface tension only for higher diesel–biodiesel blend percentages (B100, B50). However, since fuel oxygen content increases with the decreasing carbon chain length, it is not clear which of these factors drives the lower particle emission. Overall, it is evident from the results presented here that chemical composition of biodiesel is more important than its physical properties in controlling exhaust particle emissions.

On-road chasing measurement of exhaust particle emissions from diesel, CNG, LPG, and DME-fueled vehicles using a mobile emission laboratory

We designed and applied a mobile emission laboratory for on-road measurements of exhaust particles emitted from conventional diesel, compressed natural gas (CNG), liquefied petroleum gas (LPG), and dimethyl ether (DME)-fueled vehicles. Fuel type and vehicle driving conditions significantly affected the particle size distribution and the number concentrations of the nucleation mode. For all buses, the size distributions of particles in the exhaust under idling conditions had larger mode diameters than at constant speed conditions of 50 km/h or 80 km/h. The nucleation mode (< 50 nm) fraction of diesel, CNG, LPG, and DME at a constant speed of 50 km/h was 53%, 63%, 79%, and 99%, respectively, indicating that the DME-fueled bus emitted the most nanoparticles. As the vehicle speed increased from 50 km/h to 80 km/h, the nucleation mode fraction of diesel, CNG, LPG, and DME changed to 43%, 99%, 99%, and 99%, representing a significant increase in the number concentrations of nanoparticles in the CNG and LPG-fueled vehicles. The particle size distributions in the exhaust of diesel, CNG, LPG, and DME-fueled vehicles were not affected by increase in the chasing distance.

Sulfur Driven Nucleation Mode Formation in Diesel Exhaust under Transient Driving Conditions

Sulfur driven diesel exhaust nucleation particle formation processes were studied in an aerosol laboratory, on engine dynamometers, and on the road. All test engines were equipped with a combination of a diesel oxidation catalyst (DOC) and a partial diesel particulate filter (pDPF). At steady operating conditions, the formation of semivolatile nucleation particles directly depended on SO2 conversion in the catalyst. The nucleation particle emission was most significant after a rapid increase in engine load and exhaust gas temperature. Results indicate that the nucleation particle formation at transient driving conditions does not require compounds such as hydrocarbons or sulfated hydrocarbons, however, it cannot be explained only by the nucleation of sulfuric acid. A real-world exhaust study with a heavy duty diesel truck showed that the nucleation particle formation occurs even with ultralow sulfur diesel fuel, even at downhill driving conditions, and that nucleation particles can contribute 60% of total particle number emissions. In general, due to sulfur storage and release within the exhaust aftertreatment systems and transients in driving, emissions of nucleation particles can even be the dominant part of modern diesel vehicle exhaust particulate number emissions.

Understanding Effects of Bioethanol Fuel Use on Urban Air Quality: An Integrative Approach

Resultsobtained through combining different approaches, and aiming at contributing to the understanding of effects of bioethanol fuelled vehicles on urban air quality, are evaluated. The study is based on the results obtained by measurements, modelling and cost assessment estimates in a case study in Oslo under winter conditions, when the worst air quality episodes are registered and acetaldehyde and formaldehyde have the longest lifetime. Detailed levels of formaldehyde emitted by an E95-bus under on-road driving conditions are reported for the first time, and indicate that exposure to these levels may involve a high chance of developing cancer. Emission and air dispersion modelling were applied to evaluate the potential impact on urban environment. The results show that a full implementation of bioethanol (E85-vehicles) may affect urban air quality, subsequently affecting human health. Acetaldehyde emissions were estimated to increase by 233% for a full implementation of bioethanol (E85-vehicles) compared to the baseline (petrol/diesel vehicles), whereas CO2, NOx and exhaust particle emissions from traffic were estimated to decrease by 19%, 50% and 90%, respectively. Output from measurements and the air dispersion model were the basis for an impact assessment and economic valuation of implementing bioethanol fuel in a larger scale. The acetaldehyde-related health risk associated with emissions from bioethanol fuelled vehicles was estimated as oral cavity/pharynx cancer, and the related cost was found to increase by 300% for a full implementation of bioethanol relative to the current situation. Our study only shows part of the picture, and a full evaluation bearing in mind all potential pollutants’ increases and reductions would be needed.

Source Attribution of Air Pollutant Concentrations and Trends in the Southeastern Aerosol Research and Characterization (SEARCH) Network

A new approach for determining the contributions of emission sources to trends in concentrations of particulate matter and gases is developed using the chemical mass balance (CMB) method and the U.S. EPA's National Emission Inventory (NEI). The method extends our earlier analysis by using temporally varying emission profiles and includes accounting of primary and secondary particulate organic carbon with an empirical regression calculation. The model offers a potentially important tool for verifying that annual emission reductions by major source category have yielded changes in ambient pollutant concentrations. Using long-term measurements from well-instrumented monitoring sites, observed trends in ambient pollutant concentrations at urban and rural locations can be attributed to emission changes. Trends apportionment is conducted on 2000-2011 ambient monitoring data from the SEARCH network with NEI emissions data adjusted to improve interinventory consistency. The application accounts for major source category influences in southeastern U.S. regional trends; local anomalies are noted. In the SEARCH region, open burning is important as a source of CO and carbonaceous particles. Improved agreement between predicted and measured particulate carbon is obtained by increasing mobile diesel exhaust and area-source particulate carbon emissions by 1 and 20%, respectively, compared with NEI values. The method is general and is applicable to data from any monitoring site that is instrumented for criteria air pollutants, associated gases, and particle composition.

The Effect of a Three-Way Catalytic Converter on Particulate Matter from a Gasoline Direct-Injection Engine During Cold-Start

This work investigates the effect of a three-way catalytic converter and sampling dilution ratio on nano-scale exhaust particulate matter emissions from a gasoline direct-injection engine during cold-start and warm-up transients. Experimental results are presented from a four cylinder in-line, four stroke, wall-guided direct-injection, turbo-charged and inter-cooled 1.6 l gasoline engine. A fast-response particulate spectrometer for exhaust nano-particle measurement up to 1000 nm was utilised. It was observed that the three-way catalytic converter had a significant effect on particle number density, reducing the total particle number by up to 65 % over the duration of the cold-start test. The greatest change in particle number density occurred for particles less than 23 nm diameter, with reductions of up to 95 % being observed, whilst the number density for particles above 50 nm diameter exhibited a significant increase. The exhaust temperature plays a significant role on the influence of the catalytic converter on the nano-scale particulate matter. It is evident that the dilution ratio of the exhaust sample has a distinct effect on the particulate matter number and size distribution, influencing the engine-out PM more significantly than the tailpipe-out PM during cold-start engine operation. The catalytic converter also has a considerable effect on the estimated total particle mass.

Study of the PM Gas-Phase Filter Artifact Using a Setup for Mixing Diesel-Like Soot and Hydrocarbons

The filter artifact is a significant source of error in gravimetric measurements of particulate matter (PM) exhaust. However, only a few studies on the subject exist. Results from these studies show a large discrepancy mainly because the experiments were performed using real diesel vehicle exhaust with varying exhaust composition. In this study, a setup for mixing diesel-like soot and hydrocarbon vapor was constructed for generating a stable exhaust aerosol with adjustable composition. The particle size distribution of the diesel-fueled soot generator (GMD [geometric mean diameter] adjustable between 27 and 164 nm) was found to represent “real” exhaust particulate emission. This setup was applied for studying the filter artifact on Teflon-coated glass fiber filters using pentadecane as the hydrocarbon vapor. Experiments were performed using particle and hydrocarbon concentrations of 130–700 μg/m3 and 10–12 ppm, respectively. It was found that the particle concentration of the aerosol affects the filter ar...

Simultaneous improvement in both exhaust emissions and fuel consumption by means of Fischer–Tropsch diesel fuels

In recent years, paraffinic fuels have attracted attention because of their potential for reducing diesel exhaust emissions, mainly smoke or particulate matter emissions. One of the paraffinic fuels, a Fischer–Tropsch diesel fuel, was selected to demonstrate the lower exhaust emissions while improving fuel economy in this study. To examine the detailed effects of fuel specifications on diesel combustion and emissions, preliminarily tests for three Fischer–Tropsch fuels and a baseline diesel fuel were carried out with three diesel engines having different engine displacements. In addition, differences in combustion phenomena between Fischer–Tropsch fuels and the baseline diesel fuel were observed by means of a single-cylinder engine with optical access. From these findings, one of the tested engines was modified to improve both exhaust emissions and fuel consumption, simultaneously, dedicated to the use of neat Fischer–Tropsch fuels. The conversion efficiency of an oxides of nitrogen reduction catalyst has also been improved. The desirable properties of Fischer–Tropsch fuels for diesel combustion, namely high cetane number and absence of poly-aromatic hydrocarbon contents, have been fully utilized to enhance the conventional diesel combustion limits to show the possibility to achieve very low exhaust emissions with substantial improvement in fuel economy. The results of this study indicate not only the superior emission characteristics of the Fischer–Tropsch fuels, but also evidence that higher exhaust gas recirculation and lower excess air ratios will be a key concept of both engine and aftertreatment optimization for further fuel consumption improvement.

Modelling lubrication oil particle emissions from heavy-duty diesel engines

The impact of lubrication oil on particle exhaust emissions has attracted increasing attention as emissions of fuel-derived particles have been reduced. This paper presents a model for assessing the oil-related exhaust particle emissions of heavy-duty diesel engines. The model contains four sub-models describing the hydrocarbon, ash, carbon and sulphate particles. All sub-models were developed based on the results of a literature review, complemented by controlled engine tests to fill the knowledge gaps and verify assumptions where necessary. Exhaust after-treatment devices, such as diesel particulate filters, are not included in the model at this stage; in engines equipped with such devices, the modelling results could be used to assess the input of oil-related particulate matter into the exhaust after-treatment system or serve as a basis for further development. The modelling results indicate that the contribution of oil to airborne exhaust particles is substantial under low-load and motoring conditions. Reducing oil consumption is an effective way to reduce oil-related particle emissions.

Online characterization of regulated and unregulated gaseous and particulate exhaust emissions from two-stroke mopeds: A chemometric approach

Two-stroke mopeds are a popular and convenient mean of transport in particular in the highly populated cities. These vehicles can emit potentially toxic gaseous and aerosol pollutants due to their engine technology. The legislative measurements of moped emissions are based on offline methods; however, the online characterization of gas and particulate phases offers great possibilities to understand aerosol formation mechanism and to adapt future emission standards. The purpose of this work was to study the emission behavior of two mopeds complying with different European emission standards (EURO-1 and EURO-2). A sophisticated set of online analyzers was applied to simultaneously monitor the gas phase and particulate phase of exhaust on a real time basis. The gaseous emission was analyzed with a high resolution Fourier transform infrared spectrometer (FTIR; nitrogen species) and a resonance-enhanced multiphoton ionization time-of-flight mass spectrometer (REMPI-ToF-MS; polycyclic aromatic hydrocarbons: PAH), whereas the particulate phase was chemically characterized by a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS; organic, nitrate and chloride aerosol) and a multiangle absorption photometer (MAAP; black carbon). The physical characterization of the aerosol was carried out with a condensation particle counter (CPC; particle number concentration) and a fast mobility particle sizer (FMPS; size distribution in real time). In order to extract underlying correlation between gas and solid emissions, principal component analysis was applied to the comprehensive online dataset. Multivariate analysis highlighted the considerable effect of the exhaust temperature on the particles and heavy PAH emissions. The results showed that the after-treatment used to comply with the latest EURO-2 emission standard may be responsible for the production of more potentially harmful particles compared to the EURO-1 moped emissions.

Effect of Fuel Injection Pressure on a Heavy-Duty Diesel Engine Nonvolatile Particle Emission

The effects of the fuel injection pressure on a heavy-duty diesel engine exhaust particle emissions were studied. Nonvolatile particle size distributions and gaseous emissions were measured at steady-state engine conditions while the fuel injection pressure was changed. An increase in the injection pressure resulted in an increase in the nonvolatile nucleation mode (core) emission at medium and at high loads. At low loads, the core was not detected. Simultaneously, a decrease in soot mode number concentration and size and an increase in the soot mode distribution width were detected at all loads. Interestingly, the emission of the core was independent of the soot mode concentration at load conditions below 50%. Depending on engine load conditions, growth of the geometric mean diameter of the core mode was also detected with increasing injection pressure. The core mode emission and also the size of the mode increased with increasing NOx emission while the soot mode size and emission decreased simultaneously.

Particle Emissions From Rail Traffic: A Literature Review

Particle emissions are a drawback of rail transport. This work is a comprehensive presentation of recent research into particle emissions from rail vehicles. Both exhaust and nonexhaust particle emissions are considered when examining particle characteristics such as PM10, and PM2.5 concentration levels, size, morphology, composition, and adverse health effects, current legislation, and available and proposed solutions for reducing such emissions. High concentration levels in enclosed rail traffic environments are reported and some toxic effects of the particles. The authors find that only a few limited studies have examined the adverse health effects of nonexhaust particle emissions and that no relevant legislation exists. Thus further research in this area is warranted.

Emissions of Particulate Trace Elements, Metals and Organic Species from Gasoline, Diesel, and Biodiesel Passenger Vehicles and Their Relation to Oxidative Potential

Three light-duty passenger vehicles were tested in five configurations in a chassis dynamometer study to determine the chemical and oxidative potential of the particulate exhaust emissions. The first vehicle was a diesel Honda with a three-stage oxidation system. Its main catalyst was replaced with a diesel particulate filter (DPF) and tested as a second configuration. The second vehicle was a gasoline-fuelled Toyota Corolla with a three-way catalytic converter. The last vehicle was an older Volkswagen Golf, tested using petro-diesel in its original configuration, and biodiesel with an oxidation catalyst as an alternative configuration. Particulate matter (PM) was collected on filters and subsequently analyzed using various chemical and toxicological assays. The production of reactive oxygen species (ROS), quantified by the dithiothreitol (DTT) and macrophage-ROS assays, was used to measure the PM-induced oxidative potential. The results showed that the Golf vehicle in both configurations had the highest ...

Effect of a Cetane Number (CN) Improver on Combustion and Emission Characteristics of a Compression-Ignition (CI) Engine Fueled with an Ethanol−Diesel Blend

Ethanol−diesel blended fuel has the potential to reduce diesel engine exhaust smoke and particulate emission as well as partially solve the energy crisis. However, with the increase of the ethanol fraction of the blends, the engine combustion will be affected significantly because of the change of fuel properties, especially the ignition delay (τig). Generally, a cetane number (CN) improver should be added to improve the engine combustion. In this study, E30 (30 vol % of ethanol in the blend) was prepared. A CN improver was added at 0, 0.3, and 0.6% (in volume), respectively. With a two-cylinder diesel engine, the effects of a CN improver on the engine combustion and emissions were investigated. Experimental results show that, in comparison to the diesel engine, the brake thermal efficiency of the E30 engine is improved, the τig is prolonged, while the total combustion duration becomes shorter. With the increase of the CN improver fraction, the brake thermal efficiency, diffusive combustion phase, and total combustion duration all increase, while the τig decreases. The addition of ethanol and a CN improver in diesel has no effect on nitric oxides (NOx); however, the particulate matter (PM) and smoke emissions of the E30 engine decrease significantly, and they will be deteriorated with a high fraction blending of a CN improver.