Particulate Matter Mass Emissions Research Articles

Characterisation of particulates and trace metals emitted by a dimethyl ether-fuelled genset engine prototype

Diesel-fuelled CI engines are the primary sources of particulate matter (PM) emissions which harm human health and the urban environment. Elevated PM emission levels can cause respiratory diseases and deteriorate urban air quality and atmospheric visibility. DME, a carbon-neutral and oxygenated fuel, is fast merging as a strong alternative to diesel to reduce PM emissions. The absence of a direct carbon-carbon bond in the molecular structure of DME improves combustion and reduces PM emissions to negligible levels. DME and baseline diesel are experimentally evaluated in a single-cylinder CI genset engine prototype to find the particulate number-size, surface area-size and mass-size distributions. In addition, total particulate number (TPN), total particulate mass (TPM), count mean diameter (CMD) of particulates, particulate morphology and trace metals were assessed. DME genset engine emitted higher numbers of smaller diameter particles, with lower surface area and mass distribution than baseline diesel. For DME, total PM mass emission and CMD of particulates were lower due to particles being finer. Morphological analysis of particulates showed the presence of larger particles from diesel and less bunched agglomerates of nucleation mode particles from the DME genset engine prototype. The trace metal analysis of particulates showed higher presence of trace metals such as Si, Ca, and Na in DME-fuelled engine than in diesel. As an alternative to diesel, DME can reduce PM emissions from genset engines, significantly enhance urban air quality, and minimise the threat of respiratory diseases.

Fuel property impacts on gaseous and PM emissions from a multi-mode single-cylinder engine

The U.S. Department of Energy’s Co-Optima initiative has focused on improving fuel economy and vehicle performance while reducing emissions through the simultaneous development of emerging sustainable fuels with beneficial properties and advanced combustion strategies. A major thrust has been the development of advanced compression ignition (ACI) combustion strategies of gasoline range fuels in combination with spark-ignited (SI) combustion in a single engine capable of multi-mode operation to achieve high power density with enhanced part load efficiency. The aim of this study was to further the understanding of how emissions from both ACI and SI strategies operating on the same fuels in the same engine are impacted by different fuel properties. This investigation focused on particulate matter (PM) and gaseous hydrocarbon emissions from 6 different fuels across 3 different combustion modes on the same single-cylinder engine designed for multi-mode operation: SI combustion, partial fuel stratification (PFS), and spark-assisted compression ignition (SACI). In each of these modes, 3 different CA50 phasings were studied such that all 6 fuels could be studied at the same phasings. Three of the six different fuels used were specially formulated in a previous investigation to study the impact of fuel distillation and aromatic content while maintaining the research octane number (RON) and octane sensitivity. Additionally, neat isooctane and two ethanol containing fuels (RD5-87 and Co-Optima E30) were studied. Different fuel and phasing impacts on emissions were observed across the three combustion modes. Fuel properties were found to impact soot PM and particle number more than the CA50 phasing, while the phasing had more impact on NOx emissions. The NOx emissions were reduced in the PFS mode for all fuels compared to SI combustion, but the SACI combustion mode did not reduce NOx emissions. Although PFS produced low soot PM emissions like SI, total PM mass emissions were significantly higher due to large organic carbon (OC) PM mass contribution. Both PFS and SACI had greater particle number emission than SI operation with small nuclei mode particles dominating in PFS compared to large agglomeration particles in SACI.

The Impact of Composition in Non-steel and Low-Steel Type Friction Materials on Airborne Brake Wear Particulate Emission

In this work, airborne brake wear particulate matter (PM) emissions from a brake system were investigated by time-resolved and temperature-dependent measurement using a dynamometer. The measurement was performed for representative friction materials, 3 low-steel (LS) and 4 non-steel (NS), which are currently in worldwide use. The PM emission factor was found to be varied as large as by one order of magnitude depending on the composition of friction materials(pads). The airborne particle mass emissions from the LS materials ranged from 1.88 to 3.14 mg/km/vehicle, while the emissions from the NS ranged from 0.3 to 2.34 mg/km/vehicle, which is, in general, smaller than the LS. The time-resolved data imply that particle emissions in the extra-high-speed region of the WLTC cycle, where friction occurs at high temperature (Tdisk > 150 °C), is much higher than in the low-speed region, and determines the total PM mass emission factor. It was found that the friction materials containing metals such as Cu and Sn (LS-2/-3 and NS-4/-5) exhibited a lower PM emission factor. This result suggests that copper and tin, which forms an effective lubricating tribolayer in the interface between the pad and disk at high temperature, remarkably reduces PM emissions. It has been also found that the surface roughness of worn brake pads is positively proportional to PM emissions according to surface topography analysis, which is consistent with composition effect. These findings suggest that tribological engineering to provide sliding frictional behavior at elevated temperature is crucial to reducing PM emissions.

On-Road Portable Emission Measurement Systems Test Data Analysis and Light-Duty Vehicle In-Use Emissions Development

<div>Portable emission measurement systems (PEMS) [<span>1</span>] are used by the US Environmental Protection Agency (EPA) to measure gaseous and particulate matter mass emissions from vehicles in normal, in-use, on-the-road, and “real-world” operations to support many of its programs. These programs include vehicle modeling, emissions compliance, regulatory development, emissions inventory development, and investigations of the effects of real, in-use driving conditions on NOx, CO<sub>2</sub>, and other regulated pollutants.</div> <div>This article discusses EPA’s analytical methodology for evaluating light-duty vehicle energy and EU Real Driving Emissions (RDE). A simple, data-driven model was developed and validated using measured PEMS emissions test data. The work also included application of the EU RDE procedures and comparison to the PEMS test methodologies and FTP and other chassis dynamometer test data used by EPA for characterizing in-use light- and heavy-duty vehicle emissions. This work was conducted as part of EPA’s participation in the development of UNECE Global Technical Regulations and also supports EPA mobile source emission inventory development. This article discusses the real-world emissions of light-duty vehicles with 12V Start-Stop technology and light-duty vehicles using both gasoline and diesel fuels.</div>

Practical design considerations for secondary air injection in wood-burning cookstoves: An experimental study

Billions of households worldwide cook using biomass fires and suffer from the toxic smoke emitted into their homes. Laboratory studies of wood-burning cookstoves demonstrate that secondary air injection can greatly reduce the emission of harmful air pollution, but these experimental advancements are not easily translated into practical cookstove designs that can be widely adopted. In this study, we use a modular cookstove platform to experimentally quantify the practical secondary air injection design requirements (e.g., flow rate, pressure, and temperature) to reduce mass emissions of particulate matter (PM), carbon monoxide (CO), and black carbon (BC) by at least 90% relative to a traditional cooking fire. Over the course of 111 experimental trials, we illuminate the physical mechanisms that drive emission reductions, and outline fundamental design principles to optimize cookstove performance. Using the experimental data, we demonstrate that low-cost (<$10) fans and blowers are available to drive the secondary flow, and can be independently powered using an inexpensive thermoelectric generator mounted nearby. Furthermore, size-resolved PM measurements show that secondary air injection inhibits particle growth, but the total number of particles generated remains relatively unaffected. We discuss the potential impacts for human health and investigate methods to mitigate the PM formation mechanisms that persist.

INVESTIGATION OF THE ACCURACY PARTIAL-FLOW CONTROL SYSTEMS FOR PARTICULATE EMISSIONS FROM DIESEL EXHAUST GASES

The work is devoted to solving the problem of ensuring the required accuracy of frequent-flow mini- and microtunnels - compact systems for controlling mass emissions of particulate matter from diesel engines, which arises due to the difference in temperature conditions of sample preparation in these tunnels and the reference measurement system - full-flow tunnel. According to the results of the analysis of regulatory documents - UNECE Rules R-49, R-96, international standard ISO 8178 and others, international and domestic experience in the use of dilution tunnels, it was established: technical characteristics and operating conditions of reference full-flow and part-flow tunnels, empirical dependencies characterizing the degree the influence of the sample temperature of diluted exhaust gases in the tunnel on the accuracy of measurements of mass emissions of particulate matter at various diesel operating modes. Mathematical models have been developed to determine: sample temperatures in tunnels of various types, the resulting measurement error of the average operational emission of particulate matter - PM index, taking into account the influence of sample temperature in the tunnel on the accuracy of PM measurements. Based on the results of tests of 1Ч12/14 and 4ЧН12/14 diesel engines according to the ESC cycle and developed mathematical models, computational studies were carried out to assess the impact on the accuracy of the minitunnel and microtunnel with diameters of 10 cm and 3 cm, respectively, of the temperature conditions of sample preparation, which were compared with a reference system with diameter, 46 cm. The research results proved the feasibility of controlling the temperature of the sample in the microtunnel to eliminate significant methodological errors in the measurement of PM, which are -1.6 ... -1.7%. In a minitunnel, the corresponding errors are not significant and equal to -0.3 ... -0.4%. Since the thermal conditions for diluting the exhaust gases in the minitunnel and the reference system are approximately equal, there is no need to control the sample temperature in this system.

Characterization of the Fine Particle Emissions from the Use of Two Fischer-Tropsch Fuels in a CFM56-2C1 Commercial Aircraft Engine.

The fine particulate matter (PM) emissions from the use of two types of Fischer-Tropsch aviation fuels and their 50:50 blends with military JP-8 were quantified as part of the first Alternative Aviation Fuel Experiment (AAFEX). Measurements were made at 30-m downstream of a CFM56-2C1 engine for PM mass and number, particle size distribution, black carbon (BC), and volatile PM (sulfate + organics) using selected on-line instrumentation. The PM number emission index (EI N ) ranged from ~ 2 × 1015 to 7 × 1016 particles/kg fuel burned depending on fuel flow, fuel composition, and sampling temperature with the magnitude of the emissions inversely correlated to fuel flow. The PM mass emissions (EI M ) measured in the study varied from ~ 5 to 680 mg/kg fuel again depending on fuel flow, fuel type, and sampling temperature with a characteristic U-shaped curve of EI M with respect to fuel flow observed from the data. At low fuel flow (corresponding to low engine power), particle number and volume size distributions contained a single mode whereas at higher engine power, a bi-modal distribution was observed. The BC emissions varied from ~ 3 to 415 mg/kg fuel depending on fuel type and were found to exponentially increase with engine power (fuel flow). The volatile PM varied with sample temperature, fuel type, and increasing fuel flow within the range of EIs from ~ 0.4 to 11 mg/kg fuel with the highest values being at low fuel flow. Finally, the use of the two neat alternative fuels reduced the EI N by a median value of 70-73% and the EI M by ~ 94% as compared to JP-8 across all power conditions tested.

Particulate Emissions of Euro 4 Motorcycles and Sampling Considerations

The scientific literature indicates that solid particle number (SPN) emissions of motorcycles are usually higher than that of passenger cars. The L-category (e.g., mopeds, motorcycles) Euro 4 and 5 environmental steps were designed to reduce the emissions of particulate matter and ozone precursors such as nitrogen oxides and hydrocarbons. In this study the SPN emissions of one moped and eight motorcycles, all fulfilling the Euro 4 standards, were measured with a SPN measurement system employing a catalytic stripper to minimize volatile artefacts. Although the particulate matter mass emissions were &lt;1.5 mg/km for all vehicles tested, two motorcycles and the moped were close to the SPN limit for passenger cars (6 × 1011 particles/km with sizes larger than 23 nm) and four motorcycles exceeded the limit by a factor of up to four. The measurement repeatability was satisfactory (deviation from the mean 10%) and concentration differences between tailpipe and dilution tunnel were small, indicating that performing robust SPN measurements for regulatory control purposes is feasible. However, steady state tests with the moped showed major differences between the tailpipe and the dilution tunnel sampling points for sub-23 nm particles. Thus, the measurement procedures of particles for small displacement engine mopeds and motorcycles need to be better defined for a possible future introduction in regulations.

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.

Emissions from a flex fuel GDI vehicle operating on ethanol fuels show marked contrasts in chemical, physical and toxicological characteristics as a function of ethanol content

This study assessed the gaseous and particulate emissions, as well as the toxicological properties of particulate matter (PM) from a flex fuel vehicle equipped with a wall-guided gasoline direct injection engine over triplicates cold-start and hot-start LA92 cycles. The vehicle was operated on a Tier 3 E10 fuel, an E10 fuel with higher levels of aromatics than the Tier 3 E10, an E30, and an E78 blend. Total hydrocarbon (THC), non-methane hydrocarbon (NMHC), carbon monoxide (CO), particulate emissions, and gaseous toxics (of benzene, toluene, ethylbenzene, xylenes (BTEX), and 1,3-butadiene) reduced for E30 and E78 blends compared to both E10 fuels. Formaldehyde and acetaldehyde emissions substantially increased with the higher ethanol blends. The high aromatic E10 fuel increased the emissions of THC, NMHC, particulates, and BTEX compared to the Tier 3 E10 fuel and the higher ethanol blends, as well as showed higher concentrations of accumulation mode particles. The GDI PM did not exhibit any measurable mutagenicity at the PM concentrations tested. Cytotoxicity varied only within a small range and concentrations of PM, eliciting a cytotoxic response similar to those by ambient aerosol. The outcomes of our two measures of PM oxidative potential (macrophage ROS and DTT) were significantly correlated, with the E78 blend exhibiting the least oxidative potential and the E30 the greatest. Gene expression analysis at both the mRNA and protein level indicates that there is the potential for GDI PM emissions to contribute to inflammation and etiology of disease such as asthma, and in contrast to the ROS and DTT outcomes, the E78 fuel PM exhibited the greatest potential to elicit pro-inflammatory cytokine (TNFα) production. Overall, the trends in toxicity emission rates (activity/mi) across the ethanol blends was driven primarily by PM mass emission rate contrasts and only secondarily by the differences in intrinsic toxicity of the PM.

A reduced PM index for evaluating the effect of fuel properties on the particulate matter emissions from gasoline vehicles

Particulate matter (PM) emissions have become an increasingly noticeable concern for gasoline vehicles, especially for gasoline direct injection (GDI) one. The PM index (PMI) model developed by Aikiwa et al. provides an effective model linking the fuel properties to the PM emissions from gasoline vehicles. In this study, a more practical reduced PM index (RPMI) was developed based on the detailed analysis of 22 fuels with various physical properties and chemical compositions. Two approaches of statistical mathematics of correlation analysis and multivariate linear regression (MLR) were adopted in the modeling process. The RPMI involving two global fuel properties of T90 (distillation temperature of 90% by volume) and T70 (distillation temperature of 70% by volume) was tested to be statistically valid. In addition, the model was verified through the engine bench tests and the vehicle emissions tests. The results reveal that the RPMI showed good correlations to the engine-out particle number (PN) emissions under all of the typical test conditions, including PFI (port fuel injection) mode, GDI (gasoline direct injection) mode and compound injection (PFI + GDI) mode. In addition, the RPMI demonstrated a significantly high correlation to vehicle-out PN emissions over the New European Driving Cycle (NEDC) with the determination coefficient R2 = 0.947. Moreover, a moderate correlation (R2 = 0.801) of the index to the filter PM mass emissions was observed. In the light of no additional components analysis is needed except for the legitimate tests of fuels, the RPMI has the potential to be a useful tool for original equipment manufacturers (OEMs) and environmental certification departments to expediently evaluate the fuel effect on PM emissions.

How do particle number, surface area, and mass correlate with toxicity of diesel particle emissions as measured in chemical and cellular assays?

Increasingly stringent particulate matter (PM) emission standards have brought forth engine design improvements, cleaner-burning fuels, and aftertreatment technologies. Reductions in tailpipe PM mass have concomitantly reduced accumulation-mode particle emissions. However, some strategies promote the emission of nucleation-mode particles, which are typically quantified on a number (PN) basis. We previously demonstrated that PN emissions from heavy-duty diesel vehicles equipped with various aftertreatment systems were inversely correlated, and gravimetric PM mass was positively correlated, with two in vitro assays. This present work expands on the analysis of PM mass and PN with in vitro assays to also include four additional PM metrics: suspended PM mass, active particle surface area, aggregate particle surface area, and accumulation-mode particle number. This new analysis shows that like gravimetric PM mass, suspended particle mass and accumulation mode particle number are well correlated with dithiothreitol consumption rate (DTT) and macrophage reactive oxygen species consumption rate (ROS) assays (R2 = 0.61–0.96). Data suggest that PM mass emissions dominated by nucleation-mode particles induce equal or slightly greater toxicity compared to PM mass dominated by accumulation-mode particles. Data also show that among all PM metrics, those used for regulating PM in the United States and Europe, namely gravimetric mass and solid PN are overall most correlated with in vitro toxicity. Moreover, continued exploration of alternative, low-cost, and more appropriate PM metrics is warranted to better understand the reproducibility of these findings on other engine applications, fuel types, and aftertreatment platforms.

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.

Experimental Study of Particulate Emission Characteristics from A Gasoline Direct Injection Engine During Starting Process

The engine starting process presents high particulate emissions in exhaust. This study gives a systematic investigation on particulate emission characteristics, including particulate matter (PM) mass, soluble organic fraction (SOF) mass, C10-C26 n-Alkanes and particle-bound polycyclic aromatic hydrocarbons (PAHs), that have been emitted from a gasoline direct injection (GDI) engine measured by Gas chromatography-mass spectrometry during starting period. The results show that particulate emissions under the warm coolant start condition decline dramatically compared with the cold start condition. 90 % of particulate number (PN) emitted during the cold and warm start periods generally are nucleation-mode particles. Over 50 % PM mass and PAHs emissions are emitted in the first 0–13 s stage. SOF mass accounts more than 60 % in PM mass emissions, especially under the warm coolant start condition. Some C23–C26 n-Alkanes are detected under the cold start condition which demonstrates that partial particulate composition directly comes from lubricant. The concentration of the two ring PAHs is the lowest among PAHs while the four to six ring PAHs are higher under the cold start operation. The toxicity of PAHs which is evaluated by Benzo(a)pyrene equivalent toxicity (BEQ) value of the total PAHs emissions shows a decline of 66.83 % under the warm start condition.

Fixed Bed Combustion of Biomass: Particulate Matter Mitigation by Optimising Temperature and Fuel Particle Size

Experimental results are presented on the particulate matter emissions from a fixed bed combustion reactor chamber combusting two types of ambient dried biomass fuels, six different particle sizes (0.044-0.149mm) in seven different temperature zones (600-1200 ºC).The fuel was ground into various particle sizes and the temperature of combustion was varied for investigation on the emission due from the various parameters. Measurements were made for particulate matter (PM) during the whole phase of combustion by a portable soot analyzer. The PM investigated here is total catch that includes solid particles of elemental carbon and fuel and condensed organic compounds due from incomplete combustion which are less than or equal to 10µm in aerodynamic diameter. The fuel was ground by a grinder and sieved into different sizes by a shake sieve with various mesh sizes. It was found that the PM emission from both biomass fuels was significantly dependent on the temperature of combustion which in turn dictated the residence time in the combustion chamber. The mean PM mass emissions from wood and peanut shell were established. The optimum combustion temperature was identified to be 900°C attracting PM mitigation of up to 63%. The least PM producing particle size for peanut shell and wood fuel was determined to be 0.149mm combusting at 12000C and 0.074mm combusting at 6000C respectively with capacity to mitigate PM production by a maximum of 30-49%. However the effect of the two parameters was established to be mutually dependent. The time taken for complete combustion reduced steadily with the increase of the temperature from 360 seconds at 600°C to 150 seconds at 1200°C.

Optimization of Secondary Air Injection in a Wood-Burning Cookstove: An Experimental Study.

Nearly 40% of the world's population regularly cooks on inefficient biomass stoves that emit harmful airborne pollutants, such as particulate matter (PM). Secondary air injection can significantly reduce PM mass emissions to mitigate the health and climate impacts associated with biomass cookstoves. However, secondary air injection can also increase the number of ultrafine particles emitted, which may be more harmful to health. This research investigates the effect of secondary air injection on the mass and size distribution of PM emitted during solid biomass combustion. An experimental wood-burning cookstove platform and parametric testing approach are presented to identify and optimize secondary air injection parameters that reduce PM and other harmful pollutants. Size-resolved measurements of PM emissions were collected and analyzed as a function of parametric stove design settings. The results show that PM emissions are highly sensitive to secondary air injection flow rate and velocity. Although increasing turbulent mixing (through increased velocity) can promote more complete combustion, increasing the total flow rate of secondary air may cause localized flame quenching that increases particle emissions. Therefore, biomass cookstoves that implement secondary air injection should be carefully optimized and validated to ensure that PM emission reductions are achieved throughout the particle size range.

Particulate Matter and Gaseous Emission of Hydrous Ethanol Gasoline Blends Fuel in a Port Injection Gasoline Engine

The industrialization that increases day by day needs more and more power/fuel sources that are commonly available, abundant, renewable, and environmentally friendly. Recently, nearly all of the cities in China (PRC) have been influenced by haze. However, the pollutants from automobiles have always been seriously considered to be the main contamination causes of the haze and that influence human health. This study concerns the impact of hydrous ethanol on in-cylinder pressure, particulate matter (PM), and gaseous emissions (oxides of nitrogen (NOx) and unburned hydrocarbon (HC)) from a port fuel injection (PFI) gasoline engine. Tests were conducted on a four-cylinder port injection gasoline engine at different engine loads at an engine speed of 2000 rev/min for commercial gasoline, hydrous ethanol-gasoline blends (10% and 20% hydrous ethanol by volume), and an anhydrous ethanol-gasoline blend (20% anhydrous ethanol by volume). The results show that the peak in-cylinder pressure with the use of gasoline was the highest compared with the hydrous ethanol and anhydrous ethanol blends. Compared with the anhydrous ethanol blend, the hydrous ethanol blends performed well at a high load condition, equivalent to a low load. In addition, the total particulate number (PN) declines with an increase in engine operating loads for all of the fuels tested. The outcome of this study is an important reduction in PM number, mass emissions, and mean diameters of particles as the use of hydrous ethanol blends increases, while the form of the particulate size distribution remains the same. Furthermore, the NOx emission is raised with a rise in engine load, and NOx and HC emissions are reduced with the use of hydrous ethanol and anhydrous ethanol blend as equated with pure gasoline. Moreover, the correlation between the total particle number against NOx and HC has been found; the number of particles increases when the NOx emission decreases, and the opposite trend is exhibited for the HC emission. Therefore, it can be concluded that hydrous ethanol blends look to be a good selection for PM, NOx, and HC reduction for gasoline engines.

Investigation of alternative metrics to quantify PM mass emissions from light duty vehicles

We evaluated the performance of six alternative particulate matter (PM) metrics relative to the regulatory gravimetric method during chassis dynamometer testing of five light-duty vehicles over the Federal Test Procedure (FTP) and Supplemental FTP (US06) cycles. Alternative metrics included three mass-based metrics including black carbon (BC), two suspended PM mass using integrated particle size distribution (IPSD) method, and three number/surface-based metrics including total particle number (PN), solid particle number (SPN), and particle active surface area (PS). The results showed PM emissions over the FTP cycle were dominated by solid particles on a mass basis (BC to PM ratio = 0.6 ± 0.5), whereas over the US06 cycle were dominated by semi-volatile particles (BC to PM ratio = 0.2 ± 0.2). Moderate to strong correlations were reported between the gravimetric method and the six alternative metrics for FTP and US06 cycles separately (R2 = 0.69–0.91), i.e. the best-fit lines were strongly dependent upon the cycle. On the other hand, the six alternative PM mass and number metrics exhibited moderate to strong correlations regardless of the test cycle (R2 = 0.66–0.98). We attribute the observed cycle dependency between alternative metrics and the gravimetric mass method to the greater gravimetric sensitivity to organic and semi-volatile PM than for most alternative metrics.

Impact of aggressive drive cycles on motor vehicle exhaust PM emissions

Aggressive drive cycles can cause substantial discrepancies between particulate matter (PM) measurement methods and increased emissions variability. Previous work demonstrated good agreement, within ~10%, between aerosol instruments and gravimetric determinations of PM mass emissions from gasoline direct injection engine (GDI) vehicles run over the Federal Test Procedure (FTP). In contrast, the present study reveals discrepancies of a factor of three or more for these vehicles run over the US06 portion of the supplemental FTP test. Two aspects of this are examined: 1) Changes in particle composition and morphology and 2) variability associated with vehicle history and test preparation. PM emissions during the US06 cycle are often accompanied by a strong nucleation mode. The organic to elemental carbon ratio increases relative to the FTP cycle. Also, the black carbon to elemental carbon ratio decreases, suggesting the formation of brown soot. The origins of these changes are not entirely clear, but are likely associated with the high engine exhaust temperatures during the US06 cycle. This also contributes to the higher test to test variability observed for the US06 versus FTP cycle. High temperatures can thermally desorb and pyrolyze various materials, including heavy hydrocarbons, ash, and inorganic salts deposited in the exhaust pipe, catalytic converter, and muffler that provide an additional PM source not present during FTP driving. The first day’s PM mass emissions are often substantially higher than on following days for the US06 cycle, but not the FTP. There is also a distinct drop in PM emissions between first and subsequent US06 cycles run in series.

Comparison of Gasoline Direct-Injection (GDI) and Port Fuel Injection (PFI) Vehicle Emissions: Emission Certification Standards, Cold-Start, Secondary Organic Aerosol Formation Potential, and Potential Climate Impacts.

Recent increases in the Corporate Average Fuel Economy standards have led to widespread adoption of vehicles equipped with gasoline direct-injection (GDI) engines. Changes in engine technologies can alter emissions. To quantify these effects, we measured gas- and particle-phase emissions from 82 light-duty gasoline vehicles recruited from the California in-use fleet tested on a chassis dynamometer using the cold-start unified cycle. The fleet included 15 GDI vehicles, including 8 GDIs certified to the most-stringent emissions standard, superultra-low-emission vehicles (SULEV). We quantified the effects of engine technology, emission certification standards, and cold-start on emissions. For vehicles certified to the same emissions standard, there is no statistical difference of regulated gas-phase pollutant emissions between PFIs and GDIs. However, GDIs had, on average, a factor of 2 higher particulate matter (PM) mass emissions than PFIs due to higher elemental carbon (EC) emissions. SULEV certified GDIs have a factor of 2 lower PM mass emissions than GDIs certified as ultralow-emission vehicles (3.0 ± 1.1 versus 6.3 ± 1.1 mg/mi), suggesting improvements in engine design and calibration. Comprehensive organic speciation revealed no statistically significant differences in the composition of the volatile organic compounds emissions between PFI and GDIs, including benzene, toluene, ethylbenzene, and xylenes (BTEX). Therefore, the secondary organic aerosol and ozone formation potential of the exhaust does not depend on engine technology. Cold-start contributes a larger fraction of the total unified cycle emissions for vehicles meeting more-stringent emission standards. Organic gas emissions were the most sensitive to cold-start compared to the other pollutants tested here. There were no statistically significant differences in the effects of cold-start on GDIs and PFIs. For our test fleet, the measured 14.5% decrease in CO2 emissions from GDIs was much greater than the potential climate forcing associated with higher black carbon emissions. Thus, switching from PFI to GDI vehicles will likely lead to a reduction in net global warming.