Teresa L Barone

Novel Characterization of GDI Engine Exhaust for Gasoline and Mid- Level Gasoline-Alcohol Blends

Gasoline direct injection (GDI) engines can offer improved fuel economy and higher performance over their port fuelinjected (PFI) counterparts, and are now appearing in increasingly more U.S. and European vehicles. Small displacement, turbocharged GDI engines are replacing large displacement engines, particularly in light-duty trucks and sport utility vehicles, in order for manufacturers to meet more stringent fuel economy standards. GDI engines typically emit the most particulate matter (PM) during periods of rich operation such as start-up and acceleration, and emissions of air toxics are also more likely during this condition. A 2.0 L GDI engine was operated at lambda of 0.91 at typical loads for acceleration (2600 rpm, 8 bar BMEP) on three different fuels; an 87 anti-knock index (AKI) gasoline (E0), 30% ethanol blended with the 87 AKI fuel (E30), and 48% isobutanol blended with the 87 AKI fuel. E30 was chosen to maximize octane enhancement while minimizing ethanol-blend level and iBu48 was chosen to match the same fuel oxygen level as E30. Particle size and number, organic carbon and elemental carbon (OC/EC), soot HC speciation, and aldehydes and ketones were all analyzed during the experiment. A new method for soot HC speciation is introduced using a direct, thermal desorption/pyrolysis inlet for the gas chromatograph (GC). Results showed high levels of aromatic compounds were present in the PM, including downstream of the catalyst, and the aldehydes were dominated by the alcohol blending.

Toward Developing a New Occupational Exposure Metric Approach for Characterization of Diesel Aerosols

The extensive use of diesel-powered equipment in mines makes the exposure to diesel aerosols a serious occupational issue. The exposure metric currently used in U.S. underground noncoal mines is based on the measurement of total carbon (TC) and elemental carbon (EC) mass concentration in the air. Recent toxicological evidence suggests that the measurement of mass concentration is not sufficient to correlate ultrafine aerosol exposure with health effects. This urges the evaluation of alternative measurements. In this study, the current exposure metric and two additional metrics, the surface area and the total number concentration, were evaluated by conducting simultaneous measurements of diesel ultrafine aerosols in a laboratory setting. The results showed that the surface area and total number concentration of the particles per unit of mass varied substantially with the engine operating condition. The specific surface area (SSA) and specific number concentration (SNC) normalized with TC varied two and five times, respectively. This implies that miners, whose exposure is measured only as TC, might be exposed to an unknown variable number concentration of diesel particles and commensurate particle surface area. Taken separately, mass, surface area, and number concentration did not completely characterize the aerosols. A comprehensive assessment of diesel aerosol exposure should include all of these elements, but the use of laboratory instruments in underground mines is generally impracticable. The article proposes a new approach to solve this problem. Using SSA and SNC calculated from field-type measurements, the evaluation of additional physical properties can be obtained by using the proposed approach. Copyright 2012 American Association for Aerosol Research

An Analysis of Field-Aged Diesel Particulate Filter Performance: Particle Emissions before, during, and after Regeneration

Abstract A field-aged, passive diesel particulate filter (DPF) used in a school bus retrofit program was evaluated for emissions of particle mass and number concentration before, during, and after regeneration. For the particle mass measurements, filter samples were collected for gravimetric analysis with a partial flow sampling system, which sampled proportionally to the exhaust flow. A condensation particle counter and scanning mobility particle sizer measured total number concentration and number-size distributions, respectively. The results of the evaluation show that the number concentration emissions decreased as the DPF became loaded with soot. However, after soot removal by regeneration, the number concentration emissions were approximately 20 times greater, which suggests the importance of the soot layer in helping to trap particles. Contrary to the number concentration results, particle mass emissions decreased from 6 ± 1 mg/hp-hr before regeneration to 3 ± 2 mg/hp-hr after regeneration. This indicates that nanoparticles with diameters less than 50 nm may have been emitted after regeneration because these particles contribute little to the total mass. Overall, average particle emission reductions of 95% by mass and 10,000-fold by number concentration after 4 yr of use provided evidence of the durability of a field-aged DPF. In contrast to previous reports for new DPFs in which elevated number concentrations occurred during the first 200 sec of a transient cycle, the number concentration emissions were elevated during the second half of the heavy-duty Federal Test Procedure (FTP) when high speed was sustained. This information is relevant for the analysis of mechanisms by which particles are emitted from field-aged DPFs.

Diesel Oxidation Catalyst Control of Hydrocarbon Aerosols From Reactivity Controlled Compression Ignition Combustion

Reactivity Controlled Compression Ignition (RCCI) is a novel combustion process that utilizes two fuels with different reactivity to stage and control combustion and enable homogeneous combustion. The technique has been proven experimentally in previous work with diesel and gasoline fuels; low NOx emissions and high efficiencies were observed from RCCI in comparison to conventional combustion. In previous studies on a multi-cylinder engine, particulate matter (PM) emission measurements from RCCI suggested that hydrocarbons were a major component of the PM mass. Further studies were conducted on this multi-cylinder engine platform to characterize the PM emissions in more detail and understand the effect of a diesel oxidation catalyst (DOC) on the hydrocarbon-dominated PM emissions. Results from the study show that the DOC can effectively reduce the hydrocarbon emissions as well as the overall PM from RCCI combustion. The bimodal size distribution of PM from RCCI is altered by the DOC which reduces the smaller mode 10 nm size particles.

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

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

FUNGIBLE AND COMPATIBLE BIOFUELS: LITERATURE SEARCH, SUMMARY, AND RECOMMENDATIONS

The purpose of the study described in this report is to summarize the various barriers to more widespread distribution of bio-fuels through our common carrier fuel distribution system, which includes pipelines, barges and rail, fuel tankage, and distribution terminals. Addressing these barriers is necessary to allow the more widespread utilization and distribution of bio-fuels, in support of a renewable fuels standard and possible future low-carbon fuel standards. These barriers can be classified into several categories, including operating practice, regulatory, technical, and acceptability barriers. Possible solutions to these issues are discussed; including compatibility evaluation, changes to bio-fuels, regulatory changes, and changes in the distribution system or distribution practices. No actual experimental research has been conducted in the writing of this report, but results are used to develop recommendations for future research and additional study as appropriate. This project addresses recognized barriers to the wider use of bio-fuels in the areas of development of codes and standards, industrial and consumer awareness, and materials compatibility issues.

Health Effects from Advanced Combustion and Fuel Technologies

This document requires a separate file for the figures. It is for DOEs Office of Vehicle Technologies Annual Report