Regulated and Non-Regulated Emissions from In-Use Diesel-Electric Switching Locomotives

Diesel-electric locomotives are vital to the operation of freight railroads in the United States, and emissions from this source category have generated interest in recent years. They are also gaining attention as an important emission source under the larger set of nonroad sources, both from a regulated emissions and health effects standpoint. The present work analyzes regulated (NOx, PM, THC, CO) and non-regulated emissions from three in-use diesel-electric switching locomotives using standardized sampling and analytical techniques. The engines tested in this work were from 1950, 1960, and 1970 and showed a range of NOx and PM emissions. In general, non-regulated gaseous emissions showed a sharp increase as engines shifted from non-idle to idle operating modes. This is interesting from an emissions perspective since activity data shows that these locomotives spend around 60% of their time idling. In terms of polycyclicaromatic hydrocarbon (PAH) contributions, the dominance of naphthalene and its derivatives over the total PAH emissions was apparent, similar to observations for on-road diesel tractors. Among non-naphthalenic species, it was observed that lower molecular weight PAHs and n-alkanes dominated their respective compound classes. Regulated emissions from a newer technology engine used in a back-up generator (BUG) application were also compared against the present engines; it was determined that use of the newer engine may lower NOx and PM emissions by up to 30%. Another area of interest to regulators is better estimation of the marine engine inventory for port operations. Toward that end, a comparison of emissions from these engines with engine manufacturer data and the newer technology BUG engine was also performed for a marine duty cycle, another application where these engines are used typically with little modifications

Quantifying In-Use PM Measurements for Heavy Duty Diesel Vehicles

Heavy duty emissions regulations have recently expanded from the laboratory to include in-use requirements. This paradigm shift to in-use testing has forced the development of portable emissions measurement systems (PEMS) for particulate matter (PM). These PM measurements are not trivial for laboratory work, and are even more complex for in-use testing. This study evaluates five PM PEMS in comparison to UCR’s mobile reference laboratory under in-use conditions. Three on-highway, heavy-duty trucks were selected to provide PM emissions levels from 0.1 to 0.0003 g/hp-h, with varying compositions of elemental carbon (EC), organic carbon (OC), and sulfate. The on-road driving courses included segments near sea level, at elevations up to 1500 m, and coastal and desert regions. The photoacoustic measurement PEMS performed best for the non-aftertreatment system (ATS)-equipped engine, where the PM was mostly EC, with a linear regression slope of 0.91 and an R2 of 0.95. The PEMS did not perform as well for the 2007 modified ATS equipped engines. The best performing PEMS showed a slope of 0.16 for the ATS-equipped engine with predominantly sulfate emissions and 0.89 for the ATS-equipped engine with predominantly OC emissions, with the next best slope at 0.45 for the predominantly OC engine

Evaluation of the Impacts of Biodiesel and Second Generation Biofuels on NO_x Emissions for CARB Diesel Fuels

The impact of biodiesel and second generation biofuels on nitrogen oxides (NO_<i>x</i>) emissions from heavy-duty engines was investigated using a California Air Resources Board (CARB) certified diesel fuel. Two heavy-duty engines, a 2006 engine with no exhaust aftertreatment, and a 2007 engine with a diesel particle filter (DPF), were tested on an engine dynamometer over four different test cycles. Emissions from soy- and animal-based biodiesels, a hydrotreated renewable diesel, and a gas to liquid (GTL) fuel were evaluated at blend levels from 5 to 100%. NO_<i>x</i> emissions consistently increased with increasing biodiesel blend level, while increasing renewable diesel and GTL blends showed NO_<i>x</i> emissions reductions with blend level. NO_<i>x</i> increases ranged from 1.5% to 6.9% for B20, 6.4% to 18.2% for B50, and 14.1% to 47.1% for B100. The soy-biodiesel showed higher NO_<i>x</i> emissions increases compared to the animal-biodiesel. NO_<i>x</i> emissions neutrality with the CARB diesel was achieved by blending GTL or renewable diesel fuels with various levels of biodiesel or by using di-<i>tert</i>-butyl peroxide (DTBP). It appears that the impact of biodiesel on NO_<i>x</i> emissions might be a more important consideration when blended with CARB diesel or similar fuels, and that some form of NO_<i>x</i> mitigation might be needed for biodiesel blends with such fuels

Evaluation of the Impacts of Biodiesel and Second Generation Biofuels on NO_x Emissions for CARB Diesel Fuels

The impact of biodiesel and second generation biofuels on nitrogen oxides (NO_<i>x</i>) emissions from heavy-duty engines was investigated using a California Air Resources Board (CARB) certified diesel fuel. Two heavy-duty engines, a 2006 engine with no exhaust aftertreatment, and a 2007 engine with a diesel particle filter (DPF), were tested on an engine dynamometer over four different test cycles. Emissions from soy- and animal-based biodiesels, a hydrotreated renewable diesel, and a gas to liquid (GTL) fuel were evaluated at blend levels from 5 to 100%. NO_<i>x</i> emissions consistently increased with increasing biodiesel blend level, while increasing renewable diesel and GTL blends showed NO_<i>x</i> emissions reductions with blend level. NO_<i>x</i> increases ranged from 1.5% to 6.9% for B20, 6.4% to 18.2% for B50, and 14.1% to 47.1% for B100. The soy-biodiesel showed higher NO_<i>x</i> emissions increases compared to the animal-biodiesel. NO_<i>x</i> emissions neutrality with the CARB diesel was achieved by blending GTL or renewable diesel fuels with various levels of biodiesel or by using di-<i>tert</i>-butyl peroxide (DTBP). It appears that the impact of biodiesel on NO_<i>x</i> emissions might be a more important consideration when blended with CARB diesel or similar fuels, and that some form of NO_<i>x</i> mitigation might be needed for biodiesel blends with such fuels

Development and Application of a Mobile Laboratory for Measuring Emissions from Diesel Engines. 2. Sampling for Toxics and Particulate Matter

Limited data are available on the emission rates of speciated volatile and semivolatile organic compounds, as well as the physical and chemical characteristics of fine particulate matter (PM) from mobile, in-use diesel engines operated on the road. A design for the sampling of these fractions and the first data from in-use diesel sources are presented in this paper. Emission rates for carbonyls, 1,3-butadiene, benzene, toluene, xylene, PM, and elemental and organic carbon (EC and OC) are reported for a vehicle driven while following the California Air Resources Board (ARB) four-mode heavy heavy-duty diesel truck (HHDDT) cycle and while transiting through a major transportation corridor. Results show that distance specific emission rates are substantially greater in congested traffic as compared with highway cruise conditions. Specifically, emissions of toxic compounds are 3−15 times greater, and PM is 7 times greater under these conditions. The dependence of these species on driving mode suggests that health and source apportionment studies will need to account for driving patterns in addition to emission factors. Comparison of the PM/NOx ratios obtained for the above tests provides insight into the presence and importance of “off-cycle” emissions during on-road driving. Measurements from a stationary source (operated and tested at constant engine speed) equipped with an engine similar to that in the HHDDT yielded a greater understanding of the relative dependence of emissions on load versus engine transients. These data are indicative of the type of investigations made possible by the development of this novel laboratory

Reduction of Particulate Matter Emissions from Diesel Backup Generators Equipped with Four Different Exhaust Aftertreatment Devices

Diesel particulate matter (PM) reduction efficiencies for backup generators (BUGs) (>300 kW) equipped with a diesel oxidation catalyst (DOC), DOC+fuel-borne catalyst additive combination (DOC+FBC), passive diesel particulate filter (DPF), and an active DPF were measured. Overall, the DOC and DOC+FBC technologies were found to be effective in reducing mainly organic carbon (OC) emissions (56−77%) while both DPFs showed excellent performance in reducing both elemental carbon (EC) and OC emissions (>90%). These findings demonstrate the potential for applying DOCs to older engines where PM is dominated by the OC fraction. In most modern engine applications, where the PM consists of mainly EC, the DOC will be largely ineffective. Alternatively, passive and active DPFs are expected to be efficient for most engine technologies. Measurements of particle size distributions provided evidence of the high temperature formation of sulfate nanoparticles across the control technologies despite the use of ultralow sulfur diesel. Changes in the particle size distribution and the organic fraction of PM indicate that the OC component of PM is primarily found in the smaller sized particles

Assessing the Impacts of Ethanol and Isobutanol on Gaseous and Particulate Emissions from Flexible Fuel Vehicles

This study investigated the effects of higher ethanol blends and an isobutanol blend on the criteria emissions, fuel economy, gaseous toxic pollutants, and particulate emissions from two flexible-fuel vehicles equipped with spark ignition engines, with one wall-guided direct injection and one port fuel injection configuration. Both vehicles were tested over triplicate Federal Test Procedure (FTP) and Unified Cycles (UC) using a chassis dynamometer. Emissions of nonmethane hydrocarbons (NMHC) and carbon monoxide (CO) showed some statistically significant reductions with higher alcohol fuels, while total hydrocarbons (THC) and nitrogen oxides (NO_<i>x</i>) did not show strong fuel effects. Acetaldehyde emissions exhibited sharp increases with higher ethanol blends for both vehicles, whereas butyraldehyde emissions showed higher emissions for the butanol blend relative to the ethanol blends at a statistically significant level. Particulate matter (PM) mass, number, and soot mass emissions showed strong reductions with increasing alcohol content in gasoline. Particulate emissions were found to be clearly influenced by certain fuel parameters including oxygen content, hydrogen content, and aromatics content

Comparison of Particle Mass and Solid Particle Number (SPN) Emissions from a Heavy-Duty Diesel Vehicle under On-Road Driving Conditions and a Standard Testing Cycle

It is important to understand the differences between emissions from standard laboratory testing cycles and those from actual on-road driving conditions, especially for solid particle number (SPN) emissions now being regulated in Europe. This study compared particle mass and SPN emissions from a heavy-duty diesel vehicle operating over the urban dynamometer driving schedule (UDDS) and actual on-road driving conditions. Particle mass emissions were calculated using the integrated particle size distribution (IPSD) method and called MIPSD. The MIPSD emissions for the UDDS and on-road tests were more than 6 times lower than the U.S. 2007 heavy-duty particulate matter (PM) mass standard. The MIPSD emissions for the UDDS fell between those for the on-road uphill and downhill driving. SPN and MIPSD measurements were dominated by nucleation particles for the UDDS and uphill driving and by accumulation mode particles for cruise and downhill driving. The SPN emissions were ∼3 times lower than the Euro 6 heavy-duty SPN limit for the UDDS and downhill driving and ∼4–5 times higher than the Euro 6 SPN limit for the more aggressive uphill driving; however, it is likely that most of the “solid” particles measured under these conditions were associated with a combination release of stored sulfates and enhanced sulfate formation associated with high exhaust temperatures, leading to growth of volatile particles into the solid particle counting range above 23 nm. Except for these conditions, a linear relationship was found between SPN and accumulation mode MIPSD. The coefficient of variation (COV) of SPN emissions of particles >23 nm ranged from 8 to 26% for the UDDS and on-road tests

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

Using a new inversion matrix for a fast-sizing spectrometer and a photo-acoustic instrument to determine suspended particulate mass over a transient cycle for light-duty vehicles

<p>Integrated particle size distribution (IPSD) is a promising alternative method for estimating particulate matter (PM) emissions at low levels. However, a recent light-duty vehicle (LDV) emissions study showed that particle mass estimated using IPSD (<i>M</i>_IPSD) with the TSI Engine Exhaust Particle Sizer (EEPS) Default Matrix was 56–75% lower than mass derived using the reference gravimetric method (<i>M</i>_Grav) over the Federal Test Procedure (FTP). In this study, <i>M</i>_IPSD calculated with a new inversion matrix, the Soot Matrix, is compared with <i>M</i>_Grav and also photoacoustic soot mass (<i>M</i>_Soot), to evaluate potential improvement of the IPSD method for estimating PM mass emissions from LDVs. In addition, an aerodynamic particle sizer (APS) was used to estimate mass emission rates attributed to larger particles (0.54–2.5 µm in aerodynamic diameter) that are not measured by the EEPS. Based on testing of 10 light-duty vehicles over the FTP cycle, the Soot Matrix significantly improved agreement between <i>M</i>_IPSD and <i>M</i>_Grav by increasing slopes of <i>M</i>_IPSD/<i>M</i>_Grav from 0.45–0.57 to 0.76–1.01 for gasoline direct injected (GDI) vehicles; however, for port-fuel injection (PFI) gasoline vehicles, a significant discrepancy still existed between <i>M</i>_IPSD and <i>M</i>_Grav, with <i>M</i>_IPSD accounting for 34 ± 37% of <i>M</i>_Grav. For all vehicles, strong correlations between <i>M</i>_IPSD and <i>M</i>_Soot were obtained, indicating the IPSD method is capable of capturing mass of soot particles. The discrepancy between the <i>M</i>_IPSD and <i>M</i>_Grav for PFI vehicles, which have relatively low PM emissions (0.22 to 1.83 mg/mile), could be partially due to limited size range of the EEPS by not capturing larger particles (0.54–2.5 µm) that accounts for ∼0.08 mg/mile of PM emission, uncertainties of particle effective density, and/or gas-phase adsorption onto filters that is not detected by <i>in situ</i> aerosol instrumentation.</p> <p>Copyright © 2016 American Association for Aerosol Research</p