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A major driving force for change in light-duty vehicle design and technology is the National Highway Traffic Safety Administration (NHTSA) and the U.S. Environmental Protection Agency (EPA) joint final rules concerning Corporate Average Fuel Economy (CAFE) and greenhouse gas (GHG) emissions for model years 2017 (MY17) through 2025 (MY25) passenger cars and light trucks. The chief goal of this current study is to compare the already rapid pace of fuel economy improvement and technological change over the previous decade to the required rate of change to meet regulations over the next decade. EPA and NHTSA comparisons of the model year 2005 (MY05) US light-duty vehicle fleet to the model year 2015 (MY15) fleet shows improved fuel economy (FE) of approximately 26% using the same FE estimating method mandated for CAFE regulations. Future predictions by EPA and NHTSA concerning ensemble fleet fuel economy are examined as an indicator of required vehicle rate-of-change.

The goal of this project was to demonstrate a low emissions, high efficiency heavy-duty on-highway natural gas engine. The emissions targets for this project are to demonstrate US 2010 emissions standards on the 13-mode steady state test. To meet this goal, a chemically correct combustion (stoichiometric) natural gas engine with exhaust gas recirculation (EGR) and a three way catalyst (TWC) was developed. In addition, a Sturman Industries, Inc. camless Hydraulic Valve Actuation (HVA) system was used to improve efficiency. A Volvo 11 liter diesel engine was converted to operate as a stoichiometric natural gas engine. Operating a natural gas engine with stoichiometric combustion allows for the effective use of a TWC, which can simultaneously oxidize hydrocarbons and carbon monoxide and reduce NOx. High conversion efficiencies are possible through proper control of air-fuel ratio.

Exhaust gas recirculation (EGR) cooler fouling has emerged as an important issue in diesel engine development. Uncertainty about the level of impact that fuel chemistry may have upon this issue has resulted in a need to investigate the cooler fouling process with emerging non-traditional fuel sources to gage their impact on the process. This study reports experiments using both ultra-low sulfur diesel (ULSD) and 20% biodiesel (B20) at elevated exhaust hydrocarbon conditions to investigate the EGR cooler fouling process. The results show that there is little difference between the degradation in cooler effectiveness for ULSD and B20 at identical conditions. At lower coolant temperatures, B20 exhibits elevated organic fractions in the deposits compared with ULSD, but this does not appear to lead to incremental performance degradation under the conditions studied.

High-speed diagnostics capable of accurately resolving emission transients are required to provide the most detailed understanding and optimization of active exhaust-emissions-treatment processes, such as NOX adsorbers. A portable, mass-spectrometry-based instrument with high temporal resolution, linear response and broad dynamic range is described. This instrument provides transient-concentration measurement capability for many relevant exhaust species including total NOX. In applications for evaluation of NOX-adsorber systems using heavy-duty diesel engines, the instrument revealed relevant emission transients not previously resolved with conventional analyzers. Specifically, the instrument resolved transient emissions associated with the competition between desorption and reduction rates. The temporal resolution of the instruments is sufficient to resolve kinetic rates of the NOX-adsorber system.

Due to its high efficiency and superior durability the diesel engine is again becoming a prime candidate for future light-duty vehicle applications within the United States. While in Europe the overall diesel share exceeds 40%, the current diesel share in the U.S. is 1%. Despite the current situation and the very stringent Tier 2 emission standards, efforts are being made to introduce the diesel engine back into the U.S. market. In order to succeed, these vehicles have to comply with emissions standards over a 120,000 miles distance while maintaining their excellent fuel economy. The availability of technologies such as high-pressure common-rail fuel systems, low sulfur diesel fuel, NOx adsorber catalysts (NAC), and diesel particle filters (DPFs) allow the development of powertrain systems that have the potential to comply with the light-duty Tier 2 emission requirements. In support of this, the U.S.

In this research, small, single cylinder engines have been used to simulate larger engines in the areas of aftertreatment, combustion, and fuel formulation effects. The use of small engines reduces overall research cost and allows more rapid experiments to be run. Because component costs are lower, it is also possible to investigate more variations and to sacrifice components for materials characterization and for subsequent experiments. Using small engines in this way is very successful in some cases. In other cases, limitations of the engines influence the results and need to be accounted for in the experimental design and data analysis. Some of the results achieved or limitations found may be of interest to the small engine market, and this paper is offered as a summary of the authors' research in these areas. Research is being conducted in two areas. First, small engines are being used to study the rapid aging and poisoning of exhaust aftertreatment catalysts.

It is widely recognized that future NOx and particulate matter (PM) emission targets for diesel engines cannot be met solely via advanced combustion over the full engine drive cycle. Therefore some combination of advanced combustion and aftertreatment technologies will be required. In this study, advanced combustion modes operating with a diesel particulate filter (DPF) and a lean NOx trap (LNT) catalyst were evaluated on a 1.7 liter 4-cylinder diesel engine. The combustion approaches included baseline engine operation with and without exhaust gas recirculation (EGR) and one PCCI-type (premixed charge combustion ignition) combustion mode to enable high efficiency clean combustion (HECC). Five steady-state operating conditions were evaluated. At the low load setting the exhaust temperature was too low to enable LNT regeneration and oxidation; however, HECC (low NOx) was achievable.

This study investigated the effects of soybean- and coconut-derived biodiesel fuels on combustion characteristics in a 1.7-liter direct injection, common rail diesel engine. Five sets of fuels were studied: 2007 ultra low sulfur diesel (ULSD), 5% and 20% volumetric blends of soybean biodiesel with ULSD (soybean B5 and B20), and 5% and 20% volumetric blends of coconut biodiesel with ULSD (coconut B5 and B20). In conventional diesel combustion mode, particulate matter (PM) and nitrogen oxides (NOx) emissions were similar for all fuels studied except soybean B20. Soybean B20 produced the lowest PM but the highest NOx emissions. Compared with conventional diesel combustion mode, high efficiency clean combustion (HECC) mode, achieved by increased EGR and combustion phasing, significantly reduced both PM and NOx emissions for all fuels studied at the expense of higher hydrocarbon (HC) and carbon monoxide (CO) emissions and an increase in fuel consumption (less than 4%).

This paper describes the simultaneous reduction of nitrogen oxides (NOx) and particulate matter (PM) in a modern light-duty diesel engine under high exhaust gas recirculation (EGR) levels. Simultaneous reduction of NOx and PM emissions was observed under lean conditions at several low to moderate load conditions using two different approaches. The first approach utilizes a throttle to increase EGR rate beyond the maximum rate possible with sole use of the EGR valve for a particular engine condition. The second approach does not use a throttle, but rather uses a combination of EGR and manipulation of injection parameters. A significant reduction in particulate matter size and concentration was observed corresponding to the reduction in particulate mass. This PM reduction was accompanied by a significant shift in the heat release profile. In addition, there were significant cylinder-to-cylinder variations in particulate matter characteristics, gaseous emissions, and heat release.

We present simulated fuel economy and emissions of city transit buses powered by conventional diesel engines and diesel-hybrid electric powertrains of varying size. Six representative city drive cycles were included in the study. In addition, we included previously published aftertreatment device models for control of CO, HC, NOx, and particulate matter (PM) emissions. Our results reveal that bus hybridization can significantly enhance fuel economy by reducing engine idling time, reducing demands for accessory loads, exploiting regenerative braking, and shifting engine operation to speeds and loads with higher fuel efficiency. Increased hybridization also tends to monotonically reduce engine-out emissions, but tailpipe (post-aftertreatment) emissions are affected by complex interactions between engine load and the transient catalyst temperatures, and the emissions results were found to depend significantly on motor size and details of each drive cycle.

We compare the simulated fuel economy and emissions for both conventional and hybrid class 8 heavy-duty diesel trucks operating over multiple urban and highway driving cycles. Both light and heavy freight loads were considered, and all simulations included full aftertreatment for NOx and particulate emissions controls. The aftertreatment components included a diesel oxidation catalyst (DOC), urea-selective catalytic NOx reduction (SCR), and a catalyzed diesel particulate filter (DPF). Our simulated hybrid powertrain was configured with a pre-transmission parallel drive, with a single electric motor between the clutch and gearbox. A conventional heavy duty (HD) truck with equivalent diesel engine and aftertreatment was also simulated for comparison. Our results indicate that hybridization can significantly increase HD fuel economy and improve emissions control in city driving. However, there is less potential benefit for HD hybrid vehicles during highway driving.

NOx emissions from a heavy-duty diesel engine were reduced by more than 90% and 80% utilizing a full-scale ethanol-SCR system for space velocities of 21000/h and 57000/h respectively. These results were achieved for catalyst temperatures between 360 and 400°C and for C1:NOx ratios of 4-6. The SCR process appears to rapidly convert ethanol to acetaldehyde, which subsequently slipped past the catalyst at appreciable levels at a space velocity of 57000/h. Ammonia and N2O were produced during conversion; the concentrations of each were higher for the low space velocity condition. However, the concentration of N2O did not exceed 10 ppm. In contrast to other catalyst technologies, NOx reduction appeared to be enhanced by initial catalyst aging, with the presumed mechanism being sulfate accumulation within the catalyst. A concept for utilizing ethanol (distilled from an E-diesel fuel) as the SCR reductant was demonstrated.

Mixing controlled compression ignition, i.e., diesel engines are efficient and are likely to continue to be the primary means for movement of goods for many years. Low-net-carbon biofuels have the potential to significantly reduce the carbon footprint of diesel combustion and could have advantageous properties for combustion, such as high cetane number and reduced engine-out particle and NOx emissions. We developed a list of over 400 potential biomass-derived diesel blendstocks and populated a database with the properties and characteristics of these materials. Fuel properties were determined by measurement, model prediction, or literature review. Screening criteria were developed to determine if a blendstock met the basic requirements for handling in the diesel distribution system and use as a blend with conventional diesel. Criteria included cetane number ≥40, flashpoint ≥52°C, and boiling point or T90 ≤338°C.

The DOE Office of Heavy Vehicle Technologies (OHVT) and its predecessor organizations have maintained aggressive projects in diesel exhaust aftertreatment since 1993. The Energy Policy Act of 1992, Section 2027, specifically authorized DOE to help accelerate the ability of U. S. diesel engine manufacturers to meet emissions regulations while maintaining the compression ignition engines inherently high efficiency. A variety of concepts and devices have been evaluated for NOx and Particulate matter (PM) control. Additionally, supporting technology in diagnostics for catalysis, PM measurement, and catalyst/reductant systems are being developed. This paper provides a summary of technologies that have been investigated and provides recent results from ongoing DOE-sponsored R&D. NOx control has been explored via active NOx catalysis, several plasma-assisted systems, electrochemical cells, and fuel additives.

Response surface methodology (RSM) techniques were applied to develop a predictive model of electric vehicle (EV) energy consumption over the Environmental Protection Agency's (EPA) standardized drive cycles. The model is based on measurements from a synthetic composite drive cycle. The synthetic drive cycle is a minimized statistical composite of the standardized urban (UDDS), highway (HWFET), and US06 cycles. The composite synthetic drive cycle is 20 minutes in length thereby reducing testing time of the three standard EPA cycles by over 55%. Vehicle speed and acceleration were used as model inputs for a third order least squared regression model predicting vehicle battery power output as a function of the drive cycle. The approach reduced three cycles and 46 minutes of drive time to a single test of 20 minutes.

A minimally invasive spatially resolved capillary inlet mass spectrometer has been used to quantify EGR/air mixing in a Cummins V-8 medium-duty diesel engine. Two EGR-system hardware designs were evaluated in terms of EGR-air mixing at the intake manifold inlet and port-to-port EGR charge uniformity. Performance was assessed at four modalized-FTP engine conditions. One design is found to be considerably better, particularly at three of the four engine conditions. Specific questions such as the effect of maximizing mass air flow on EGR mixing, and if particular cylinders are EGR starved are investigated. The detailed performance characteristics suggest areas to focus improvement efforts, and serve as a foundation for identifying the non-uniformity EGR barriers and origins.

Regulated and unregulated emissions (individual hydrocarbons, ethanol, aldehydes and ketones, polynuclear aromatic hydrocarbons (PAH), nitro-PAH, and soluble organic fraction of particulate matter) were characterized in engines utilizing duplicate ISO 8178-C1 eight-mode tests and FTP smoke tests. Certification No. 2 diesel (400 ppm sulfur) and three ethanol/diesel blends, containing 7.7 percent, 10 percent, and 15 percent ethanol, respectively, were used. The three, Tier II, off-road engines were 6.8-L, 8.1-L, and 12.5-L in displacement and each had differing fuel injection system designs. It was found that smoke and particulate matter emissions decreased with increasing ethanol content. Changes to the emissions of carbon monoxide and oxides of nitrogen varied with engine design, with some increases and some decreases. As expected, increasing ethanol concentration led to higher emissions of acetaldehyde (increases ranging from 27 to 139 percent).

In model year 1983, new car MPG declined for the first time in ten years. Accompanying this decline in MPG, the size of the average car increased, car weights and engine sizes increased and diesel sales declined - all reversing their movements over the previous ten years. Using carline MPG estimates and sales figures, it is estimated that new car MPG declined 0.29 in 1983 after rising 6.70 MPG over the previous four years. Furthermore, it is estimated that actions by new car buyers would have lowered the 1983 MPG 0.40 MPG through the purchase of larger cars, cars with larger engines and fewer diesel engines if the manufacturers had not made some fuel economy improvements and introduced some new high-MPG cars. A simple model of future fuel use increases as a function of MPG levels below a specified level consistent with the CAFE standards shows that the costs of lower fuel economy will only gradually be felt, but that these costs will increase over time and persist for over a decade.

Radio frequency (RF)-based sensors provide a direct measure of the particulate filter loading state. In contrast to particulate matter (PM) sensors, which monitor the concentration of PM in the exhaust gas stream for on-board diagnostics purposes, RF sensors have historically been applied to monitor and control the particulate filter regeneration process. This work developed an RF-based particulate filter control system utilizing both conventional and fast response RF sensors, and evaluated the feasibility of applying fast-response RF sensors to provide a real-time measurement of engine-out PM emissions. Testing with a light-duty diesel engine equipped with fast response RF sensors investigated the potential to utilize the particulate filter itself as an engine-out soot sensor.

A technique for rapid in situ measurement of the fuel dilution of oil in a diesel engine is presented. Fuel dilution can occur when advanced in-cylinder fuel injection techniques are employed for the purpose of producing rich exhaust for lean NOx trap catalyst regeneration. Laser-induced fluorescence (LIF) spectroscopy is used to monitor the oil in a Mercedes 1.7-liter engine operated on a dynamometer platform. A fluorescent dye suitable for use in diesel fuel and oil systems is added to the engine fuel. The LIF spectra are monitored to detect the growth of the dye signal relative to the background oil fluorescence; fuel mass concentration is quantified based on a known sample set. The technique was implemented with fiber optic probes which can be inserted at various points in the engine oil system. A low cost 532-nm laser diode was used for excitation.