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A commercial three-way catalyst (TWC) was evaluated for ammonia (NH3) generation on a 2.0-liter BMW lean burn gasoline direct injection engine as a component in a passive ammonia selective catalytic reduction (SCR) system. The passive NH3 SCR system is a potential low cost approach for controlling nitrogen oxides (NOX) emissions from lean burn gasoline engines. In this system, NH3 is generated over a close-coupled TWC during periodic slightly rich engine operation and subsequently stored on an underfloor SCR catalyst. Upon switching to lean, NOX passes through the TWC and is reduced by the stored NH3 on the SCR catalyst. NH3 generation was evaluated at different air-fuel equivalence ratios at multiple engine speed and load conditions. Near complete conversion of NOX to NH3 was achieved at λ=0.96 for nearly all conditions studied. At the λ=0.96 condition, HC emissions were relatively minimal, but CO emissions were significant.

Lean gasoline engines offer greater fuel economy than the common stoichiometric gasoline engine, but the current three way catalyst (TWC) on stoichiometric engines is unable to control nitrogen oxide (NOX) emissions in oxidizing exhaust. For these lean gasoline engines, lean NOX emission control is required to meet existing Tier 2 and upcoming Tier 3 emission regulations set by the U.S. Environmental Protection Agency (EPA). While urea-based selective catalytic reduction (SCR) has proven effective in controlling NOX from diesel engines, the urea storage and delivery components can add significant size and cost. As such, onboard NH3 production via a passive SCR approach is of interest. In a passive SCR system, NH3 is generated over a close-coupled TWC during periodic slightly rich engine operation and subsequently stored on an underfloor SCR catalyst. Upon switching to lean operation, NOX passes through the TWC and is reduced by the stored NH3 on the SCR catalyst.

The combination of advanced combustion with advanced selective catalytic reduction (SCR) catalyst formulations was studied in the work presented here to determine the impact of the unique hydrocarbon (HC) emissions from premixed charge compression ignition (PCCI) combustion on SCR performance. Catalyst core samples cut from full size commercial Fe- and Cu-zeolite SCR catalysts were exposed to a slipstream of raw engine exhaust from a 1.9-liter 4-cylinder diesel engine operating in conventional and PCCI combustion modes. The zeolites which form the basis of these catalysts are different with the Cu-based catalyst made on a chabazite zeolite which has smaller pore structures relative to the Fe-based catalyst. Subsequent to exposure, bench flow reactor characterization of performance and hydrocarbon release and oxidation enabled evaluation of overall impacts from the engine exhaust.

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.

Ethanol is a biofuel commonly used in gasoline blends to displace petroleum consumption; its utilization is on the rise in the United States, spurred by the biofuel utilization mandates put in place by the Energy Independence and Security Act of 2007 (EISA). The United States Environmental Protection Agency (EPA) has the statutory responsibility to implement the EISA mandates through the promulgation of the Renewable Fuel Standard. EPA has historically mandated an emissions certification fuel specification that calls for ethanol-free fuel, except for the certification of flex-fuel vehicles. However, since the U.S. gasoline marketplace is now virtually saturated with E10, some organizations have suggested that inclusion of ethanol in emissions certification fuels would be appropriate.

The Energy Independence and Security Act of 2007 requires the U.S. to use 36 billion gallons of renewable fuel per year by 2022. Domestic ethanol production has increased steadily in recent years, growing from less than 5 billion gallons per year (bgpy) in 2006 to over 13 bgpy in 2010. While there is interest in developing non-oxygenated renewable fuels for use in conventional vehicles as well as interest in expanding flex-fuel vehicle (FFV) production for increased E85 use, there remains concern that EISA compliance will require further use of oxygenated biofuels in conventional vehicles. The Environmental Protection Agency (EPA) recently granted partial approval to a waiver allowing the use of E15 in 2001 and newer light-duty vehicles.

During the 1980s, the U.S. Environmental Protection Agency (EPA) incorporated the R factor into fuel economy calculations in order to address concerns about the impacts of test fuel property variations on corporate average fuel economy (CAFE) compliance, which is determined using the Federal Test Procedure (FTP) and Highway Fuel Economy Test (HFET) cycles. The R factor is defined as the ratio of the percent change in fuel economy to the percent change in volumetric heating value for tests conducted using two differing fuels. At the time the R-factor was devised, tests using representative vehicles initially indicated that an appropriate value for the R factor was 0.6. Reassessing the R factor has recently come under renewed interest after EPA's March 2013 proposal to adjust the properties of certification gasoline to contain significant amounts of ethanol.

Ethanol is a very attractive fuel from an end-use perspective because it has a high chemical octane number and a high latent heat of vaporization. When an engine is optimized to take advantage of these fuel properties, both efficiency and power can be increased through higher compression ratio, direct fuel injection, higher levels of boost, and a reduced need for enrichment to mitigate knock or protect the engine and aftertreatment system from overheating. The ASTM D5798 specification for high level ethanol blends, commonly called “E85,” underwent a major revision in 2011. The minimum ethanol content was revised downward from 68 vol% to 51 vol%, which combined with the use of low octane blending streams such as natural gasoline introduces the possibility of a lower octane “E85” fuel.

Saab Automobile recently released the BioPower engines, advertised to use increased turbocharger boost and spark advance on ethanol fuel to enhance performance. Specifications for the 2.0 liter turbocharged engine in the Saab 9-5 Biopower 2.0t report 150 hp (112 kW) on gasoline and a 20% increase to 180 hp (134 kW) on E85 (nominally 85% ethanol, 15% gasoline). While FFVs sold in the U.S. must be emissions certified on Federal Certification Gasoline as well as on E85, the European regulations only require certification on gasoline. Owing to renewed and growing interest in increased ethanol utilization in the U.S., a European-specification 2007 Saab 9-5 Biopower 2.0t was acquired by the Department of Energy and Oak Ridge National Laboratory (ORNL) for benchmark evaluations. Results show that the vehicle's gasoline equivalent fuel economy on the Federal Test Procedure (FTP) and the Highway Fuel Economy Test (HFET) are on par with similar U.S.-legal flex-fuel vehicles.

A prototype emissions control system consisting of a close-coupled lightoff catalyst, catalyzed diesel particle filter (CDPF), and a NOX adsorber was evaluated on a Mercedes A170 CDI. This laboratory experiment aimed to determine whether the benefits of these technologies could be utilized simultaneously to allow a light-duty diesel vehicle to achieve levels called out by U.S. Tier 2 emissions legislation. This research was carried out by driving the A170 through the U.S. Federal Test Procedure (FTP), US06, and highway fuel economy test (HFET) dynamometer driving schedules. The vehicle was fueled with a 3-ppm ultra-low sulfur fuel. Regeneration of the NOX adsorber/CDPF system was accomplished by using a laboratory in-pipe synthesis gas injection system to simulate the capabilities of advanced engine controls to produce suitable exhaust conditions. The results show that these technologies can be combined to provide high pollutant reduction efficiencies in excess of 90% for NOX and PM.

A 1999 Mercedes A170 CDI has been equipped with prototype NOX adsorber devices in order to study the impacts of regeneration conditions on the emissions reduction performance of the devices. This study consisted of a number of laboratory experiments utilizing a bottled-gas injection system to periodically provide fuel-rich exhaust conditions for device regeneration. The NOX adsorbers were evaluated on the LA4 driving cycle using a fixed regeneration schedule. The rich-pulse duration and minimum air/fuel ratio during the rich pulse were varied and the impacts upon pollutant emission rates measured. Results are presented for 5 prototype NOX adsorbers.

NOx reduction product speciation during regeneration of a fully formulated lean NOx trap catalyst has been investigated using a bench-scale flow reactor. NH3 and N2O were both observed during the regeneration phase of fast lean/rich cycles that simulated engine operation. Formation of both products increased with higher reductant concentrations and lower temperatures. Steady flow experiments were used to decouple the regeneration reactions from the NOx storage and release processes. This approach enabled a detailed investigation into the reactions that cause both formation and destruction of non-N2 reduction products. Pseudo-steady state experiments with simultaneous flow of NOx and reductant indicated that high concentrations of CO or H2 drive the reduction reactions toward NH3 formation, while mixtures that are stoichiometric for N2 formation favor N2. These experiments also showed that NH3 is readily oxidized by both NO and O2 over the LNT catalyst.

Laser-induced incandescence is used to measure time-resolved diesel particulate emissions for two lean NOx trap regeneration strategies that utilize intake throttling and in-cylinder fuel enrichment. The results show that when the main injection event is increased in duration and delayed 13 crank-angle degrees, particulate emissions are very high. For a repetitive pattern of 3 seconds of rich regeneration followed by 27 seconds of NOx-trap loading, we find a monotonic increase in particulate emissions during the loading intervals that approaches twice the initial baseline particulate level after 1000 seconds. In contrast, particulate emissions during the regeneration intervals are constant throughout the test sequence.

Compression and leak-down tests are frequently used to identify and diagnose failed engine power cylinders. It is also often desirable in research and testing programs to use these tests to monitor incremental changes in cylinder leakage. This paper investigates whether these tests are adequate in their present form to monitor incremental changes in cylinder leakage. Results are presented from two vehicle fleets at two test sites. Compression and leak-down tests were conducted on these fleets periodically during a mileage accumulation study. The results were used to establish the variability inherent in the compression and leak-down test processes. Comparisons between the results at the initial mileage test for the study vehicles with those at the final mileage test are shown to be largely within the uncertainty established for repeat assessments.

Ethanol is a very effective reductant for nitrogen oxides (NOX) over silver/alumina (Ag/Al2O3) catalysts in lean exhaust environments. With the widespread availability of ethanol/gasoline-blended fuel in the U.S., lean gasoline engines equipped with Ag/Al2O3 catalysts have the potential to deliver higher fuel economy than stoichiometric gasoline engines and to increase biofuel utilization while meeting exhaust emissions regulations. In this work a pre-commercial 2 wt% Ag/Al2O3 catalyst was evaluated on a 2.0-liter BMW lean burn gasoline direct injection engine for the selective catalytic reduction (SCR) of NOX with ethanol/gasoline blends. The ethanol/gasoline blends were delivered via in-pipe injection upstream of the Ag/Al2O3 catalyst with the engine operating under lean conditions. A number of engine conditions were chosen to provide a range of temperatures and space velocities for evaluation of catalyst performance.

The compatibility of key fuel system infrastructure elastomers with promising bio-blendstock fuel candidates was examined using Hansen solubility analysis. Thirty-four candidate fuels were evaluated in this study including multiple alcohols, esters, ethers, ketones, alkenes and one alkane. These compounds were evaluated as neat molecules and as blends with the gasoline surrogate, dodecane and a mix of dodecane and 10% ethanol (E10D). The elastomer materials were fluorocarbon, acrylonitrile butadiene rubber (NBR), styrene butadiene (SBR), neoprene, polyurethane and silicone. These materials have been rigorously studied with other fuel types, and their measured volume change results were found to correspond well with their predicted solubility levels. The alcohols showed probable compatibility with fluorocarbon and polyurethane, but are not likely to be compatible at low blend levels with NBR and SBR.