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With ongoing concerns about the elevated levels of ambient air pollution in urban areas and the contribution from heavy-duty diesel vehicles, hybrid electric vehicles are considered as a potential solution as they are perceived to be more fuel efficient and less polluting than their conventional engine counterparts. However, recent studies have shown that real-world emissions may be substantially higher than those measured in the laboratory, mainly due to operating conditions that are not fully accounted for in dynamometer test cycles. At the U.S. EPA National Fuel and Vehicle Emissions Laboratory (NVFEL) the in-use criteria emissions and energy efficiency of heavy-duty class 8 vehicles (up to 36280 kg) can be evaluated under controlled conditions in the heavy-duty chassis dynamometer test.

Dimethyl Ether (DME) is a promising future compression ignition fuel, particularly when derived from renewable, CO2-neutral feedstocks. While it is generally well-known that DME produces very little soot when burned, few studies have explored its low-temperature combustion behavior, where the potential for ultra-low engine-out emissions of both NOx and soot may exist. The present work shows the results of a single-cylinder engine operating with DME below the level of the US 2010 Heavy Duty Onroad Standard for NOx, without NOx aftertreatment. A high-pressure oil-over-fuel intensified injection system was used to maintain proper air utilization and high combustion efficiency, in combination with intake oxygen control using relatively high levels of EGR for low NOx. Fuel-related material issues notwithstanding, the engine results point toward a potentially cost-effective and efficient means of utilizing bio-derived fuels.

Alcohols hold promise as future spark ignition fuels, particularly when produced from renewable, CO2-neutral feedstocks. Among the more environmentally and economically attractive renewable-source fuels are ethanol and methanol derived from cellulosic or woody biomass materials. When used with engines optimized for alcohol fuels, the life-cycle carbon imprint of these bio-derived fuels sets the benchmark for comparing all other transportation prime movers and their fuels. The present work examines the performance of high-level ethanol and methanol fuel blends with gasoline in a turbocharged, port-fuel-injected, high compression ratio medium duty engine. The results clearly point a way to cost-effective, highly efficient means of utilizing bio-derived spark ignition fuels.

With increasingly stringent light duty particulate emissions regulations, it is of great interest to better understand particulate matter formation. Helping to build the knowledge base for a thorough understanding of particulate matter formation will be an essential step in developing effective control strategies. It is especially important to do this in such a way as to emulate real driving behaviors, including cold starts and transients. To this end, this study examined particulate emissions during transient operation in a recent model year vehicle equipped with a GDI engine. Three of the major federal test cycles were selected as evaluation schemes: the FTP, the HWFET, and the US06. These cycles capture much of the driving behaviors likely to be observed in typical driving scenarios. Measurements included particle size distributions from a TSI EEPS fast-response particle spectrometer, as well as real-time soot emissions from an AVL MSS soot sensor.

The U.S. Environmental Protection Agency, U.S. Department of Transportation's National Highway and Traffic Safety Administration, and the California Air Resources Board have recently released proposed new regulations for greenhouse gas emissions and fuel economy for light-duty vehicles and trucks in model years 2017-2025. These proposed regulations intend to significantly reduce greenhouse gas emissions and increase fleet fuel economy from current levels. At the fleet level, these rules the proposed regulations represent a 50% reduction in greenhouse gas emissions by new vehicles in 2025 compared to current fleet levels. At the same time, global growth, especially in developing economies, should continue to drive demand for crude oil and may lead to further fuel price increases. Both of these trends will therefore require light duty vehicles (LDV) to significantly improve their greenhouse gas emissions over the next 5-15 years to meet regulatory requirements and customer demand.