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Certain diesel fuel specification properties are considered to be environmental parameters according to the European Fuels Quality Directive (FQD, 2009/EC/30) and previous regulations. These limits included in the EN 590 specification were derived from the European Programme on Emissions, Fuels and Engine Technologies (EPEFE) which was carried out in the 1990’s on diesel vehicles meeting Euro 2 emissions standards. These limits could potentially constrain FAME blending levels higher than 7% v/v. In addition, no significant work has been conducted since to investigate whether relaxing these limits would give rise to performance or emissions debits or fuel consumption benefits in more modern vehicles. The objective of this test programme was to evaluate the impact of specific diesel properties on emissions and fuel consumption in Euro 4, Euro 5 and Euro 6 light-duty diesel vehicle technologies.

The performance aspect of gasoline combustion has traditionally been measured using Research Octane Number (RON) and Motor Octane Number (MON) which describe antiknock performance under different conditions. Recent literature suggests that MON is less important than RON in modern cars and a relaxation in the MON specification could improve vehicle performance, while also helping refiners in the production of gasoline. At the same time, for the same octane number change, increasing RON appears to provide more benefit to engine power and acceleration than reducing MON. It has also been suggested that there could be fuel efficiency benefits (on a tank to wheels basis) for specially adapted engines, for example, operating at higher compression ratio, on very high RON (100+). Other workers have advocated the use of an octane index (OI) which incorporates both RON and MON to give an indication of octane quality.

A broad range of diesel, kerosene, and gasoline-like fuels has been tested in a single-cylinder diesel engine optimized for advanced combustion performance. These fuels were selected in order to better understand the effects of ignition quality, volatility, and molecular composition on engine-out emissions, performance, and noise levels. Low-level biofuel blends, both biodiesel (FAME) and ethanol, were included in the fuel set in order to test for short-term advantages or disadvantages. The diesel engine optimized in Part 1 of this study included cumulative engine hardware enhancements that are likely to be used to meet Euro 6 emissions limits and beyond, in part by operating under conditions of Homogeneous Charge Compression Ignition (HCCI), at least over some portions of the speed and load map.

Two single-cylinder diesel engines were optimised for advanced combustion performance by means of practical and cumulative hardware enhancements that are likely to be used to meet Euro 5 and 6 emissions limits and beyond. These enhancements included high fuel injection pressures, high EGR levels and charge cooling, increased swirl, and a fixed combustion phasing, providing low engine-out emissions of NOx and PM with engine efficiencies equivalent to today's diesel engines. These combustion conditions approach those of Homogeneous Charge Compression Ignition (HCCI), especially at the lower part-load operating points. Four fuels exhibiting a range of ignition quality, volatility, and aromatics contents were used to evaluate the performance of these hardware enhancements on engine-out emissions, performance, and noise levels.

Recent years have seen dramatic reductions in gasoline and diesel sulfur concentrations in the United States, Europe, Japan and other countries. Many developing countries are evaluating the appropriate sulfur levels to choose for the future. This paper examines the current state of knowledge concerning the impact of fuel sulfur on exhaust emissions, and the sensitivity of exhaust aftertreatment technology to fuel sulfur. Gasoline vehicles achieve very low emissions through use of three-way catalysts. These systems are relatively insensitive to sulfur, being able to operate on levels of up to 500 ppm. Further reduction in sulfur will produce additional, small emission reductions. Diesel emissions may be reduced significantly using engine modifications, oxidation catalysts or exhaust gas recirculation, which may require sulfur levels of 500 ppm.

A consortium of CONCAWE, EUCAR and the EU Commission's JRC carried out a Well-to-Wheels analysis of a wide range of automotive fuels and powertrains. The study gives an assessment of the energy consumption and greenhouse gas emissions for each pathway. It also considers macroeconomic costs and the market potential of alternative fuels.

The influence of gasoline quality on exhaust emissions has been evaluated using four modern European gasoline cars with advanced features designed to improve fuel economy and CO2 emissions, including stoichiometric direct injection, lean direct injection and MPI with variable valve actuation. Fuel effects studied included sulphur content, evaluated over a range from 4 to 148 mg/kg, and other gasoline properties, including aromatics content, olefins content, volatility and final boiling point (FBP). All four cars achieved very low emissions levels, with some clear differences between the vehicle technologies. Even at these low emissions levels, all four cars showed very little short-term sensitivity to gasoline sulphur content. The measured effects of the other gasoline properties were small and often conflicting, with differing directional responses for different vehicles and emissions.

This paper summarizes a program to investigate the impact of a variety of oxygenates on diesel exhaust emissions, especially particulate matter (PM) and NOx emissions. Oxygenates have been studied at great length already and have been shown to be an effective method for reducing particulate emissions, although high cost remains a barrier to their widespread use. Our objectives were to assess whether some oxygenates could be more effective than others and why. Fourteen different oxygenates were studied. Testing was carried out primarily in a single cylinder heavy duty Caterpillar engine under high and low load conditions. Complementary testing was performed in three vehicles spanning a range of vehicle technologies. Most of the testing used a single base fuel which served as the reference fuel although some tests were also done using a newly produced ultra low sulfur automotive diesel oil (ULSADO). Larger particulate matter reductions were found at high load than at low load.

Air quality monitoring of PM10 and associated health studies have focused interest on the size and the number of particles emitted to, and found in, the atmosphere. Automotive sources are one of the important elements in this, and CONCAWE have completed a study of heavy duty diesel particle emissions, complementing their previously reported light duty work. This heavy duty programme, presented here, investigated the nature of particulate emissions from two heavy duty engines (representative of different emissions levels), operating on three marketed fuels, over their respective European legislative heavy duty test cycles. The programme has investigated some of the complexities associated with obtaining credible data (e.g. dilution ratios, system stabilisation time etc.). The number distributions, which were measured over a wide size range (3 to 1000 nm), have been split into two size ranges, representative of nucleation mode and accumulation mode particles.