Richard Stradling

The Lubricity of Deeply Hydrogenated Diesel Fuels - The Swedish Experience

Environmentally adapted diesel fuels defined by the Swedish Government contain extremely low levels of sulphur and have limited aromatics contents. Road trials and pump durability tests of these fuels revealed unacceptable wear in injection pumps due to low lubricity. Additive solutions were identified using bench tests and then proven in field trials. Market experience has substantiated the findings that fuels using the chosen additive give fully satisfactory performance. This paper illustrates how practical solutions to lubricity questions can be found, and is applicable wherever specifications demand fuels requiring a high degree of hydroprocessing. 19 refs., 10 figs., 3 tabs.

Fuel quality effects on particulate matter emissions from light-and heavy-duty diesel engines

This paper gives an update of Shell`s ongoing research on correlations between diesel fuel quality and particulate emissions in both heavy and light duty applications. An exhaust oxidation catalyst selectively decreases the particulate hydrocarbon fraction, leaving the fixed carbon fraction unaffected. This overall particulates reduction mechanism explains why particulate emissions from catalyst vehicles are less sensitive towards changes in fuel quality. An attempt has been made to explain the differences observed between particulate emissions from heavy- and light-duty engines. It is tentatively concluded that differences originate mainly from intrinsic differences between the heavy- and light-duty test cycles. 27 refs., 14 figs., 5 tabs.

Fuel effects on regulated emissions from modern gasoline vehicles

\ 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 CO 2 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.

Fuel Effects on Regulated Emissions From Advanced Diesel Engines and Vehicles

The introduction of sulphur-free fuels will enable advanced engine and exha st after-treatment technologies to meet increasingly stringent exhaust emissions regulations. As these cleaner fuels and vehicles are introduced, the potential for further improvements in air quality through changes to fuel properties can be expected to diminish. Nevertheless, CONCAWE has continued to update knowledge by evaluating fuel effects on emissions from new engine/vehicle technologies as they approach the market. In this work, carried out as part of CONCAWEs contribution to the EU PARTICULATES consortium [1], two advanced light-duty diesel vehicles and three heavy-duty diesel engines covering Euro-3 to Euro-5 technologies, were tested. The fuels tested covered a range of sulphur content and compared conventional fuels with extreme fuel compositions such as Swedish Class 1 and Fischer Tropsch diesel fuels. The emissions benefits from the advanced engine/vehicle technologies operating on sulphur-free fuels are impressive and likely to bring substantial improvements in European air quality as the vehicle fleet is replaced. Particulate filters have the potential to reduce diesel particulate mass (PM) emissions by more than an order of magnitude. Capability for substantial improvements in control of NOx emissions is also evident. Fuel effects on PM and NOx emissions were also observed. In Euro-3 engines, the effects from extreme fuel changes were in the range of 10-20%. When advanced emission control technologies such as diesel particulate filters (DPFs) were used, PM emissions were so low that the impact of changing fuel properties became negligible. Extreme fuel changes continued to affect NOx emissions even with the advanced engine technologies, although these fuels also reduced maximum power. Optimisation of the exhaust after-treatment was also important, with increasing urea rate reducing NOx emissions. Further progress on NOx emissions can be expected as control of engine-out emissions improves and NOx after-treatment technology matures, with the availability of sulphur-free fuels.

Statistical design and analysis of a test programme to assess the volatility characteristics of ethanol/gasoline blends

Designing a measurement programme to assess the volatility characteristics of ethanol/gasoline blends posed challenges as the seven base fuel properties of interest were highly constrained and difficult to manipulate independently of one another. The target base fuel matrix was generated by augmenting a 49-fuel fraction of a 75 factorial with 11 additional fuels chosen using D-optimality. Two of the five factors were treated as pseudo-factors and used to generate the levels of two pairs of mutually constrained properties. The 60 base fuels were then blended and subsequently splash blended with 5%, 10%, 15%, 20% & 25% ethanol. The test order for the resulting 360 fuels was structured and randomized to reduce the risk of extraneous sources of variation contaminating the regression models subsequently fitted to the data. Cross-concentration models had to be fitted by generalized least squares techniques as the measured values of the principal dependent variable were structurally correlated.