Richard Hugh Clark

Effects of GTL Fuel Properties on DI Diesel Combustion

Reduction of vehicle exhaust emissions is an important contributor to improved air quality. At the same time demand is growing for new transportation fuels that can enhance security and diversity of energy supply. Gas to Liquids (GTL) Fuel has generated much interest from governments and automotive manufacturers. It is a liquid fuel derived from natural gas, and its properties - sulphur free, low polyaromatics and high cetane number - make it desirable for future clean light-duty diesel engines. In this paper, the effects of distillation characteristics and cetane number of experimental GTL test fuels on direct injection (Dl) diesel combustion and exhaust emissions were investigated, together with their spray behaviour and mixing characteristics. The test results show that the lower distillation test fuels produce the largest reductions in smoke and PM emissions even at high cetane numbers. This is linked to the enhanced air/fuel mixing of the lighter fuel in a shorter time. The high ignitability and short ignition delay resulting from the high cetane number of all the GTL samples proved effective for reduction of unburnt emissions and combustion noise. Some experimental results are also presented when a modern high speed Dl diesel passenger car is run on neat GTL fuel and conventional diesel fuel. As the test results show, some benefits of GTL have been confirmed in exhaust emissions.

Fuel Property, Emission Test, and Operability Results from a Fleet of Class 6 Vehicles Operating on Gas-to-Liquid Fuel and Catalyzed Diesel Particle Filters

A fleet of six 2001 International Class 6 trucks operating in southern California was selected for an operability and emissions study using gas-to-liquid (GTL) fuel and catalyzed diesel particle filters (CDPF). Three vehicles were fueled with CARB specification diesel fuel and no emission control devices (current technology), and three vehicles were fueled with GTL fuel and retrofit with Johnson Mattheys CCRT diesel particulate filter. No engine modifications were made.

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.

An Investigation of the Physical and Chemical Factors Affecting the Performance of Fuels in the JFTOT

Earlier research performed by Shell Research sought to compare the performance of fuels in the Jet Fuel Thermal Oxidation Tester (JFTOT) with that in a simulated engine oil cooler. However the agreement between the rigs was poor and initial attempts to improve the correlation by modifying various JFTOT operating parameters were ineffective. Now, those same operating parameters have been readdressed in more detail, in order to determine the physical and chemical factors which control fuel response in the JFTOT

Dedicated GTL Vehicle: A Calibration Optimization Study

GTL (Gas-To-Liquid) fuel is well known to improve tailpipe emissions when fuelling a conventional diesel vehicle, that is, one optimized to conventional fuel. This investigation assesses the additional potential for GTL fuel in a GTL dedicated vehicle. This potential for GTL fuel was quantified in an EU 4 6-cylinder serial production engine. In the first stage, a comparison of engine performance was made of GTL fuel against conventional diesel, using identical engine calibrations. Next, adaptations enabled the full potential of GTL fuel within a dedicated calibration to be assessed. For this stage, two optimization goals were investigated: • Minimization of NOx emissions • Minimization of fuel consumption

Future fuels and lubricant base oils from Shell Gas to Liquids (GTL) technology

Shell was the first oil marketer to bring to commercial scale, Gas to Liquids (GTL) technology for fuels and base oils production. This started with the commissioning of the multi-purpose GTL facility at Bintulu, Malaysia in 1993. The plant produces both automotive gas oil (GTL Fuel) as well as a number of speciality products including detergent feedstocks, a range of Fisher-Tropsch commercial wax grades, and a feedstock for base oils production. The base oil feedstock has been shipped to Shell facilities in Japan and France since 1994 where it is solvent de-waxed to produce the first commercially available GTL base oils. The GTL Fuel is currently being used in premium diesels in Germany, Greece and Thailand. Shell has announced in 2003 its intention to build two world scale GTL trains in Qatar and this will include substantial fuels and base oils facilities. The diesel cut is characterised by very good cetane quality, low density, plus negligible sulphur and aromatics contents; such properties make it potentially valuable as a fuel with lower emissions than conventional automotive gas oil, either as a standalone fuel or in blends. The base oils will cover a wide grade range with the majority of volume being API Group III grades of 4 cSt and above. These base oil grades will show the superior additive responses expected from 100% saturates catalytically de-waxed base oils.

Impact of FAME Content on the Regeneration Frequency of Diesel Particulate Filters (DPFs)

Modern diesel vehicles utilize two technologies that have been motivated by recent European legislation: diesel fuel blends containing Fatty Acid Methyl Esters (FAME) and Diesel Particulate Filters (DPF). Oxygenates, like FAME, are known to reduce PM formation in the combustion chamber and reduce the amount of soot that must be filtered from the engine exhaust by the DPF. This effect is also expected to lengthen the time between DPF regenerations and reduce the fuel consumption penalty that is associated with soot loading and regeneration. This study investigated the effect of FAME content, up to 50% v/v (B50), in diesel fuel on the DPF regeneration frequency by repeatably running a Euro 5 multi-cylinder bench engine over the NEDC until a specified soot loading limit had been reached. The results verify the expected reduction of engine-out PM emissions with increasing FAME content and the reduction in fuel consumption penalty associated with reducing the frequency of DPF regenerations.