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Rose K.D.,CONCAWE | Samaras Z.,Aristotle University of Thessaloniki | Clark R.,Royal Dutch Shell | Elliott N.,Esso Petroleum Co. | And 6 more authors.
SAE International Journal of Fuels and Lubricants

Fatty Acid Methyl Ester (FAME) products derived from vegetable oils and animal fats are now widely used in European diesel fuels and their use will increase in order to meet mandated targets for the use of renewable products in road fuels. As more FAME enters the diesel pool, understanding the impact of higher FAME levels on the performance and emissions of modern light-duty diesel vehicles is increasingly important. Of special significance to Well-to-Wheels (WTW) calculations is the potential impact that higher FAME levels may have on the vehicle's volumetric fuel consumption. The primary objective of this study was to generate statistically robust fuel consumption data on three light-duty diesel vehicles complying with Euro 4 emissions regulations. These vehicles were evaluated on a chassis dynamometer using four fuels: A hydrocarbon-only diesel fuel and three FAME/diesel fuel blends containing up to 50% v/v FAME. One FAME type, a Rapeseed Methyl Ester (RME), was used throughout. One vehicle was equipped only with an oxidation catalyst while the other two were also equipped with two types of Diesel Particulate Filters (DPFs). In addition to CO 2 emissions, regulated tailpipe emissions (NOx, HC, CO, PM, and PN) were collected in order to evaluate the impact of higher RME contents on emissions performance. The results obtained over the New European Driving Cycle (NEDC) indicate that the volumetric fuel consumption systematically increases with increasing RME content for all three vehicles. Within the statistical precision, the vehicles were not able to compensate for the lower energy content of the RME/diesel blends and consumed more fuel in direct proportion to the lower energy content of the RME/diesel blends. As the RME content of the fuel increased, the particulate mass (PM) and solid particle number (PN) were generally found to decrease over the NEDC while the NOx, CO, and HC emissions increased. The overall impact of RME on regulated tailpipe emissions is much smaller, however, compared to the variations in emissions seen over the NEDC sub-cycles. © 2010 SAE International. Source

Crua C.,University of Brighton | Shoba T.,University of Brighton | Heikal M.,University of Brighton | Gold M.,BP Global Fuels Technology | Higham C.,BP Global Fuels Technology
SAE Technical Papers

The formation and breakup of diesel sprays was investigated experimentally on a common rail diesel injector using a long range microscope. The objectives were to further the fundamental understanding of the processes involved in the initial stage of diesel spray formation. Tests were conducted at atmospheric conditions and on a rapid compression machine with motored in-cylinder peak pressures up to 8 MPa, and injection pressures up to 160 MPa. The light source and long range imaging optics were optimised to produce blur-free shadowgraphic images of sprays with a resolution of 0.6 μm per pixel, and a viewing region of 768× 614 μm. Such fine spatial and temporal resolutions allowed the observation of previously unreported shearing instabilities and stagnation point on the tip of diesel jets. The tip of the fuel jet was seen to take the shape of an oblate spheroidal cap immediately after leaving the nozzle, due to the combination of transverse expansion of the jet and the physical properties of the fuel. The spheroidal cap was found to consist of residual fuel trapped in the injector hole after the end of the injection process. The formation of fuel ligaments close to the orifice was also observed, ligaments which were subsequently seen to breakup into droplets through hydrodynamic and capillary instabilities. An ultra-high speed camera was then used to capture the dynamics of the early spray formation and primary breakup with fine temporal and spatial resolutions. The frame rate was up to 5 million images per second and exposure time down to 20 ns, with a fixed resolution of 1280× 960 pixels covering a viewing region of 995× 746 μm. A vortex ring motion within the vapourised spheroidal cap was identified, and resulted in a slipstream effect which led to a central ligament being propelled ahead of the liquid jet. Copyright © 2010 SAE International. Source

Hellier P.,University College London | Ladommatos N.,University College London | Allan R.,BP Global Fuels Technology | Payne M.,BP Global Fuels Technology | Rogerson J.,BP Global Fuels Technology
SAE International Journal of Fuels and Lubricants

Diesel fuels usually comprise a wide range of compounds having different molecular structures which can affect both the fuel's physical properties and combustion characteristics. In future, as synthetic fuels from fossil and sustainable sources become increasingly available, it could be possible to control the fuel's molecular structure to achieve clean and efficient combustion. This paper presents experimental results of combustion and emissions studies undertaken on a single cylinder diesel engine supplied with 18 different fuels each comprising a single, acyclic, non-oxygenated hydrocarbon molecule. These molecules were chosen to highlight the effect of straight carbon chain length, degree of saturation and the addition of methyl groups as branches to a straight carbon chain. The engine tests were carried out at constant injection timing and they were repeated at constant ignition timing and at constant ignition delay, the latter being achieved through the addition to the various fuels of small quantities of ignition improver (2-ethylhexyl nitrate). In tests conducted at constant injection and constant ignition timing the ignition delay of the molecule was found to be the primary driver of combustion phasing, the balance between premixed and diffusion-controlled combustion and, thereby, exhaust emissions. However, the elimination of ignition delay as a variable, using ignition improver, revealed further, subtler, secondary combustion effects also attributable to the molecular structure of the fuels tested. For example, with constant ignition delay, the premixed burn fraction and oxides of nitrogen in the exhaust for the various fuels correlated well with the volatility and the adiabatic flame temperature. © 2011 Society of Automotive Engineers of Japan, Inc. and SAE International. Source

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