ОңТҮстік қазақстан медицина академиясы, хабаршы №4 942, 2021 жыл, том 2
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- Compression Ignition Engines
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ОҢТҮСТІК ҚАЗАҚСТАН МЕДИЦИНА АКАДЕМИЯСЫ, ХАБАРШЫ №4(942, 2021 жыл, ТОМ 2 118 Dedicated ethanol vehicles are even more efficient in using pure ethanol due to better combustion characteristics than FFVs which must retain dual-fuel capability. In these engines the compression ratio is increased. According to WWI (2006), the average fuel consumption has been 25 % lower than for equivalent E20/E25 fueled versions. Most experience with this technology is made in Brazil, again. Volkswagen, Fiat, General Motors, and Ford have all produced dedicated ethanol versions for more than 25 years, with full warranty coverage. Compression Ignition Engines Compression ignition engines, also called diesel engines, are internal combustion engines in which the fuel is ignited by high pressure and temperature, rather than by a separate source of ignition, such as a spark plug, as is the case in the spark ignition engine. The German pioneer Rudolf Diesel invented this type of engine in 1892. He also demonstrated that this engine is running with peanut oil, too. Originally, compression ignition engines are designed for being fuelled with diesel. Nevertheless also ethanol can be combusted in these engines, but this application is limited. For example, since ethanol is difficult to ignite in a compression ignition engine, one option is to blend it with an additive to enhance fuel ignition. Therefore, 5 % of the additive “Beraid” is mixed with 95 % hydrous ethanol. Experiences with approximately 500 urban buses using this fuel mixture for compression ignition engines have been made in Sweden. In October 2007, the first E95 bioethanol bus has been introduced in Brazil (JANSSEN et al. 2007). Also the engine has to be refitted e.g. in that the compression ratio and the volumetric capacity of the fuel pump are increased. The use of material that is compatible to ethanol is a precondition for using ethanol in engines as well. Another option for using ethanol in standard compression ignition engines is to blend ethanol with diesel. It has been shown that a good compromise in terms of fuel economy, performance, drivability and emissions can be achieved when diesel is blended with about 7 % ethanol (WWI 2006). Other approaches of using ethanol in diesel engines are either to use diesel and ethanol simultaneously by “fumigation” or to convert the diesel engine into a spark ignition engine. Although the use of bioethanol in fuel cells is not yet commercially viable, technical applications of ethanol in so called direct-ethanol fuel cells (DEFC) is possible. DEFC systems are a subcategory of proton-exchange fuel cells, also known as polymer electrolyte membrane fuel cells (PEMFC). Their distinguishing features to other fuel cells include lower temperature/pressure ranges and a special polymer electrolyte membrane. When bioethanol is applied to these fuel cells, ethanol is not reformed, but fed directly to the fuel cell. Using bioethanol in DECF applications has several advantages. As it is fed directly into the DEFC, complicated catalytic reforming is not needed. Further, storage of ethanol is much easier than that of hydrogen which is usually used for fuel cells. Storage of liquid ethanol does not need to be done at high pressures, as it is needed for hydrogen, which is a gaseous fuel under normal conditions. Thus, the use of ethanol would overcome both the storage and infrastructure challenge of hydrogen for fuel cell applications. Additionally, the energy density of ethanol far greater than even highly compressed hydrogen. Besides the use of ethanol in DEFC technologies, vehicles could also be equipped with multi-fuel on- board reformers. These devices could continuously generate hydrogen out of ethanol and would enable vehicles to use a combination of conventional and lower-cost fueling systems. Alternatively, commercial-size multi-fuel reformers could generate hydrogen from biofuels on-site at retail stations, avoiding costly hydrogen distribution infrastructure (WWI 2006 p. 223). The use of ethanol as transport fuel is growing in Europe during the last few years. Parallel to this development the need for specifications and standards raised on European level. Since recent times there was no European standard, neither on the utilization of additives in ethanol, nor on ethanol as fuel itself. Consequently the European Commission has inter alia mandated CEN/TC 19 (Comité Européen de Normalisation - Technical Committee 19) to produce a standard on ethanol for blending with petrol. This standard жүктеу/скачать 3,39 Mb. Достарыңызбен бөлісу:
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