Despite one can think that internal combustion engines requirements have determined the development and the spreading of specific fuels, historically it is almost always happened that the availability of fuels characterized by certain properties has conditioned the evolution and the development of the engines and their feeding systems. So liquid fuels derived by the distillation of crude oil have constituted and still constitute the principal energetic source for the engines, due to their large availability and their low cost of production. Almost all the fuels used in internal combustion engines today are liquids produced from crude oil. As well known, this natural mixture has organic origins and derives from the alteration of large masses of animal body mixed to small quantities of vegetable deposits. When oil or someone of its by-products are burnt, energy that was accumulated during thousand of years is developed in few instants. Since oil reserves are in limited number, in the long term it must be considered the hypothesis of an end of the resources. The first oil crisis of the seventies has clearly shown the vulnerability of the prices and of the oil supplies, making the industrialized world to recognize not only the narrowness of the reserves of available energy, but above all, the dangerous dependence from the course of the oil circumstances. All of this has leaded to the search of alternative fuels (or rather derived from sources different than oil) with the purpose to be able to replace the conventional products derived by the crude oil. Initially the main interest has been to find suitable substitutes of the traditional fuels, but recently a great attention has been focused on the use of renewable resources able to reduce in drastic way the emission of carbon dioxide in the atmosphere, deriving from the combustion processes. In the field of alternative fuels for transportation, the employment of alcohols, to be used both pure or in mixture with gasoline, has been considered in different countries, in particular in the South-America, mainly due to economic reasons and to the diversification of the energetic sources, rather than to environmental problems. In fact they are proposed as clean fuels, but actually the alcohols seem to produce little lower CO and HC exhaust emissions compared to those of the correspondent engines fed with gasoline, with a more sensitive reduction of the NOx, while they release, among the unburned hydrocarbons, a great quantity of oxygenated products such as aldehydes, considered strongly harmful for human health. In recent years another fundamental input to the research and development of alternative fuels for engines has been the growing public interest in reducing pollution. In the United States the interest in environmental protection and the dependence from the foreign petroleum has stimulated the production of a specific national legislature and the initiatives of the government. The most important actions were the emanation of the Clean Air Acts Amendments (1990) and the two Energy Policy Acts of 1992 and 2002. Among the initiatives proposed a great deal of programs encourage the use of clean fuels. In this period the American agriculturists (large producers of soy) have shown interest toward alternative uses of the excesses of soybean oil and of other vegetable oils. The concomitance of the two interest started, in the United States, the development and the use a new fuel: the biodiesel. In Europe, biodiesel has reached an appreciable commercial spreading, for example in Germany, France and Italy. The European market is also favorable due to the large diffusion of diesel engine also for passenger cars, besides the heavy-duty applications. The present paper deals with the analysis of performances, emission and combustion of the FIAT 1.9l common rail turbocharged diesel engine, fuelled with blends of diesel and biodiesel. Several studies pertaining to the emission and performance characteristics of biodiesel fuels did not reach unequivocal results and different behaviors have often been registered depending on the engine type, on the operating conditions, on the injection system and on its calibration, etc. Besides, most scientific literature concentrated on diesel engines equipped with conventional injection systems, and even if more recent works also examined engines with high pressure, electronically controlled injection, the analysis has been so far mostly focused on heavy-duty units, while only few studies explored the behavior of last generation passenger car diesel engines. The activity reported in this work starts from a study about the behavior of the mentioned diesel engine fuelled with fossil fuel and with three different pure biodiesel fuels (rapeseed, soybean and waste vegetable oil methyl esters). Further, results about blends usage are presented. Finally, the combustion characteristics of these fuels were also studied in order to attempt a deeper investigation along with the possible engine optimization by means of ECU (Electronic Control Unit) tuning to biodiesel characteristics.

A Comprehensive Study of Biodiesel Suitability for Automotive Engines Applications

GRIMALDI, Carlo Nazareno;MARIANI, Francesco;POSTRIOTI, Lucio;BATTISTONI, MICHELE
2005

Abstract

Despite one can think that internal combustion engines requirements have determined the development and the spreading of specific fuels, historically it is almost always happened that the availability of fuels characterized by certain properties has conditioned the evolution and the development of the engines and their feeding systems. So liquid fuels derived by the distillation of crude oil have constituted and still constitute the principal energetic source for the engines, due to their large availability and their low cost of production. Almost all the fuels used in internal combustion engines today are liquids produced from crude oil. As well known, this natural mixture has organic origins and derives from the alteration of large masses of animal body mixed to small quantities of vegetable deposits. When oil or someone of its by-products are burnt, energy that was accumulated during thousand of years is developed in few instants. Since oil reserves are in limited number, in the long term it must be considered the hypothesis of an end of the resources. The first oil crisis of the seventies has clearly shown the vulnerability of the prices and of the oil supplies, making the industrialized world to recognize not only the narrowness of the reserves of available energy, but above all, the dangerous dependence from the course of the oil circumstances. All of this has leaded to the search of alternative fuels (or rather derived from sources different than oil) with the purpose to be able to replace the conventional products derived by the crude oil. Initially the main interest has been to find suitable substitutes of the traditional fuels, but recently a great attention has been focused on the use of renewable resources able to reduce in drastic way the emission of carbon dioxide in the atmosphere, deriving from the combustion processes. In the field of alternative fuels for transportation, the employment of alcohols, to be used both pure or in mixture with gasoline, has been considered in different countries, in particular in the South-America, mainly due to economic reasons and to the diversification of the energetic sources, rather than to environmental problems. In fact they are proposed as clean fuels, but actually the alcohols seem to produce little lower CO and HC exhaust emissions compared to those of the correspondent engines fed with gasoline, with a more sensitive reduction of the NOx, while they release, among the unburned hydrocarbons, a great quantity of oxygenated products such as aldehydes, considered strongly harmful for human health. In recent years another fundamental input to the research and development of alternative fuels for engines has been the growing public interest in reducing pollution. In the United States the interest in environmental protection and the dependence from the foreign petroleum has stimulated the production of a specific national legislature and the initiatives of the government. The most important actions were the emanation of the Clean Air Acts Amendments (1990) and the two Energy Policy Acts of 1992 and 2002. Among the initiatives proposed a great deal of programs encourage the use of clean fuels. In this period the American agriculturists (large producers of soy) have shown interest toward alternative uses of the excesses of soybean oil and of other vegetable oils. The concomitance of the two interest started, in the United States, the development and the use a new fuel: the biodiesel. In Europe, biodiesel has reached an appreciable commercial spreading, for example in Germany, France and Italy. The European market is also favorable due to the large diffusion of diesel engine also for passenger cars, besides the heavy-duty applications. The present paper deals with the analysis of performances, emission and combustion of the FIAT 1.9l common rail turbocharged diesel engine, fuelled with blends of diesel and biodiesel. Several studies pertaining to the emission and performance characteristics of biodiesel fuels did not reach unequivocal results and different behaviors have often been registered depending on the engine type, on the operating conditions, on the injection system and on its calibration, etc. Besides, most scientific literature concentrated on diesel engines equipped with conventional injection systems, and even if more recent works also examined engines with high pressure, electronically controlled injection, the analysis has been so far mostly focused on heavy-duty units, while only few studies explored the behavior of last generation passenger car diesel engines. The activity reported in this work starts from a study about the behavior of the mentioned diesel engine fuelled with fossil fuel and with three different pure biodiesel fuels (rapeseed, soybean and waste vegetable oil methyl esters). Further, results about blends usage are presented. Finally, the combustion characteristics of these fuels were also studied in order to attempt a deeper investigation along with the possible engine optimization by means of ECU (Electronic Control Unit) tuning to biodiesel characteristics.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11391/37536
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