The purpose of this article is to investigate the effects of an unmodified small engine operating on diesel oil-natural gas (DO-NG) and soybean vegetable oil-natural gas at intermediate load. This is significant to reduce our dependency from diesel oil and the emissions of warming gases. Although it is important to highlight that the literature regarding this experimental conditions is scarce, due the use of soybean vegetable oil and natural gas in dual-fuel mode, characterizing a totally diesel oil replacement. The experiments were conducted in a single-cylinder diesel engine coupled to a generator. Natural gas was introduced at the engine intake manifold. The diesel oil and soybean vegetable oil substitution rates were from 16.6 to 91.1% and from 17.6 to 90.7%, respectively. The experimental results were satisfactory being observed a decrease in specific fuel consumption (until 80% of replacement) and a maximum reduction around 80% in NO x emissions. On the other hand, there have been an increase in CO emissions and a decrease in thermal efficiency for all conditions performed. Soybean vegetable oil-natural gas operation demonstrates same trends with a little higher specific fuel consumption and NO x emission than DO-NG.
This study investigates the operation of a diesel engine (compression ignition) coupled to an alternator, using mixtures of diesel oil and hydrous ethanol as fuel, with high water content. The mixtures of ethanol and water were injected at the intake manifold (fumigation), while the diesel oil was injected directly in the combustion chamber. The mixtures of ethanol and water were prepared with 90, 80 and 70% of ethanol, at volumetric fraction. The analyzed parameters were energetic and exergetic efficiency, specific fuel consumption, exhaust gas opacity and exhaust gas temperature. The results have shown that the increase of water in hydrous ethanol causes reduction of efficiencies (energetic and exergetic) and increase the specific fuel consumption, however, the gas opacity and the exhaust gas temperature are reduced. Despite the reduction of efficiencies, the use of ethanol with high water fraction is viable because there is potential for fossil fuel substitution by a renewable source. Economically, it was verified that for each condition tested there is a maximum cost of ethanol for viability, and only in 4 out of 27 Brazilian states the use of fumigation of ethanol/water blends technique would be viable, but with the lowest water concentration.
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