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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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This work aims to analyze the operation of a generator set on single fuel mode with diesel oil, and on dual fuel mode using diesel-ethanol blends. The engine used to realize the experimental analysis was a diesel cycle model, single cylinder, direct injection, air refrigerated and coupled to a three-phase electric generator, whose set capacity was 8.0 kVA. The generated electric energy was dissipated in electrical resistances inside a reservoir with running water. Fuels were blended in different volumetric ratios, using a small portion of vegetable castor oil to promote the homogenization. The percentages of substitutions of diesel oil were from 10% to 50%, increasing by 10% the replacement for each sample. Also, the engine was operated with 100% substitution of diesel oil, i.e., for this condition, the samples were composed of ethanol/castor oil 90/10 (volume/volume), 80/20 and 75/25. The blends of diesel and ethanol did not obtain good performance, mainly in taxes of substitution above 40%, causing combustion failures, operational instability, and increase of fuel consumption, although it has achieved a greatly reduction on opacity percentages. The blends with 100% of substitution of diesel oil obtained good performance except to blend with 90% ethanol, where occurred combustion failures, which caused operational instability. To these conditions, the results achieved are increase of consumption by 17%, decrease of opacity by 79%, decrease of exhaust gas temperature by 3.5% and increase of engine thermal efficiency by 1.3%. At the ethanol -castor oil blends there was a decrease in the percentage of opacity by 96%, decrease of exhaust gas temperature by 17.6%, with a minimum of operational irregularities, although fuel consumption has increased by 52.4% and the engine thermal efficiency has decreased almost 1.7%.