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This study presents the effects of fuel blends containing 5%, 10%, 15% and 20% of anhydrous ethanol in diesel oil with 20% of biodiesel (B20) on performance, emissions and combustion characteristics of a diesel engine. The engine was tested with its original configuration and in the lower brake specific consumption region, at 1800 RPM. The results showed that in-cylinder peak pressure and heat release rate increased with the use of ethanol. The use of ethanol increased ignition delay and decreased exhaust gas temperature. Brake specific fuel consumption increased with ethanol addition, and fuel conversion efficiency was not affected. Increasing ethanol content in the fuel caused decreased carbon dioxide (CO2), carbon monoxide (CO) and total hydrocarbons (THC) emissions.

The solubility of ethanol in diesel oil with biodiesel is a limiting factor for its use as fuel for compression ignition engines. The stability of blends of ethanol with concentration varying from 5% to 30% in diesel oil containing 7% of biodiesel (B7) was evaluated at temperatures from 16°C to 25°C. The blends were conditioned in graduated glass cylinders and kept at the test temperatures, being observed the blend phase separation percentage in specific time schedules. The results show the stability time of each blend, indicating the maximum storage and use periods for the ethanol concentration evaluated. The results demonstrate that fuel blends with ethanol concentrations up to 15% can safely be used as engine fuels, as far as the tested parameters are concerned.