The effect of added ethanol to diesel fuel on performance, vibration, combustion and knocking of a CI engine

Gasoline and diesel as fossil fuels are widely used in industry and agricultural field, and have different performance, combustion and vibration characteristics in the internal-combustion engines. Added biofuels to fossil fuels effect on the mentioned characteristics. Ethanol is considered as a renewable fuel in different countries, which is produced from plant, sugary and starchy biomass. Ethanol as an important additive to gasoline and diesel fuel can improve the engine performance and reduce emissions. In this study, the ethanol was added to pure diesel fuel with concentrations of 2, 4, 6, 8, 10, and 12%. The produced torque and power, brake thermal efficiency (BTE), combustion, and vibration levels were evaluated. For this, a six cylinders CI engine in the five rotational speeds of 1600, 1700, 1800, 1900, and 2000 rpm was used under full load mode. The results showed that the torque and power increase on average by 3.8% at fuel blend with concentration of 6% ethanol (D94E6) as compared with those of pure diesel fuel. For this fuel, the RMS and kurtosis of vibration on the engine block enhance 4.75% and 7.75% as compared with pure diesel, respectively, that shows the more shocks is created. The RMS value is more dependent on engine speed, while kurtosis value is more sensitive to the fuel blend. Despite the increase in power for the D94E6 fuel blend, some irregularity is observed in engine performance, and engine works more non-uniform. It seems that with increasing the ethanol concentration more than 8% in diesel fuel, ignition delay rises and engine operates irregularity. In other words, the pressure changes are increased inside the cylinders and knocking is occurred. (C) 2016 Elsevier Ltd. All rights reserved.