Investigation on the structural effects of the addition of alcohols having various chain lengths into the vegetable oil-biodiesel-diesel fuel blends: An attempt for improving the performance, combustion, and exhaust emission characteristics of a compression ignition engine

Abstract

The scarcity of petroleum-based fuels and the augmentation of pollution levels have been the major parameters in the charge of the investigation of new and promising alternative fuel blends that can be used for the compression-ignition (CI) engine applications. In this context, the researches on renewable and sustainable fuels like vegetable oils, biodiesel, and alcohol for diesel engines have kept intensively for a long time. But, pure vegetable oils or biodiesel fuels may not be operated unaccompanied in diesel engines because of their high viscosity and density values. Accordingly, there is a great potential for the utilization of quaternary blends of biodiesel vegetable oil, alcohol, and diesel fuel in order to enhance the density and viscosity. In the present study, diesel fuel was blended with biodiesel (safflower oil methyl ester), biodiesel-vegetable oil (safflower oil), and biodiesel-vegetable oil-alcohol (ethanol-C2, isopropanol-C3, n-butanol-C4, or isopentanol-C5) mixture. The test fuels of diesel–biodiesel (80–20%), diesel–biodiesel-vegetable oil (70–20–10%), and diesel–biodiesel-vegetable oil-alcohol (60–20–10–10%) blends were prepared by the splash blending technique and experimented in a single-cylinder, four-stroke, air-cooled, direct-injection diesel engine generator set in order to investigate the performance, combustion and exhaust emission characteristics at five different engine loads (0, 500, 750, 1000, and 1250 W) with a fixed engine speed of 3000 rpm. The engine test results revealed that brake specific fuel consumption of the fuel blends increased between 4.54% and 27.82% compared to the diesel fuel while decreasing in brake thermal efficiency due to lower calorific value. In general, the overall emission values of all the tested fuel blends mitigated as compared to diesel. The combustion characteristics showed that the addition of various alcohols into the ternary blends led to rising in-cylinder pressure with decreased heat release rate. It is concluded that the diesel–biodiesel-vegetable oil-pentanol blend could be a suitable fuel mixture to improve the performance, combustion behaviors and reducing exhaust emissions.