Experimental and numerical investigation of the effect of fig seed oil methyl ester biodiesel blends on combustion characteristics and performance in a diesel engine

Abstract

Researchers have turned to alternative fuels in diesel engines due to the depletion of fossil fuel reserves, global warming and energy consumption. Among alternative fuels, biodiesel is preferred because of its high oxygen content, better combustion, reliability and no need for any modification in the fuel line. In this study, the combustion characteristics and engine performance processes of biodiesel fuel produced from fig seed oil with different blend ratios were experimentally examined. Up till today, fig seed oil has not been produced as biodiesel and has not been tested in any diesel engine. The biodiesel fuel was produced from fig seed oil for the first time and used in diesel engines. Diesel engine was operated at engine speeds of 1550, 1700, 1850, 2000 and 2150 rpm and full load. 5%, 10% and 20% fig seed oil methyl ester by volume was added to the diesel fuel. The effects of fig seed oil methyl ester with different ratios on in-cylinder pressure, pressure increase rate, net heat release rate, brake specific fuel consumption, engine torque and exhaust gas temperature were evaluated. The combustion characteristics were numerically verified by using AVL Fire. In-cylinder pressure and net heat release rate of diesel and biodiesel fuels were compared numerically and experimentally, and each other close to results were achieved. Experiments show that the fig seed oil methyl ester contributes to the combustion properties of the engine. At 2000 rpm, the in-cylinder pressure’s of diesel, B5, B10 and B20 fuels were 79.29, 81.21, 83.23 and 82.25 bar, respectively. The brake specific fuel consumptions of diesel, B5, B10 and B20 fuels were 274, 279, 281 and 285 g/kWh, respectively. As a result, better combustion has been achieved with %10 biodiesel fuel blend because of the excess oxygen in the biodiesel itself, shorter ignition delay and fast burning.