Influence of gas-to-liquid fuel in the combined blends of biodiesel-diesel / Sajjad Hossain

Energy security concerns and environmental sustainability issues have been increasing with the growth of civilization, which have developed the urge to increase energy efficiency with a diminution in environmental pollution. These situation have stimulated the researchers to focus on the alternative transportation fuels like Gas-to-liquid (GTL) fuel and biodiesel. GTL fuel is produced from Fischer–Tropsch synthesis and consists of some distinctive characteristics such as its paraffinic nature, very low sulfur and aromatic contents and a high cetane number. It can be used as an alternative to diesel and also with the blends of diesel and bio-diesel. Biodiesels are mono-alkyl esters of fatty acids, which can be produced from several widely available feedstock and consist of special features like renewability and diminution of engine emissions, which make those as one of the most potential substitutes for diesel or with the blends with diesel. This study comprises of a comparative analysis of GTL fuel and three potential biodiesel feedstock from Palm, Jatropha and Calophyllum and their blends (20% by vol.) with diesel. Three ternary blends of GTL (20% by vol.), biodiesel (30% by vol.) and diesel (50% by vol.) had been introduced to aggregate the promising properties of these two alternative fuels with diesel, which is a pioneer study involving GTL fuel. The test results of these ternary blends were compared with their respective biodiesel blends (20% by vol.) to investigate the benefits of these blends. All of the fuel samples had been investigated in the context of major fuel properties and the experiments were performed to evaluate engine combustion and several engine performance-emission parameters in a four cylinder compression ignition engine at three different engine test conditions, such as, full load with variable speed, constant speed with variable load and constant torque with variable speed. Combustion analysis results showed that both the peaks of in-cylinder pressure and heat release rate (HRR) of the GTL blend (G20) were slightly lower and occurred at later crank angles than those of the diesel, whereas, the biodiesel blends(B20) and ternary blends (DBG20) demonstrated higher peak values of these two parameters and advanced peak locations than those of diesel. Compared to the B20 blends, the DBG20 blends showed lower peak values of in-cylinder pressure and HRR and slightly retarded peak locations. Performance analysis results showed that both of the B20 and the DBG20 blends showed higher BSFC, BSEC and lower BTE, whereas GTL blend showed lower BSFC-BSEC but higher BTE than those of diesel. Exhaust emission test results demonstrated that all fuel blends showed reduced CO, HC and smoke than diesel. In case of NOx, higher emission was observed for the B20 and DBG20 blends, whereas, GTL blend showed lower emission than diesel. The DBG20 blends showed improvement in all major fuel properties and engine performance parameters like lower BSEC (1.36-2.94%), higher BTE (1.18-3.09%), whereas, emission parameters like CO (4.69-15.48%), HC (2.75-11.89%), NOx (1.15-3.51%) and smoke (2.1-6.35%) than those of their respective B20 blends.