The effects of fuel injection pressure on combustion and emission characteristics of a diesel engine using frying oil methyl ester

The application of biodiesel has become more significant in the current decades owing to the environmental aspects and rapid exhaustion of petroleum fuel reserves. In the present study, the influence of fuel injection pressures on engine performance and emission results has been evaluated in a diesel engine using frying oil methyl ester. The waste frying oil was filtered, transesterified and employed in the diesel engine for the experimental analysis. The experiment has been conducted with biodiesel different fuel injection pressures of 220?bar, 240?bar and 260?bar to investigate the performance, combustion and emission parameters in a direct injection (D.I) diesel engine under constant speed (1500?r.p.m) and varying load condition. In the present experimental work, the performance and emission results of the engine have been taken initially with diesel fuel at the injection pressure of 220?bar as the reference reading. The results show that the brake thermal efficiency of the engine with biodiesel increased by 8.94% and 16.09% when the fuel injection pressure is raised from 220?bar to 240?bar at the rated power condition. The CO, HC and smoke emissions were significantly reduced by 22.32%, 14.23% and 29.03% respectively at the injection pressure of 260?bar due to superior combustion. But on the other hand, the oxides of nitrogen emissions rise with fuel injection pressure for the biodiesel fuel. At higher fuel injection pressure especially at 260?bar, the engine fueled with biodiesel has better control over CO, HC and smoke emissions, and the performance results were improved and comparable with the results of conventional diesel fuel.