Effect of Injection Pressure on the Combustion, Performance, and Emission Characteristics of a Diesel Engine Fueled with Methanol-blended Diesel Fuel

In this study, the effect of injection pressure on the engine performance, exhaust emissions and combustion characteristics of a single cylinder, four stroke, direct injection, naturally aspirated diesel engine has been experimentally investigated when using methanol-blended diesel fuel from 0 to 15% with an increment of 5%. The engine has original injection pressure of 200 bar. The tests were conducted at three different injection pressures (180, 200, and 220 bar) with decreasing or increasing washer number. All tests were conducted at four different loads (5, 10, 15, and 20 N m) for constant engine speed of 2200 rpm. The experimental test results proved that brake thermal efficiency, heat release rate, peak cylinder pressure, smoke number, carbon monoxide and unburned hydrocarbon emissions reduced as brake-specific fuel consumption, brake specific energy consumption, combustion efficiency, and nitrogen oxides and carbon dioxide emissions increased with increasing amount of methanol in the fuel blend. When comparing the results to the original injection pressure, at the decreased injection pressure (180 bar), peak cylinder pressure, rate of heat release, combustion efficiency, and nitrogen oxides and carbon dioxide emissions decreased, whereas smoke number, unburned hydrocarbon, and carbon monoxide emissions increased at all test conditions. On the other hand, with the increased injection pressure (220 bar), smoke number, unburned hydrocarbon, and carbon monoxide emissions diminished, and peak cylinder pressure, heat release rate, combustion efficiency, and nitrogen oxides and carbon dioxide emissions boosted at all test conditions. With respect to brake-specific fuel consumption, brake-specific energy consumption, and brake thermal efficiency, changing injection pressure gave negative results in the all fuel blends compared to the original injection pressure.