Performance Research Of Methanol-diesel Blends On Direct-Injected Diesel Engine

With the growing shortage of oil resources and the deterioration of global environment, to find and develop a resource-rich, economically feasible fuel is significant. Methanol is a clean, renewable oxygenated fuel, has very broad application prospects. By the method of adding cosolvents can effectively solve the problem of methanol's poor soluble in diesel fuel, and improve the low-temperature startup performance of mixed fuel. At first, this paper has measured and compared the density, viscosity, heating value, cetane number and other important physical and chemical parameters of the methanol--diesel blends, and deals with the impact of temperature, methanol content on the physical and chemical properties of blends.Meanwhile, the economic performance, combustion and emission characteristics of methanol--diesel blends were investigated without any changes on the structure of the existing diesel engine. The results show that the BSFC of the blends is increased when compared with diesel under the same condition, the ignition delay is extended, the peak heat release rate of premixed combustion increases and the combustion duration is shortened. The blends have higher HC emission than those of diesel, but NO_x and smoke emission is reduced. Under high-load, CO emission decrease significantly.Finally, effects of fuel injection timing on combustion and emission characteristics of the diesel engine fuelled with blends were studied at the maximum torque and rated conditions. The results show that the blends engine almost remained the same economic fuel injection timing. With the increase of fuel injection timing, the ignition delay is extended, the peak heat release rate of premixed combustion increases and the combustion duration is shortened. The NO_x and HC emissions increased with the fuel injection timing advanced, while the smoke and CO emissions decreased. With the decrease of fuel injection timing, the blends have lower rise rate than diesel fuel in smoke and CO emissions. Under the rated conditions, the blends have lower rise rate in NO_x emissions and higher rise rate in HC emissions than diesel fuel when the fuel injection timing advanced.