Experimental Study On The Fuel-consumption Economy Of Emulsified Fuel In Diesel Engine

Energy shortage and environment pollution are the severe problems that human beings have to face in the 21st century. As main consumer of oil and air pollution source, internal combustion engine attracts researchers'broad interest. How to decrease its fuel consumption and pollutant emission is a challenging field.The combustion of emulsified oil is of great benefit to simultaneous reduction of NOx (nitrogen oxides) and PM (particulate matter) emission, meanwhile, the fuel consumption is lower. But the experiment results show that the rate of economizing fuel is difficult to exceed 4% that obstruct the emulsified oil technique's popularity. The main content of this thesis focus on how to improve the rate of economizing fuel of emulsified oil in diesel engine, and keep the low emission level.Methanol, which can be produced from coal, is an ideal alternative fuel of petroleum in our country. We find that methanol will effectually pyrolyze and generate large amounts of hydrogen when it is heated above 400℃. The ratio of pyrogenation and amount of hydrogen generated increase rapidly with the temperature rise. For example, the ratio of pyrogenation will reach 90% at around 600℃, and we can get 1.8 mol hydrogen from one mol methanol. Methanol can pyrolyze and generate hydrogen when it is heated by the exhaust of diesel engine(temperature range between 400℃and 600℃). Then let the hydrogen generated from methanol go into cylinder with the air directly. By this means, we hopefully increase the rate of economizing oil of emulsified fuel in diesel engine.The results of experimental investigations show that method mentioned above can reduce NOx by 41%, PM by 21%, and the rate of diesel consumption decrease 17%, the rate of economizing fuel reach 12%, the rate of economizing money reach 10.9%. In experiments, we also observe theeffect of the flux of methanol, water content of emulsified diesel and operating power of the engine on the rate of economizing fuel. We find that there are respective optimal values of the flux of methanol and water content to maximize the rate of economizing fuel (flux of methanol 5 mL/min, 15% water content by mass). But the rate of economizing fuel linear decreases with the engine power falling, because the temperature of exhaust is too low to pyrolyze methanol. Here we need additional power supply to heat methanol, and the rate of economizing fuel can revert to 10~12%.Combustion of emulsified fuel is characteristic of optimizing fuel atomization and reducing PM emission in exhaust, which are just the disadvantages of heavy oil combustion. In this work, we try to operate high-speed diesel engine fuelled with industrial heavy oil. Because the viscosity of industrial heavy oil is too high, in experiments, we first mix the heavy oil and diesel in proportion of 1:1 by mass, and then add some water into it to produce emulsified oil as the fuel of diesel engine. Experiment results show that the rate of fuel consumption and PM emission of emulsified mix-oil is almost as much as pure diesel fuel. However the NOx concentration in exhaust decrease remarkably, while CO increase a little. Compared with diesel fuel, the price of industrial heavy oil is much cheaper, so we can get more economic benefits.