| The burning of biodiesel in the diesel engine brought unsatisfied problem like imperfect combustion, power losing as well as high fuel consumption which arose from the its components property of high viscosity, poor flow ability under low temperature and undesirable atomization and evaporation. This dissertation aims to improve the performance of diesel engine fueled with biodiesel by directly mixed the traditional biodiesel with methanol/ethanol since it take advantages of good viscosity, excellent low temperature fluidity, high ratio of oxygen.The work of this research mainly concentrated in the following aspects:(1)The mutual solubility of the diesel, biodiesel and methanol goes through a remarkable increase as the temperature climbs up under atmospheric pressure since the gradual boosting molecular activity. Experiments show that general commercially available diesel have difficulty in solubility with methanol/ethanol. And compared with ethanol, the solubility between methanol and biodiesel-diesel is lower. However, the biodiesel with light water conforming to the national standards can be low-proportion mixed with unmodified alcohols to produce micro-emulsion.(2)Four types of micro-emulsion fuels named as B95E5, B90E10, B95M5 and B90M10 can be obtained by mixing the biodiesel with volume fraction of 5% and 10% ethanol or methanol respectively. Physical and chemical measured properties indicate that micro-emulsion fuels produced with the former method can effectively reduce the biodiesel0 freezing condensation point, cold filter plugging point and motion viscosity, and the higher mixing ratio the better performance. Also the micro-emulsion fuels’ calorific value declines little and its corrodibility keeps the lowest level. Additionally, The Initial boiling point and flashing point of the new obtained fuel suffer great change.(3)There exist different degrees of receding in the combustion curve, pressure rising rate curve, and instantaneous heat release rate curve of the four type’s micro-emulsion fuels and the receding values decline as the loads increase. The receding values of all the three curves rise as additions of alcohols increase in the same condition. Compared with B100, the peaks of all the four fuels’ combusting pressure, pressure rising rate and instantaneous heat release rate are higher and increase more quickly when the alcohols volume fraction is promoted. The three peaks of micro-emulsion fuels mixed with methanol are all greater than that of ethanol when the mixing rate and the circumstance are same.(4)The micro-emulsion fuels emission the same amount of CO as B100 at small load, but lower amounts of emission are found when the load increase. Also, the CO emission reduces as the engine speed up its rotate rate. Over the load variation range, the micro-emulsion fuels HC emission higher than B100, but small value rise at heavy load. In the test, the NOX emission of B90M10 meet a small decline,but the rest of the several kinds of micro-emulsion fuels no obvious regularity. Also the test shows that the smoke emissions of all the four micro-emulsion fuels are less than that of B100. |
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