| Summary: | 碩士 === 國立成功大學 === 機械工程學系 === 88 === This study is focused on the combustion characteristics, engine performance, and pollution analysis of different ratios of ethanol-gasoline blended fuels (E0,E5,E10,E20,E30). This study includes three parts, the experiments, the theory analysis of stagnation plane spray combustion, and the engine test.
Throughout the experiment, we use stagnation plane spray burner to investigate the combustion characteristics of different ratios of ethanol-gasoline blended fuels. The results show that, with increasing ethanol content in the blend fuel, the equivalence ratio of the system when extinction gets higher. From the temperature analysis, we conclude that the flame speed of the blended fuel with less than 20% ethanol is mainly affected by the fuel-air equivalence ratio of the system. The characteristic of higher latent heat and lower heat of combustion of the ethanol will not show effects until the ration of ethanol in the blend fuels is over 30%.
In theory analysis, we develop a model for the stagnation plane spray combustion to analyze the phenomena of fully pre-evaporized spray combustion and investigate factors that affect the combustion phenomena. These factors include concentration of gas fuel, flame stretch rate, Lewis number, the amount of liquid fuel and the ratio of ethanol in the blended fuels. The results of the theory analysis coincide with the results of experiments of stagnation plane spray combustion.
During the engine test, we use different ratios of ethanol-gasoline blended fuels with different rpms and different throttle valves of engine as test conditions. The results show that using ethanol-gasoline blended fuels slightly increase the torque output and fuel consumption while the emissions of CO and HC decrease as a result of leaning effect due to addition of ethanol, the emission of CO2 increases as a result of better combustion situation. At last, emission of NOX depends on the operating condition of engine.
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