| Summary: | 碩士 === 國立雲林科技大學 === 機械工程技術研究所 === 86 === This research is to study the engine operating parameters and the fuel additives on the diesel engine emissions and the relationship between the emissions. This study can provide an insight to the diesel engine combustion characteristics and the effect of the fuel additives on the combustion processes. The research is done against a YAMAHA ME200F 3-cylinder DI diesel engine.This study is separated into two parts. First, with the engine operating conditions as the controlling variable the engine emissions and the deposit characteristics are studied. The diesel engine exhaust gas temperatures are measured as an indication of the in cylinder charge temperature while a complete set of gas analyzer is used to measure the NOX, H C, COX concentrations and the smoke opacity. The deposit sample is collected in the solutions after continuous 25 hours engine operation and then the solution is dries up to measure the deposit weight. The SEM device is used to study the deposit size and its crystal formation characteristics. The EDS device is used to study the deposit''s element composition. The second part of this research is to study the effect of the fuel additives on the exhaust emissions. The controlling parameters is the engine load, the engine speed, the brand of fuel additives, and the dosage of the fuel additive. The measured data including the exhaust gas temperature, the exhaust emissions, and the smoke opacity.Results show that increase of engine load and/or decrease of the engine speed will increase the NOX emission concentration. The HC concentration first goes up and then goes down as the engine speed and /or load is increase. This is beca use the increased in cylinder turbulence strength and the high temperature effects will promote the oxidation of residual HC vapor in cylinder. The smoke opawill increase with the engine load and/or speed which has the same trend as the temperature features. The deposit particle size and the deposit crystal size both first increase then decrease with the increase of engine load and/or speed. The fuel additives can have substantial effects on the engine''s fuel spray penetration, fuel-air mixing processes, ignition delay, chemical reaction rates, and total heat release. Certain additives have positive effects on the reduction of exhaust emissions; however, it is not necessary that the effects are all positive and significant enough on every emissions (Temperature, NOX, HC, and Smoke). It is not guaranteed that all these seven additives can reduce the emission concentrations, there are certain testing results show the opposite trend in this study. It seems to has optimized dosages for specific fuel additives to bring down the emission levels; however, it is not necessary that further increase of additive dosage will promote the reduction of the emission l evels.According to the results shown in this research the effects of engine operating conditions on the engine exhaust emissions and the deposit formation are examined. The effects of fuel additives on the emissions are also analyzed systematically. Thus, the thrust of this research is to understand the spray combustion characteristics in the diesel engine and the modification in these processes due to fuel additives. The knowledge found in this research can be used to search a compromised way for both reduction in the emissions and maintaining the same engine operating performance.
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