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It is investigated of the DME spray characteristics about varied ambient pressure and fuel injection pressure using the common rail fuel injection system when the nozzle holes diameter is varied. The common rail fuel injection system and fuel cooling system is used since DME has compressibility and vaporization in atmospheric temperature. The fuel injection quantity and spray characteristics were measured. The spray was analyzed of spray shape, penetration length, and spray angle at the six nozzle holes. The 2 type injectors were used, the one was 0.166 mm diameter the other one was 0.250 mm diameter. The ambient pressure which is based on gage pressure was 0 MPa, 2.5 MPa, and 5 MPa. The fuel injection pressure was varied by 5 MPa from 35 MPa to 70 MPa. When using the converted injector, compared to using the common injector, the DME injection quantity was increased 127 % but it didn't have the same heat release. Both of the common and converted injectors had symmetric spray shapes.

The effect of ambient gas hydrocarbon content on diesel spray ignition and combustion was examined in this research project. A single-stroke rapid compression machine was used to prepare the ambient gas pressure and temperature before the diesel fuel injection process. Variations of ambient gas composition were achieved by adding different quantities of methane and propane to the intake air, the content ranged from 0.0 to 0.6 equivalence ratio. The two-color method was applied to analyze the flame temperature and KL factor was determined from the colored flame image taken by a high-speed camera. Also, compression ignition characteristics of lean methane-air and propane-air mixtures were examined.

The effect of intake oxygen concentration on both the flame temperature and emission of NOx and particulates from a direct injection diesel engine is reported. Nitrogen oxide emissions from a direct injection diesel engine was correlated with calculated stoichiometric flame temperature, yielding -143,000 cal/mole for the overall activation energy for the processes involved. It was found that when In (EIP) was plotted against the inverse of flame temperature at a range in load between 0% to 100% the values of In(EIP) are linear. Analyzing the slope gave a constant apparent activation energy. But the correlation of In(EIP) with flame temperature at 110% load shows smaller activation energy than that at lower load conditions.

The mixing process of fuel with the surroundings are necessary to verify combustion process and then to make a combustion model. In this study, a single shot of diesel spray is injected through either a constant pressure injection system or bypass type injection system which has the same characteristics as the one of an actual engine. Measurement are made on the gas velocity distribution around the spray and its time history using a hot wire anemometer. The gas flow direction is determined by the smoke tracer method. In this investigation the axial and radial distributions of entrainment air are determined, and also their time histories are observed. Radial distribution of the entrainment velocity can be shown ū(t) = CrA and the entrainment coefficient αe is estimated to be a volume between 0.2 ∼ 0.3.