Improvement of Exhaust Gas Emission in Marine Diesel Engine by Blending DME

本文研究了在柴油机上掺烧二甲醚对降低有害排放的作用。二甲醚是一种像传统汽油一样容易着火的化合物。此外，它含有氧，没有直接的碳键。因此，它在燃烧火焰中不会排放碳烟。因此，它可以作为柴油机的代用燃料。另一方面，二甲醚的润滑性很低，会腐蚀橡胶材料。在本研究的实验中，将二甲醚与船用柴油进行了混合，以改善其润滑性。燃料箱采用高压容器，燃料管更换为特氟龙管。通过对供油管线的改进，二甲醚可以用作液化气。直喷式柴油机被改造成可以访问气缸压力历史的测量。在气缸体和气缸盖之间插入间隔环。将压力传感器安装在环上，并测量压力。在实验中，利用气缸压力的时间历程来计算放热率。根据计算的燃烧速率，定义了燃烧区域，以评价燃烧现象的变化。1)掺烧二甲醚可以降低NOx排放。2)掺烧二甲醚可降低碳烟排放。这些趋势在所有发动机速度和发动机负荷条件下都可以看到。在试验工况范围内，掺混二甲醚的比例为40%是降低柴油机排放的最佳条件。结果表明，二甲醚对降低柴油机有害排放是有效的。

In this study, the reduction of harmful exhaust emissions was investigated by use of blending Dimethyl Ether to conventional fuels in a diesel engine. DME is one of chemical compounds those are ignitable as easily as conventional gas oil. Moreover, it contains Oxygen and has no direct carbon bond. Thus, it emits no soot in the combustion flame. So, it is useful as the alternative fuel of diesel engines. On the other hand, its lubricity is very low and it corrodes the rubber materials.In the experiment of this study, DME has been blended with the marine diesel oil in order to improve the lubricity. The high-pressure vessel was used as the fuel tank, and fuel lines were replaced with Teflon tubes. With those modifications in the fuel supplying line, DME was able to be used as the liquefied sate.The direct injection type of diesel engine was modified to access the measurement of cylinder pressure history. The spacing ring was inserted between the cylinder block and the cylinder head. The pressure sensor was mounted to the ring and the pressure was measured. In the experiment, the time history of cylinder pressure was used to calculate the heat release rate. From the calculated rate, the combustion regions were defined in order to evaluate the change in combustion phenomena.From the experiment study, the following results are drawn. 1) NOx emissions could be reduced by blending DME. 2) Soot emissions could be reduced by blending DME. Those trends were seen in all engine speeds and engine load conditions. In the experimental condition range, the mixing rate of 40% DME was the best condition to reduce the exhaust emission in the diesel engine. It is concluded that DME is useful to reduce the harmful exhaust emission in the diesel engine.