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

本文研究了柴油机掺烧二甲醚对有害排放物的影响。二甲醚（DME）是一种与常规柴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，它在燃烧火焰中不排放烟灰。因此，它是有用的柴油机的替代燃料。另一方面，二甲醚润滑性差，对橡胶材料有腐蚀作用，本研究将二甲醚与船用柴油进行调合，以改善船用柴油的润滑性。高压容器被用作燃料箱，燃料管道被特氟龙管取代。通过对供油管路的改造，使二甲醚可以作为液化油使用。对直喷式柴油机进行了改造，使其可以进行缸内压力历程的测量。将隔环插入缸体和缸盖之间。将压力传感器安装到环上并测量压力。在实验中，缸内压力的时间历程被用来计算放热率。根据计算的燃烧速率，确定了燃烧区域，以评价燃烧现象的变化。1)掺烧二甲醚可降低NOx排放。2)掺混二甲醚可以降低碳烟排放。这些趋势在所有发动机转速和发动机负载条件下都可以看到。在本试验条件范围内，掺烧40%二甲醚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物是有益的。

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.