## 1 Introduction
Among alternative fuel technologies, emulsion fuels are readily producible from conventional fuels, such as diesel, and are a blend of water and emulsifiers added by proportions. Additionally, due to the absorption of the latent heat of evaporation, in turn due to the evaporation of water during the combustion process of a water-containing fuel, it is possible to atomize the fuel due to the lower \begin{table}
\begin{tabular}{|c|c|c|c|c|c|c|c|c|c|c|} \hline \multirow{3}{*}{**Regulation**} & \multirow{3}{*}{**Area**} & \multicolumn{8}{c|}{**Year**} & \multicolumn{2}{c|}{**Remarks**} \\ \cline{3-10}  & & **2013** & **2014** & **2015** & **2016** & **2017** & **2018** & **2019** & **2020** & **2021** & **2022** & \\ \hline \multirow{4}{*}{NOx} & MARPOL & ECA & **Tier II (14.4 g/kWh)** & Tier III (3.4g/kWh, n\textless{}130, 9 n\textless{}^{(-0.2)}\) g/kWh, n\textless{}2000 & \multirow{4}{*}{Similar stage of constructions} \\  & Annex 6 & \multirow{4}{*}{GLOBAL} & & & & & & & & \\  & Regulation & & & & & & & & & \\  & 13 & GLOBAL & & Tier II (14.4 g/kWh) n\textless{}130, n\textless{}130, 44 n\textless{}^{(-0.2)}\) g/kWh, n\textless{}2000 & \multirow{4}{*}{\
\begin{tabular}{} \end{tabular} } & \multirow{4}{*}{
\begin{tabular}{} \end{tabular} } \\ \cline{1-1} \cline{3-10}  & \multirow{4}{*}{SOx} & MARPOL & ECA & **1.0\%S** & & & & & & & \\  & Annex 6 & \multirow{4}{*}{GLOBAL} & & & & & & & & \\  & Regulation & & & & & & & & & \\  & 14 & GLOBAL & & & & & & & & 2025 \\ \hline \multirow{2}{*}{PM} & US-EPA & ECA/ & \multirow{4}{*}{Under Discussions} & US-EPA: Already applied \\  & & & GLOBAL & & & & & & & & \\ \end{tabular}
\end{table} 
Table 1: International Maritime Organization (IMO) Tier III regulation [5]. combustion temperature in the combustion chamber, and the micro-explosion due to rapid evaporation. Thereby, NOx, SO\({}_{2}\), and soot emissions can be reduced simultaneously. In addition, unlike the existing engine technology, new engine combustion technology, and post-treatment technology, no additional device is required, and research has attracted attention because it can be used for an existing engine without any modifications [15; 16; 17; 18; 19]. Among alternative fuel technologies, emulsion fuel refers to a state in which a liquid is mixed with a different liquid, by adding a surfactant to the two liquids, not otherwise well mixing. When producing emulsion fuel using fuel and water, there is an oil-in-water type (O/W) which is water in fuel, and a water-in-oil type (W/O) which is fuel in water. In W/O diesel-water emulsion fuel, micro-explosions occur when water particles evaporate first, due to the difference in the boiling points of water and diesel fuel, when injected into the cylinder. Under normal atmospheric conditions, the boiling point of water is 100 \({}^{\circ}\)C, and the diesel fuel boiling point is 160-400 \({}^{\circ}\)C, depending on the components involved. If the pressure in the cylinder is assumed to be 30 bar when the fuel is injected, the boiling point of the water is about 135 \({}^{\circ}\)C and the water will evaporate before the diesel fuel, under any ambient conditions. When water explodes, the fuels surrounding the water particles are finely divided and then promote fuel atomization [14; 18; 19]. Thus, if atomization is accelerated, soot can be reduced due to combustion improvement. After the water is vaporized, the high evaporative latent heat of water absorbs the heat energy in the combustion chamber, and lowers the combustion temperature, thereby reducing NOx levels. [15; 16] The focus here is on applicability to diesel engines, without the need for additional equipment. However, under low load conditions more exhaust emissions, mainly from incomplete combustion, such as THC (Total Hydro-carbon) and CO (Carbon Oxide) are generated than by existing diesel fuels, and, as high load conditions rise, emissions are similar to conventional diesel fuels [17; 18; 19].