## 3 Result and Discussion
### CO2 Emission Factor for SSD and HSD  
Figure 8 shows the fuel-based CO2 emissions according to an rpm range of 1-6: 3117.53-3162.57 kg/tonne-fuel for SS1, 3044.75-3136.17 kg/tonne-fuel for SSD 2, 3134.98-3156.19 kg/tonne-fuel for HSD 1, 3100.04-3162.94 kg/tonne-fuel for HSD 2, and 3147.06-3162.61 kg/tonne-fuel for HSD 3. The CO2 emissions from the combustion of 1 ton of fuel are found to not vary significantly depending on the rpm range. The Range 2 section of SSD 2 ships is a critical rpm zone, which should be avoided by rapid acceleration and deceleration to minimize damage due to resonance. Therefore, the difference in trend is considered to be due to the fact that measured data for the SSD 2 Range 2 do not include enough data in a stable state for a sufficient period of time. The amount of CO2 emitted per 1 ton of fuel burned, normalized by the rpm of the five experimental vessels, is shown in Figure 9. The amount of CO2 emitted per ton of fuel over the entire rpm range is mostly distributed between 3050 and 3163 kg, with a mean value of 3148.78 and a standard deviation of approximately 17.71, indicating that there is little difference in the amount of CO2 kg/tonne-fuel depending on the type of engine. Due to the characteristics of the diesel engine, it was confirmed that there was almost no difference in CO2 emissions per 1 ton of fuel burned between SSD and HSD due to perfect combustion over the entire rpm range tested [28]. Figure 8: Fuel-based CO2 emission factor according to rpm range. (**a**) SSD 1; (**b**) HSD 2. Therefore, when calculating CO\({}_{2}\) emissions from ships, the impact of load is expected to be insignificant, and the results of calculating CO\({}_{2}\) emissions based on total fuel consumption are expected to be highly reliable. The CO\({}_{2}\) emissions per fuel amount vary depending on the carbon content in the fuel. Therefore, uncertainties prevail when applying this result to ships using gasoline or LNG. Currently, various fuels, such as LNG and LPG, are used for the main propulsion engines of ships. [PERSON] et al. confirmed that CO\({}_{2}\) emissions from engine exhaust gases vary depending on the carbon content in fuel, as shown in Equation (4) [29; 30]. It is therefore necessary to study the CO\({}_{2}\) emissions for various fuels as follows:  
\[C_{a}H_{2a+2}+\frac{3a+1}{2}O_{2}\rightarrow\mathrm{a}CO_{2}+(a+1)H_{2}O \tag{4}\]  
The operation mode of the ship can be classified as either maneuvering mode (M) or cruising mode (C), except when docked on land. When in cruising mode, the ship operates at a relatively high rpm when sailing in the ocean and can change rpm immediately according to the external environment and traffic volume in the maneuvering mode. As shown in Figure 10, the CO\({}_{2}\) emissions consistent with both maneuvering and cruising modes are shown during the entire experimental period of SSD 1, SSD 2, HSD 1, HSD 2, and HSD 3. Figure 10: Fuel-based CO\({}_{2}\) emissions for maneuvering and cruising modes of each vessel tested. Figure 9: Fuel-based CO\({}_{2}\) emissions distribution according to a dimensionless number of the RPM range for five experimental vessel. In addition, the fuel-based emission factors for SSD and HSD are shown in Table 4 For SSD, the CO\({}_{2}\) emission factors are 3132.36-3156.82 kg/tonne-fuel in maneuvering mode and 3131.44-3149.86 kg/tonne-fuel in cruising mode. In the case of HSD, the corresponding values are 3128.31-3156.30 kg/tonne-fuel and 3147.34-3159.85 kg/tonne-fuel in cruising mode. These findings demonstrate that there is little difference in fuel-based emission factors between operation modes. As such, it was confirmed that there is almost no difference in fuel-based CO\({}_{2}\) emission factors for each operation mode. In the case of SSD, the difference between maneuvering and cruising modes is approximately 0.08% and 0.33% in the case of HSD. In addition, the difference between SSD and HSD is 0.03% in maneuvering mode and 0.38% in cruising mode.