# Economic Feasibility of Retrofitting an Ageing Ship to Improve the Environmental Footprint
## 2 Retrofitting the Propulsion System
### Ship Performance  
The operating parameters of both engines are shown in Table 3. The output power of the engines is the same. Additionally, of utmost importance is that the 500 rpm operating speed has not changed, so there will be no need to change propeller shafts, gearboxes and propellers to take power off. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline  & & & & & \multicolumn{4}{c}{**Dimensions**} & & & & \multicolumn{1}{c}{**Weight**} \\ \cline{2-10}
**Engine Type** & & & & & **[mm]** & & & & & & \\ \cline{2-10}  & **L1** & **L2** & **L3** & **L4** & **H1** & **H2** & **H3** & **W1** & **W2** & **[t]** \\ \hline
6M43C & 8251 & 1086 & 1255 & 1583 & 4258 & 1399 & 750 & 2878 & 215 & 94.0 \\
6M46 DF & 8271 & 1086 & 1255 & 1638 & 4258 & 1396 & 750 & 2878 & 215 & 94.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The primary dimension of both engines. The specific fuel consumptions are indicated in Table 4, in which the values are given separately depending on the mode of operation of diesel or gas and for the different working loads of the engine, being converted into tons per hour for easy comparison. It is important to note that the dual-fuel engine has a higher diesel consumption than the currently installed engine. This is a negative point for the dual fuel, which, when running on diesel, will consume more than the current engine, giving the ship less autonomy. The big difference is mainly because the new engine has a pilot pre-ignition system. The speed of a ship depends on the power generated and one can see from the running characteristics of the considered ship in Table 5.  
To obtain the gas consumption in tonnes or cubic meters per hour, it is necessary to know the Lover Calorific Value (LCV) and the fuel gas density. Depending on the composition of the gas, these properties may have different values. However, the variation range is small that the average values of LCV = 49.5 (KJ/g) and density of 0.45 t/m\({}^{3}\) can be used. The gas consumption in tonnes or cubic meters per hour is presented in Table 6. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Load, \%**} & \multicolumn{2}{c}{**6M43C**} & \multicolumn{2}{c}{**6M46 DF**} \\ \cline{2-6}  & **Diesel (g/kWh)** & **Diesel (l/h)** & **Diesel (g/kWh)** & **Diesel (l/h)** & **Gas (l/h)** \\ \hline
100 & 177 & 0.708 & 188 & 0.752 & 0.619 \\
85 & 176 & 0.598 & 187 & 0.636 & 0.534 \\
75 & 177 & 0.531 & 189 & 0.567 & 0.480 \\
50 & 185 & 0.370 & 195 & 0.390 & 0.335 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Fuel consumption of 6M43C and 6M46 DF engines. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{1}{c}{**Performance Data**} & **Unit** & **6M43C** & **6M46 DF** \\ \hline Maximum continuous rating acc. ISO & kW & 5400 & 5400 \\
3046/1 & Speed & 1/min & 500/514 & 500/514 \\ Minimum speed & 1/min & 300 & 300 \\ Brake mean effective pressure & bar & 24.4/23.7 & 21.3/20.7 \\ Charge air pressure & bar & 3.65 & 3.55 \\ Firing pressure & bar & 208 & 150 \\ Combustion air demand (ta = 20 \({}^{\circ}\)C) & m\({}^{3}\)/h & 33,100 & 32,050 \\ \hline \hline \multicolumn{1}{c}{Specific fuel oil consumption} & & \\ \hline \(n\) = 100\% & g/kWh & 176 & 186 \\
85\% & g/kWh & 175 & 185 \\
75\% & g/kWh & 177 & 187 \\
50\% & g/kWh & 184 & 192 \\ Lube oil consumption & g/kWh & 0.6 & 0.6 \\ NO\({}_{\text{x}}\) emission & g/kWh & 10 & 10 \\ Turbocharger type & & ABB TPL71 & ABB TPL71 \\ \hline Fuel & & & \\ \hline Engine-driven booster pump & m\({}^{3}\)/h/bar & — & — \\ Stand-by booster pump & m\({}^{3}\)/h/bar & 4.2/10 & 4.2/10 \\ Mesh size MDO fine filter & mm & 0.025 & 0.025 \\ Mesh size HFO automatic filter & mm & 0.01 & 0.01 \\ Mesh size HFO fine filter & mm & 0.034 & 0.034 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Operating parameters of 6M43C and 6M46 DF engines. The natural gas consumption under standard ISO conditions corresponds to the natural gas in the liquid state at 100%, 85%, 70% and 50% MCR, respectively.