## 4 Analysis of Experimental Results  
### Load Characteristic Analysis  
The ice-propeller milling experiments were conducted in air and water. Ice-water-propeller interaction experiments included atmospheric pressure and decompression test conditions. Therefore, considering the operating conditions four to six in Table 3 as examples, the time-domain variation curve of the propeller load and the ice-propeller milling process under ice-propeller interaction in three different environments are shown in Figures 7 and 8. In Figure 7, ice-propeller milling was conducted in air, and the load on the propeller at this time is the ice milling load. Ice-water propeller denotes the blockage and milling test of ice and propeller in water, and the test environment corresponds to atmospheric pressure and decompression conditions, respectively. In Figure 8, the following three processes are depicted: milling near the ice block, leading edge milling, and full-contact milling. Figure 6: Different rotation positions of the key blade and the coordinate system. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{\begin{tabular}{c} **Test** \\ **Conditions** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Depth of Cut** \\ **\(\mathbf{h/D}\)** \\ **\end{tabular} } & \begin{tabular}{c} **Cavitation** \\ **Number of** \\ **Rotational** \\ **Speed at 0.8R** \\ \end{tabular} & \begin{tabular}{c} **Ice Moving** \\ **Speed \(\mathbf{V}\)** \\ **(mm/s)** \\ \end{tabular} & \begin{tabular}{c} **Advance** \\ **Coefficient \(\mathbf{J}\)** \\ **Speed \(\mathbf{n_{m}}\) (r/s)** \\ \end{tabular} & \
\begin{tabular}{c} **Rotational** \\ **Speed \(\mathbf{n_{m}}\) (r/s)** \\ \end{tabular} &
\begin{tabular}{c} **Inflow Speed** \\ **\(\mathbf{V_{m}}\) (m/s)** \\ \end{tabular} \\ \hline Case 1 & 1/16 & Air & 30 & 0 & 19.36 & 0 \\ Case 2 & 1/16 & Atmospheric & 30 & 0.281 & 19.36 & 1.36 \\ Case 3 & 1/16 & \(\sigma\) = 0.44 & 30 & 0.281 & 19.36 & 1.36 \\ Case 4 & 1/16 & Air & 30 & 0 & 22.15 & 0 \\ Case 5 & 1/16 & Atmospheric & 30 & 0.325 & 22.15 & 1.8 \\ Case 6 & 1/16 & \(\sigma\) = 0.33 & 30 & 0.325 & 22.15 & 1.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Test operating conditions. Figure 8: Milling process of ice and propeller in air and water: (**a**) Ice-propeller milling test (in air); (**b**) Ice-water-propeller milling test (atmospheric pressure); (**c**) Ice–water–propeller milling test (\(\sigma\) = 0.33). Figure 7: Time-domain curves of propeller load under ice-propeller interaction in different environments: (**a**) \(T\); (**b**) \(Q\). During ice-propeller milling in air, shown in Figures 7 and 8a, the propeller has no milling action during \(t=0\)-1.45 s. At this time, the ice milling load of the propeller changes at approximately 0 N and 0 N\(\cdot\)m, with the relative movement of the ice block, axial force, and torque of the propeller increasing gradually at \(t=1.45\)-2.25 s. From Figure 8a, it can be concluded that during this period, the ice and leading edge of the blade came in contact. With the movement of the ice and rotation of the propeller, the depth of cut and contact area of the blade gradually increased. Due to the fact that the contact area is proportional to the ice milling load [6; 30], the ice milling load of the propeller gradually increases. Moreover, it was observed that the ice milling load of the propeller was positive. In \(t=2.25\)-4.52 s, the ice milling load of the propeller had a stable periodic change, which indicated that the ice-propeller milling process had stabilized, as shown in Figure 8a. However, the axial force of the propeller appeared as alternately positive and negative, and the load in the positive direction was greater than that in the negative direction, which was mainly due to the combined action of the axial and tangential forces of the blade, whereas the propeller torque was almost entirely positive.