## 4 Results and Discussion
### Algorithm Design Exploration
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Preliminary Design**} \\ \hline \hline  & \multicolumn{4}{c}{**Stator**} & \multicolumn{4}{c}{**Rotor**} \\ \cline{2-7}  & Hub & Mean & Tip & Hub & Mean & Tip \\ \hline Axial Chord (mm) & 6.43 & 6.43 & 6.43 & 9.36 & 6.93 & 4.63 \\ \hline Stagger Angle (\({}^{\circ}\)) & 48.96 & 48.96 & 48.96 & 41.64 & 56.45 & 64.24 \\ \hline Chord (mm) & 9.79 & 9.79 & 9.79 & 12.52 & 12.54 & 10.65 \\ \hline LE Wedge (\({}^{\circ}\)) & 26 & 26 & 26 & 24 & 24 & 24 \\ \hline TE Wedge (\({}^{\circ}\)) & 4 & 4 & 4 & 2 & 3 & 2 \\ \hline LE Thickness (mm) & 0.35 & 0.35 & 0.35 & 0.62 & 0.45 & 0.38 \\ \hline TE Thickness (mm) & 0.17 & 0.17 & 0.17 & 0.22 & 0.22 & 0.22 \\ \hline \multicolumn{7}{c}{**Optimised Design**} \\ \hline \hline  & \multicolumn{4}{c}{**Stator**} & \multicolumn{4}{c}{**Rotor**} \\ \cline{2-7}  & Hub & Mean & Tip & Hub & Mean & Tip \\ \hline Axial Chord (mm) & 6.06 & 5.81 & 6.72 & 6.81 & 5.87 & 5.03 \\ \hline Stagger Angle (\({}^{\circ}\)) & 45.39 & 46.35 & 52.3771 & 39.98 & 52.24 & 63.05 \\ \hline Chord (mm) & 8.63 & 8.42 & 11.01 & 8.89 & 9.59 & 11.10 \\ \hline LE Wedge (\({}^{\circ}\)) & 28 & 27 & 28 & 27 & 27 & 27 \\ \hline TE Wedge (\({}^{\circ}\)) & 3.43 & 5.37 & 5.85 & 4.88 & 5.37 & 5.37 \\ \hline LE Thickness (mm) & 0.39 & 0.32 & 0.23 & 0.75 & 0.43 & 0.43 \\ \hline TE Thickness (mm) & 0.22 & 0.20 & 0.22 & 0.23 & 0.19 & 0.16 \\ \hline \multicolumn{7}{c}{**Percentage Change**} \\ \hline \hline  & \multicolumn{4}{c}{**Stator**} & \multicolumn{4}{c}{**Rotor**} \\ \cline{2-7}  & Hub & Mean & Tip & Hub & Mean & Tip \\ \hline Axial Chord (mm) & \(-\)5.75\% & \(-\)9.64\% & 4.51\% & \(-\)27.24\% & \(-\)15.30\% & 8.64\% \\ \hline Stagger Angle (\({}^{\circ}\)) & \(-\)7.29\% & \(-\)5.33\% & 6.98\% & \(-\)3.99\% & \(-\)7.46\% & \(-\)1.85\% \\ \hline Chord (mm) & \(-\)11.85\% & \(-\)13.99\% & 12.46\% & \(-\)28.99\% & \(-\)23.52\% & 4.23\% \\ \hline LE Wedge (\({}^{\circ}\)) & 7.69\% & 3.85\% & 7.69\% & 12.50\% & 12.50\% & 12.50\% \\ \hline TE Wedge (\({}^{\circ}\)) & \(-\)14.25\% & 34.25\% & 46.25\% & 144.00\% & 79.00\% & 168.50\% \\ \hline LE Thickness (mm) & 11.43\% & \(-\)8.57\% & \(-\)34.29\% & 20.97\% & \(-\)4.44\% & 13.16\% \\ \hline TE Thickness (mm) & 29.41\% & 17.65\% & 29.41\% & 4.55\% & \(-\)13.64\% & \(-\)27.27\% \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Comparison between preliminary parameters and optimised parameters. Table 5 shows initial pre-optimised blade geometries and percentage difference with the final blade, respectively. As shown by the percentage change section, the more significant changes were achieved by rotor trailing edge wedge angles among all layers, as well as stator trailing edge wedge angles at median and tip layers. Wedge angles increase was also met with a considerable hub leading edge rotor thickness and stator trailing edge thickness among all layers. This is in accordance with what was already discussed, with blades tending towards higher thicknesses. Figures 10 and 11 below are a meridional side view of the blade profiles, visualising part of what is presented in Table 5. The more prominent difference when comparing the blade to the preliminary optimisation result, shown in Figure 11, is the stator tip being closer to the rotor. By guiding the flow further in the stage, the stator achieves faster speeds at rotor inlet, allowing more kinetic energy in the system, which can then be harvested by the rotor. Another important change in side view blade geometry is the dramatic change in chord length. Optimised blades tend to be shorter at hub and median layers and, as presented later, thicker. A possible explanation would be that flow through the blade would experience choking and considerable losses on longer blades, thus causing the chord reduction. Having thicker blades would increase the safety factor, as well as flow speed in the throat area, leading to possibly a more efficient energy harvesting mechanism. Figures 12 and 13 show thickness contours for preliminary and optimised blades.