## 3 Automatic Intelligent Optimization
### Orthogonal Design Optimization
#### 3.2.2 Analysis of Optimization Results  
The comparison results of the optimized scheme 2 with the original scheme 1 is shown in Table 8. As seen from it, the heads of each assessment point are improved after optimization, in detail, the efficiency at design flowrate is increased by 3.66%, and the weighted average efficiency of the optimization scheme is increased by 3.29%. Figure 11 shows the comparison of the external characteristic curves obtained from the CFD. It is clear that the head of the optimized pump is higher than the model pump, and the head curve is shifted to the direction of large flow. It can be seen from the \(\eta\)-\(Q\) curve that the flow rate at best efficiency point increased slightly. The efficiency improvement under large flow conditions is very obvious. Thus, the high efficiency region is effectively broadened. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Source of Variance**} & \multicolumn{4}{c}{_f(X) \%_} \\ \cline{2-5}  & **A** & **B** & **C** & **D** \\ \hline Sum of squared deviation \(SS_{T}\) & 4.269 & 1.929 & 19.263 & 1.098 \\ Degree of freedom \(f_{T}\) & 2 & 2 & 2 & 2 \\ Mean square error \(SS_{E}\) & 1.1 & 1.1 & 1.1 & 1.1 \\ Statistics value \(F_{k}\) & 3.888 & 1.757 & 17.544 & 1 \\ Significance & Insignificant & Insignificant & Significant & Insignificant \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Analysis of variance. Figure 12 shows the comparison of pressure distribution at mid-span of the impeller under three flowrates. Figure 12a-c represent the results of the original scheme and Figure 12d-f represent the results of the optimized scheme. As seen from them, the pressure inside the impeller passage increases from leading edge to trailing edge under all three different flowrates and appears largest near the impeller outlet. The pressure on the blade working surface is greater than the pressure on the back side of the corresponding position, and the low-pressure area appears on the suction side of the blade near the impeller inlet. As the flow rate increases, the area of the low-pressure area gradually expands. Under \(1.25Q_{\text{d}}\), a reverse pressure gradient appears on the inlet part in the optimized impeller. The pressure distribution in the optimized pump impeller is more uniform than in the original one, and a relatively less obvious pressure gradient is present inside the impeller flow-path than the original one. Figure 11: Comparison of external characteristic curves between origin and optimization scheme: (a) Head; (b) Efficiency. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Operation Points**} & \multicolumn{2}{c}{**H/m**} & \multicolumn{2}{c}{**\(\eta\)/\%**} & \multicolumn{2}{c}{**Weighted Average Efficiency \%**} \\ \cline{2-7}  & **Original** & **Optimal** & **Original** & **Optimal** & **Original** & **Optimal** \\ \hline \(0.8Q_{\text{d}}\) & 7.6 & 7.9 & 50.1 & 52.17 & & \\ \(1.0Q_{\text{d}}\) & 6.7 & 7.3 & 51.4 & 55.06 & 49.93 & 53.22 \\ \(1.25Q_{\text{d}}\) & 5.35 & 6.15 & 47.97 & 51.8 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Comparison of the performances under specified conditions. Figure 12: _Cont._  
Figure 13 illustrates the distribution of the turbulence kinetic energy at mid-span of the impeller under three flowrates. Figure 13a-c represent the original scheme, Figure 13d-f represent the optimized scheme. It can be concluded that the maximum turbulence kinetic energy is prone to appear on the suction side of the blade. As the flow rate increases, the turbulence kinetic energy in the impeller gradually increases for both schemes. The turbulence kinetic energy of the optimized pump is smaller than the original one. Under \(1.0Q_{d}\), the distribution of turbulence kinetic energy in the flow-path is the most uniform both before and after optimization. Under \(1.25Q_{d}\), the kinetic energy distribution of the optimized pump is more even. Overall, the flow field has been improved after optimization.