## 4 Ventilation Cooling Optimization Schemes with Non-Uniform Core Segments
### CFD Simulation Analysis  
Based on Table 2, the solution models for the above three schemes are established. The CFD finite element method is used to solve and calculate the fluid-thermal coupling model, as Figures 13 and 14. The original design and three optimization schemes are further analyzed. By comparing the finite element results of different schemes, the performance of each scheme is evaluated, and the optimal scheme is selected from them.  
Figures 14 and 15 show the temperature distributions of the generator's stator and whole structure, respectively, under different non-uniform core segment arrangements. After changing the arrangement, the stator side temperature changes significantly. The three schemes feature a marked drop in the highest temperature and a more even heat distribution, especially in Scheme 3.  
By observing the temperature distribution of the stator core, it is evident that the size of the core has an impact on the temperature of the stator core, as shown as Figure 16. Figure 16 compares the axial temperature distribution curves of the windings and core for the three optimized schemes versus the original scheme. In the original design, the stator core's temperature is lower on both ends and higher in the middle, with the peak temperature occurring between Core Segments 8 and 12. In Scheme 1 and Scheme 2, the  
Figure 14: Temperature comparison of different schemes: (**a**) origin; (**b**) scheme 1; (**c**) scheme 2; (**d**) scheme 3.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Structural Scheme** & **Core Segment** & **Radial Ventilation Ducts** \\  & **(Axial Length (mm) \(\times\) Number)** & **(Axial Length (mm) \(\times\) Number)** \\ \hline Origin & 63.4 \(\times\) 20 & 6 \(\times\) 19 \\ Scheme 1 & 67.4 \(\times\) 3 + 60.4 \(\times\) 8 + 63.4 \(\times\) 6 + 67.4 \(\times\) 3 & 6 \(\times\) 19 \\ Scheme 2 & 67.4 \(\times\) 3 + 63.4 \(\times\) 6 + 60.4 \(\times\) 8 + 67.4 \(\times\) 3 & 6 \(\times\) 19 \\ Scheme 3 & 67.4 \(\times\) 3 + 63.4 \(\times\) 3 + 60.4 \(\times\) 8 + 63.4 \(\times\) 3 + 67.4 \(\times\) 3 & 6 \(\times\) 19 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Non-uniform core design schemes.  
thinner C-group core segments are placed on the left and right sides respectively. In Scheme 1, the maximum temperature appears on the right side of the stator, while in Scheme 2, it appears on the left side. The maximum temperature in Scheme 1 is 52.79 \({}^{\circ}\)C, a decrease of 2.18 \({}^{\circ}\)C (about 3.97%) compared to the original one. In Scheme 2, the maximum temperature is 52.81 \({}^{\circ}\)C, a decrease of 2.15 \({}^{\circ}\)C (about 3.91%). Although both schemes lower the overall temperature, the temperature difference on both sides of the core remains significant. In Scheme 3, placing the C-group core segments in the center position significantly reduces the temperature peak. The maximum temperature is 51.56 \({}^{\circ}\)C, a decrease of 3.41 \({}^{\circ}\)C (about 6.4%) compared to the original one. This arrangement also makes the temperature distribution more uniform, proving effective in suppressing the temperature peak.  
For the winding, the axial temperature distribution is similar to that of the core segments, but the overall temperature of the winding is higher than that of the core. Scheme 1 and Scheme 2 can respectively reduce the temperature on the left and right sides, while Scheme 3 can balance the disadvantage of the middle section in heat dissipation capacity, reducing the temperature gradient, and thereby mitigating the potential risks to generator operation caused by thermal stress. Considering all factors, Scheme 3 was chosen as the final optimized scheme.