## 4 Conclusions  
The suboptimal performance of centrifugal fans can lead to additional energy waste. In this study, the blades of the fan were optimally designed to improve ventilation efficiency and reduce energy consumption. A feasible and practical structure optimization scheme of the fan was proposed. The internal flow characteristics and flow field distribution of a multi-blade centrifugal fan were analyzed using CFD numerical calculations and verified through experiments. Through the analysis of velocity flow fields and velocity vectors under different working conditions, it was found that the A airfoil fan exhibited more uniform velocity distribution and fewer vortex phenomena under both low and high flow conditions. Particularly under high flow conditions, the A airfoil fan had a more uniform velocity distribution, more stable flow, and fewer vortices, indicating that the A airfoil fan performed excellently in suppressing secondary flows within the impeller blades. Further analysis showed that the A airfoil fan also had a relatively uniform pressure distribution under different working conditions, especially under high flow conditions, with a smaller pressure gradient, reducing pressure fluctuations on the blade surface. This uniform pressure distribution helped to reduce noise and vibration during fan operation, improving the operational stability and lifespan of the fan. In summary, the multi-blade centrifugal fan with A airfoil blades significantly improved efficiency performance in the study object but did not show a noticeable effect in improving total pressure performance. By optimizing blade design and improving flow field distribution, the A airfoil fan demonstrated higher efficiency and better stability in practical applications. Figure 19: Performance comparison of the A airfoil fan and the single-arc fan: (**a**) efficiency, (**b**) total pressure, and (**c**) input power. Flow field analysis was conducted on four airfoils (A, B, C, and D) using the lift-to-drag ratio theory. The results indicated that the A airfoil exhibited the most superior flow characteristics. The numerical simulations of the fan model with airfoil blades revealed a positive correlation between the lift-to-drag ratio and efficiency under specific working conditions, while the effect of total pressure is not significant. The performance of the A airfoil centrifugal fan was compared with that of the single-arc centrifugal fan. The results demonstrated that energy consumption was significantly reduced and efficiency improved by 2-3% in the centrifugal fan with the A airfoil. This improvement is attributed to the design of the A airfoil, which reduces flow separation and inhibits secondary flow. The efficiency, total pressure, and input power of the A airfoil blade fan were compared with that of the single-arc blade fan through verified experiments. The trial-optimized fan exhibited a 3-7% improvement in efficiency and a higher efficiency flow range compared to the prototype fan. The total pressure data showed a 20% increase in the optimized differential pressure value and the test power data demonstrated significant energy consumption reduction. Overall, the experimental results validate the reliability of the numerical simulations. However, further studies are needed to identify other factors that may affect the internal flow of the fan, and exploring even better airfoil designs is necessary. In the course of this study, the blade profile design was carried out using airfoils, with a focus on investigating the impact of the lift-to-drag ratio on multi-blade centrifugal fans. However, the influence of structural parameters of the airfoil, such as airfoil thickness and camber, on multi-blade centrifugal fans has not been thoroughly studied. Future research needs to investigate the performance of multi-blade centrifugal fan blades under different airfoil parameter conditions. In addition to improving fan efficiency, it is also necessary to suppress noise in multi-blade centrifugal fans.