## 3 Results and Discussion
### Experimental Verification of the Effects of Airfoil on Fan Performance  
Figure 18 shows the original A airfoil fan model. To confirm the validity of the simulation outcomes, a multi-blade fan model incorporating the A airfoil design was constructed and subjected to separate tests for the airfoil and single-arc fan options. After designing the A airfoil fan model, a result test was conducted under the same experimental conditions as the prototype. Upon comparison, the maximum absolute error between the  
Figure 17: Comparison results of (**a**) efficiency and (**b**) total pressure.  
simulation value and the experimental value was 4.28 Pa, which is within the acceptable error range. Therefore, it can be considered that the CFD calculation is reliable and the verified experiment is feasible. As shown in Figure 16a,b, these are the velocity cloud diagrams of the fan section under different flow rates. In the case of a small flow rate (Case 2), the flow condition of the single-arc model is poor, and the velocity distribution in the impeller region is more uneven than that of the A airfoil model, which is more obvious in the red box area shown in Figure 16a,b. It should be noted that a severe blocking effect occurs in both models at the rotating surface, which is caused by the too-small gap between the motor and the impeller blades. However, at 90\({}^{\circ}\) < 0 < 180\({}^{\circ}\), the high-speed region of the A airfoil model in the impeller-volute gap is significantly higher than that of the single-arc model and the jet-wake is weaker in the tail region of the runner.  
Table 5 summarizes the design parameters of the multi-blade centrifugal fan employed in the verified experiments, which were specifically optimized to satisfy the operational demands of a high-performance household range hood's internal fan.  
Figure 19 shows a performance comparison between the A airfoil fan and the single-arc fan. The performance efficiency of the A airfoil fan is generally higher than that of the single-arc fan when the flow starts from 100 m\({}^{3}\)/h (see Figure 19a). This indicates that the airfoil design scheme of the multi-blade centrifugal fan presented in this study can significantly improve the fan efficiency, and the maximum increase in efficiency is approximately 7%. The efficiency in the common working conditions range has also increased by 3% to 7%, and the high-efficiency flow range has been increased from 450 m\({}^{3}\)/h to 650 m\({}^{3}\)/h. In addition, the results show that the fan with the A airfoil designed as a blade improves the angle of attack of the fluid entering the impeller and reduces the sensitivity of the angle of attack.  
It can be seen from Figure 19b that the total pressure of the A airfoil fan is higher than that of the single-arc fan when the flow rate exceeds 300 m\({}^{3}\)/h. In general, the average value is 50 Pa higher, and the improvement ratio reaches more than 20%. Especially in the high flow area, the pressure characteristics of the A airfoil fan are greatly improved. Figure 19c shows that the power of the A airfoil fan is lower than the single-arc fan when the flow rate is below 350 m\({}^{3}\)/h, with a maximum reduction of 25 W. The above results indicate that the airfoil design can greatly reduce the power consumption of the fan and achieve the purpose of energy conservation.  
Figure 18: The experimental fan of the A airfoil.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Fan Parameter** & **Single-Arc Fan** & **A Airfoil Fan** \\ \hline Volume flow (m\({}^{3}\)/h) & 0–700 & 0–701 \\ \hline Total pressure (Pa) & 0–310 & 0–310 \\ \hline Rotating speed (r/min) & 1500–2700 & 1500–2700 \\ \hline Axle power (W) & 50–110 & 50–111 \\ \hline Temperature (\({}^{\circ}\)C) & 25 & 25 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Design parameters of the multi-blade centrifugal fan.