# The Optimization of the Geometry of the Centrifugal Fan at Different Design Points
## 3 Results
### Study of Fan Operating Curves
#### 3.2.2 Operating Curves at Second Design Point  
After selecting the optimal geometry parameters at the second design point (DP), it is determined that the impeller with geometry parameters of \(\beta_{1}=12^{\circ}\) and \(\beta_{2}=88^{\circ}\) works  
Figure 7: Operating parameters of optimized impeller at 1 st design point (DP:) (**a**) performance; (**b**) static efficiency. most efficiently. Performance and efficiency curves are determined for a fan with these blade geometry parameters. The characteristics of the fan of the second DP are determined analogously to the curves of the fan at the first DP using SolidWorks software (version is provided in the Section 2) extension \"Flow Simulation\". In the virtual computational domain, the pressure increment of the system is varied, recording the flow dependence at each point. The determined performance curves (Figure 8) show the flow rate (m\({}^{3}\)/h) produced by the fan on the horizontal X axis and the static resistance (Pa) of the system on the vertical Y axis. From the obtained operating curves, it can be seen that the maximum flows generated by the fan at the second DP reach 200, 271, and 343 m\({}^{3}\)/h when the device operates at 1500, 2000, and 2500 rpm, respectively. The maximum static pressure developed by this fan is 50 Pa at an angular speed of 1500 min\({}^{-1}\) and 94.5 and 143.5 Pa at angular speeds of 2000 and 2500 min\({}^{-1}\), respectively. During the virtual tests, the power consumption of the fan is recorded, and the static efficiency is calculated at each point. The graph presented in Figure 8a shows the dependence of static efficiency of the airflow rate. The horizontal X axis shows the amount of air flow (m\({}^{3}\)/h) blown by the fan, and the vertical Y axis shows the static efficiency (%). It can be seen that at an angular speed of 1500 rpm, the maximum static efficiencies of the fan reach 41.3% and 44.1 and 44.5% at angular speeds of 2000 and 2500 rpm, respectively. It should be noted that as the angular speed increases, the value of the maximum efficiency increases as well. Peak static efficiency increases by 2.8% from 41.3 to 44.1% as the speed changes from 1500 to 2000 rpm. As the angular velocity changes from 2000 to 2500 rpm, the efficiency gain drops to 0.4%. Thus, it cannot be stated that the increase in values of angular velocity and static efficiency has a direct relationship. By combining the graphs of the performance and efficiency of the fan at the second DP (Figure 8), it is possible to determine the theoretically most efficient operating modes at the studied angular velocities. Operating at an angular speed of 1500 rpm, the fan achieves maximum efficiency at a system static pressure resistance of 47.5 Pa, producing a flow rate  
Figure 8: Operating parameters of optimized impeller at 2 nd design point (DP): (**a**) performance; (**b**) static efficiency. of 123 m\({}^{3}\)/h. At an angular speed of 2000 rpm, the fan optimized at the second DP is most efficient when blowing 156.5 m\({}^{3}\)/h at 90 Pa static resistance. Operating at the highest tested angular velocity, the fan reaches its theoretical efficiency peak at a pressure of 139 Pa, when it produces an airflow rate of 208 m\({}^{3}\)/h. Considering the results, known literature can be also mentioned. A study published by Chinese researchers in the International Journal of Mechanical Sciences describes the influence of eccentricity on the performance characteristics of a centrifugal fan's leading edge [PERSON] et al. [3]. The results of the experiments led to the conclusion that the data obtained during numerical simulations correlated with the results obtained during real experiments. There was a noticeable difference of 3.05% in the data results when evaluating the increase in static pressure, namely 348.08 Pa from simulations and 337.78 Pa from the experiment. The authors noted that the optimization criteria were appropriate, as the optimized wing's performance characteristics significantly outperformed those of the initial wing.