# Effects of an Inclined Blade on the Performance of a Sirocco Fan
## 3 Results and Discussion  
### Validation against Experimental Results  
In this section, we compare the numerical results for the baseline model with those obtained by the experiment to validate the accuracy of the numerical simulation. The variations in static pressure and efficiency with flow rate are shown in Figure 6. For the static pressure, there was a certain deviation between the numerical and experimental results at small (\(Q\)/\(Q_{n}=0.483\)) and rated flow rates (\(Q\)/\(Q_{n}=1.000\)), while the two values were quite in consistent under high flow rate conditions. For the static pressure efficiency, there was a certain deviation between the computed and the experimental results at rated and high flow rates (\(Q\)/\(Q_{n}=1.760\)); however, the results of the simulation and experiment were quite consistent at other flow rates, and the variation trends of both results were the same. The results show that the maximum deviation between numerical and experimental results was less than 6.9% for the static pressure and was less than 4.6% for the efficiency. It is concluded that the steady simulation results were generally in agreement with the experimental results, and the computed results can provide a useful reference for the design of the actual fan. \begin{table}
\begin{tabular}{c c} \hline \hline
**Component** & **Number of Nodes/10\({}^{3}\)** \\ \hline Rotating wheel domain & 5640 \\ Inlet duct domain & 1120 \\ Outlet duct domain & 300 \\ Volute domain & 420 \\ All & 7480 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Number of nodes of the computational domain. Figure 5: Validation of static pressure rise with node number. The efficiency describes the performance of the fan \(\eta\), which is defined as:  
\[\eta=\frac{30000 PQ}{3600\times 10^{3}\pi Tn}, \tag{8}\]  
in which \(P\), \(Q\), \(T\), and \(n\) represent static pressure (Pa), flow rate (m\({}^{3}\)/h), torque (N\({}^{\star}\)m), and rotation speed of the impeller (rpm), respectively. The impellers with blade inclination angles of 3.5\({}^{\circ}\), 7.0\({}^{\circ}\), and 10.5\({}^{\circ}\) were denoted as model-A, model-B, and model-C, respectively. Through numerical simulation and analysis, the aerodynamic performances of fans with the three types of impellers were obtained. Figure 7 shows the effect of inclination angle on the static pressure and efficiency. The curves of the static pressure of model-A (\(\theta\) = 3.5\({}^{\circ}\)) and model-C (\(\theta\) = 10.5\({}^{\circ}\)) were close to that of baseline fan for the majority of the whole range of flow rate, which reflects that the static pressure of the fan was only increased slightly. However, model-B (\(\theta\) = 7.0\({}^{\circ}\)) is preferred for increasing the static pressure for both medium and high flow rates, whereas the values were less than that of the baseline fan for low flow rates. In particular, the static pressure of model-B increased significantly under high flow rates. Compared with the static pressure of the baseline model, it can be seen that under the high flow rate, the static pressure of model-B increased by 14.01 Pa. Figure 7b shows the effect of inclination angle on the static pressure efficiency (the efficiency of the motor is removed). It can be seen that for both medium and high flow rates, model-B produced increasing static pressure efficiency. However, the values were consistent with the baseline fan under low flow rates. Meanwhile, the static pressure efficiencies of model-A and model-C were slightly higher than that of the baseline fan for the majority of the working range. It was further found that under the rated flow rate, the improvement of the static pressure efficiency of model-B was up to 2.7%, and the improved static pressure efficiency of model-B rose as much as 9.35% at high flow rates compared with that of the baseline model. Figure 6: Comparison of characteristic quantities for steady flow simulation: (a) static pressure–flow rate curve; (b) static pressure efficiency–flow rate curve.