## 3 Results and Analysis
### Internal Flow Field of AFT  
#### 3.2.1 Velocity Cloud Diagram  
For all 12 AFT blades, a low-speed fluid region (reg-lv) exists within a certain range at the leading edge of the suction surface (A1 position), where the flow velocity (\(v\)) is less than 2 m/s. A thin reg-lv region also exists along the inner wall of the pipe and on the blade surface. Downstream of position A1 and upstream of the trailing edge of the pressure surface (position B2), a high-speed fluid region (reg-hv) exists where \(v>\) 12 m/s (Figure 10). For the blade pressure surface, the flow \(v\) gradually increases from upstream of A2 to upstream of B2 (blue solid arrow). For the blade suction surface, the velocity decreases gradually from downstream of A1 to downstream of B1 (blue dashed arrow). When \(H\) = 0.18 MPa and \(n\) = 2500 rpm, along the flow direction, the areas of the reg-lv and reg-hv regions gradually decrease. The velocity in the reg-lv region gradually increases, whereas the velocity in the reg-hv region gradually decreases. As M\({}_{1}\) increases from 2 to 4, the area of the reg-lv region on the first blade gradually decreases, but the reg-lv region area on the other blades does not significantly change with M\({}_{1}\). The area of the reg-hv region and its velocity decrease gradually as M\({}_{1}\) increases. Both the area and velocity of reg-lv and reg-hv decrease as M\({}_{2}\) increases, but the changes are relatively small. When M\({}_{2}\) is at a \"medium\" level, M\({}_{3}\) with \"low-high\" (D34, T343, and F3434) and \"high-low\" (D43, T434, and F4343) arrangements has little effect on the flow field. When \(H\) and \(n\) are the same, the reg-hv area and \(v\) of D33 are greater than those of the other AFTs. \begin{table}
\begin{tabular}{c c c c c c c} \hline
**Experimental** & \multicolumn{6}{c}{\(P_{\text{max}}\) (W)} \\
**Treatment** & **H = 0.14 MPa** & **H = 0.15 MPa** & **H = 0.16 MPa** & **H = 0.17 MPa** & **H = 0.18 MPa** & **Ave** \\ \hline D33 & 102.37 & 151.61 & 201.29 & 260.18 & 310.10 & 201.43 \\ D34 & 98.07 & 138.27 & 183.43 & 219.88 & 278.18 & 179.80 \\ D43 & 97.20 & 138.49 & 188.09 & 242.25 & 294.56 & 188.71 \\ D44 & 90.60 & 133.66 & 176.24 & 212.35 & 256.66 & 170.94 \\ Mean & 79.80 b & 140.51 a & 187.76 a & 233.66 a & 284.88 a & 185.22 a \\ T333 & 89.42 & 135.85 & 178.42 & 212.18 & 258.09 & 174.79 \\ T343 & 90.24 & 132.63 & 178.20 & 218.59 & 262.88 & 176.51 \\ T434 & 89.70 & 121.90 & 162.32 & 203.37 & 239.37 & 163.33 \\ T444 & 86.80 & 124.89 & 165.84 & 206.57 & 250.43 & 166.91 \\ Mean & 89.04 a & 128.82 b & 171.20 b & 210.18 b & 252.69 ab & 170.38 a \\ F3333 & 86.09 & 118.51 & 162.21 & 203.92 & 257.51 & 165.65 \\ F3434 & 79.25 & 107.75 & 150.43 & 193.64 & 219.27 & 150.07 \\ F4343 & 80.17 & 109.60 & 144.07 & 186.68 & 219.86 & 148.08 \\ F4444 & 75.81 & 104.14 & 140.18 & 180.25 & 199.24 & 139.92 \\ Mean & 80.33 b & 110.00 c & 149.22 c & 191.12 b & 223.97 b & 150.93 b \\ F value for M\({}_{1}\) & 18.979 & 43.87 & 24.82 & 12.93 & 22.86 & 24.39 \\ Sig-M\({}_{1}\) & ** & * & * & * & * & * \\ F value for M\({}_{2}\) & 0.78 & 8.74 & 5.91 & 3.85 & 8.77 & 8.16 \\ Sig-M\({}_{2}\) & _NS_ & _NS_ & _NS_ & _NS_ & _NS_ & _NS_ \\ F value for & 16.19 & 0.17 & 0.21 & 0.91 & 1.55 & 0.85 \\ Mg-M\({}_{1}\)\(\times\) M\({}_{2}\) & _NS_ & _NS_ & _NS_ & _NS_ & _NS_ & _NS_ \\ \hline \end{tabular} Note: * is significant when \(p<\) 0.05, ** is significant when \(p<\) 0.01, and _NS_ is not significant. The absence of the same letter in each column indicates a significant difference at the \(p<\) 0.05 level.  
\end{table} 
Table 2: Significance analysis of the effects of M1 and M2 on the maximum output power (\(P_{\text{max}}\)) under different inlet pressures (\(H\)). Using D33 as an example, when \(n\) increases from 2000 rpm to 3000 rpm, the area of the reg-lv region gradually decreases, whereas the area and \(v\) of the reg-hv region gradually increase.