# Effects of \"S\"-Type Bowed Guide Vanes on Unsteady Flow in 1.5-Stage Axial Compressors
## 3 Results and Discussion
### Unsteady Aerodynamic Results under Near-Blockage Conditions  
Table 5 shows the pressure ratio and total pressure of different guide vane bending coefficients under near-blockage conditions. The effect of the guide vane bending coefficient on the overall aerodynamic performance is consistent with that of the design condition under the condition of near-blockage. The pressure ratio decreases with the increase in  
Figure 14: Mach number distribution of the \(a=-10\) mm model under design conditions. bending coefficients. When the bending coefficient \(a=10\) mm, the pressure ratio decreases by 0.22% compared with the prototype. The total efficiency of the \"S\"-type bowed models is reduced. The total efficiency of the structure with \(a=-10\) mm decreases the most, which is 0.8%. In addition, the pressure ratio and total efficiency under the near-blockage condition are generally lower than that in the design condition. Figure 15 shows the turbulent kinetic energy distribution of models with different bending coefficients at different axial positions of the moving vane under near-blockage conditions at the time \(t=0\) T. The left figure is the front 2 mm position of the moving vane, which is the inflow of the moving vane. The middle figure is the middle position of the moving vane passage. The right figure is the back 2 mm position of the moving vane, which is downstream of the moving vane. The turbulent kinetic energy distribution of the near-blockage condition is similar to that of the design condition on the whole, but it is different locally. The difference is that the turbulent kinetic energy intensity in the guide vane wake region under the near-blockage condition is higher than that under design conditions. This is due to the  
Figure 15: Turbulent kinetic energy distribution of different models under near-blockage condition. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Bending Coefficient \(a\)/mm** & \(\mathbf{-10}\) & \(\mathbf{-5}\) & \(\mathbf{0}\) & \(\mathbf{5}\) & \(\mathbf{10}\) \\ \hline pressure ratio & 1.1651 & 1.1637 & 1.1636 & 1.1632 & 1.1610 \\ total efficiency/\% & 80.87 & 81.59 & 81.74 & 81.72 & 81.21 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Overall aerodynamic performance under near-blockage conditions. greater flow of near-blockage conditions. When the boundary layer on the guide vane surface is transformed into a turbulent boundary layer, the turbulence intensity is higher, which leads to higher turbulent kinetic energy of the guide vane wake. In addition, the turbulent kinetic energy intensity downstream of the moving vane under near-blockage conditions is obviously lower than that under the design conditions. This is because for the 1.5-stage axial compressor, the pressurization process is mainly completed in the rotor passage. Therefore, the flow in the moving vane channel is inverse the pressure gradient flow, which will cause more serious flow separation on the moving vane surface, making the turbulent kinetic energy of the moving vane wake larger. The pressure ratio of the near-clogging condition is smaller, so the flow separation caused by the inverse pressure gradient is lighter. Figures 16 and 17 show the tangential and axial exciting force-time domain distribution on the moving vane of different models under near-blockage conditions. In the \(a=-5\) mm, \(a=0\) mm, \(a=5\) mm, and \(a=10\) mm models, the time-domain distribution is close to the form of the sine function. The time-domain distribution of the aerodynamic exciting force of the \(a=-10\) mm model is very different from other models. The time-domain distribution of the air flow exciting force under near-blockage conditions is analyzed using a fast Fourier transform, and the spectrum distribution is obtained as shown in Figure 18. The amplitude of the \(a=-10\) mm model is much lower than that of other models. Table 6 shows the time mean value and the amplitude value at the first-order blade-passing frequency of the aerodynamic exciting force with different bending coefficients.