# Effects of \"S\"-Type Bowed Guide Vanes on Unsteady Flow in 1.5-Stage Axial Compressors
## 4 Conclusions  
In this study, an \"S\"-type bowed guide vane was designed, and a 1.5-stage axial compressor model was established. For five guide vane models with different bending coefficients, an unsteady numerical simulation was carried out under the design condition and the near-blockage condition. The influence of the \"S\"-type bowed guide vane on the overall aerodynamic performance, unsteady flow field distribution, and air flow exciting force is analyzed. The main conclusions are as follows:  
1. The pressure ratio decreases with the increase in the guide vane bending coefficient. Compared with the original straight vane, the pressure ratio under the design condition and the near-blockage condition decreases by 0.18% and 0.22%, respectively, in the \(a=10\) mm models. The total efficiency of the model with the \"S\"-type bowed guide vane is reduced. The total efficiency of the \(a=-10\) mm model decreases the most, which is 0.57% and 0.87% in the design condition and near-blockage condition, respectively.
2. The turbulence kinetic energy near the hub of the guide vane will increase with the increase in the absolute value of the bending coefficient. The turbulence kinetic energy of the guide vane wake under the near-blockage condition is higher than that under the design condition due to the higher velocity. However, in the moving vane passage and the wake of the moving vane, due to the low-pressure ratio under the near-blockage condition, the flow separation caused by the inverse pressure gradient is relatively small.
3. The \(a=5\) mm model will increase the aerodynamic exciting force amplitude on the moving vane. The \(a=-10\) mm model can reduce the tangential and axial aerodynamic exciting force amplitudes under the first-order blade-passing frequency of the moving vane by 90.82% and 90.39% under the design condition, respectively. Under the near-blockage condition, the reduced values are 85.84% and 86.58%, respectively. This is because, for the \(a=-10\) mm model, at different blade heights, the relative position difference between the moving vane leading edge and the guide vane is very large.  
Figure 21: Mach number distribution of the \(a=-10\) mm model under near-blockage conditions.  
This means the uneven flow field at the guide vane outlet may have the opposite effect on the force of the moving vane at different blade heights.  
This shows that the \"S\"-type bowed guide vanes can greatly reduce the aerodynamic exciting force amplitude under the premise of reducing aerodynamic efficiency, which provides an idea for compressor design under some conditions with extremely high requirements for vibration safety. Subsequently, we can consider the design of the moving vane near the end wall to improve the efficiency of the compressor with the \"S\"-type bowed guide vanes.  
Each author has contributed to different work in this study. [PERSON]. ([PERSON]) is mainly responsible for data curation, methodology and writing--original draft. The validation and visualization were completed by [PERSON] ([PERSON]); [PERSON], [PERSON] and [PERSON] undertook the task of writing--review and editing. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Science and Technology Major Project grant number [J2019-IV-0022-0090].  
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Data variability statementData sharing is not applicable to this article.  
All the authors in the paper express great gratitude for the financial support by the National Science and Technology Major Project (J2019-IV-0022-0090).  
The authors declare that they have no known competing financial interest or personal relationships that could have appeared to influence the work reported in this paper.