# Fatigue Damage Assessment of Turbine Runner Blades Considering Sediment Wear
## 5 Conclusions  
This paper takes a mixed-flow hydraulic turbine from a high-head hydropower station as the research subject and investigates the changes in the fatigue life of the turbine runner caused by blade wear during actual operation. The main conclusions are as follows:  
Figure 12: The total fatigue damage of the blade considering wear and without wear.  
As the turbine blades continuously wear, there is no significant change in the maximum pressure at the runner inlet, while the negative pressure at the outlet significantly increases. By analyzing the pressure fluctuations on the working and worn surfaces of the blade wear areas, it was found that as wear increases, the pressure fluctuations at the blade tail gradually strengthen, the negative pressure on the worn surface of the blades gradually decreases, and the pressure on the working surface slowly increases. Therefore, as the amount of blade wear increases, it can lead to unstable flow and cavitation near the outlet edge of the blades, which in turn affects the energy conversion efficiency of the runner and reduces the fatigue life of the blades.
2. At different stages of blade wear, the maximum stress is always located at the connection area between the blade outlet edge and the lower ring, and the gradient of equivalent stress variation at this position is quite significant, with stress concentration effects also being quite pronounced. Therefore, fatigue damage tends to initiate preferentially in this area, which is entirely consistent with the actual sites of fatigue damage on turbine blades. Moreover, as the blades continue to wear, the overall stress level in the danger zone keeps increasing.
3. As the blades continuously wear down, the fatigue damage in the critical areas of the blades increases progressively before they are worn away. The total fatigue damage at the danger points, when considering blade wear, shows a significant increase compared to the fatigue damage at the danger points without considering wear. This has a substantial impact on the calculation of the blade's fatigue life. Therefore, in basins with high sediment content, the calculation of the fatigue life for hydraulic turbine runners should take into account the effects of sediment wear on the blades.  
Through the research presented in this paper, the pattern of fatigue damage progression over operating time for a mixed-flow hydraulic turbine, considering wear, has been established. Calculations indicate that the fatigue life of the hydraulic turbine, when wear is taken into account, is approximately 8 years, which aligns with practical conditions. This provides valuable insights for the safe and reliable operation and maintenance of hydraulic turbine units in the future.  
Conceptualization, H.C. and J.P.; formal analysis, H.C. and S.W.; funding acquisition, J.P.; investigation, J.M. and W.Z.; methodology, H.C. and J.P.; project administration, J.P.; resources, S.W., J.M. and W.Z.; software, H.C., J.P. and S.W.; supervision, S.W.; validation, H.C., J.M. and W.Z.; visualization, H.C.; writing--original draft, H.C.; writing--review and editing, H.C. and J.P. All authors have read and agreed to the published version of the manuscript.  
This research was funded by Special Support Plan for High-Level Talents in Zhejiang Province (No. 2021R52036).  
Not applicable.  
The raw data supporting the conclusions of this article will be made available by the authors on request.  
The authors would like to thank Zhejiang Sci-Tech University. This work was supported by Special Support Plan for High-Level Talents in Zhejiang Province (No. 2021R52036).  
The authors declare no conflicts of interest.