TY - GEN

T1 - Robust Probabilistic Analysis of Deterioration-Induced Aeroelasticity in an Axial Turbine

AU - Stania, Lennart

AU - Seume, Joerg R.

N1 - Funding Information: The present work has been carried out in the subproject C4 within the Collaborative Research Center (CRC) 871 ”Regeneration of Complex Capital Goods” funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – SFB 871/3 – 119193472. The authors would like to thank the DFG for the support. Moreover, the authors would like to acknowledge the substantial contribution of the DLR Institute of Propulsion Technology for providing TRACE. This work was supported by the LUH compute cluster, which is funded by the Leibniz University Hannover, the Lower Saxony Ministry of Science and Culture (MWK) and the DFG. Thus, the authors acknowledge the support of the cluster system team in the production of this work. Last, we thank Pedro Henrique Calderaro Ro-drigues for his help creating the probabilistic chain and an initial data set.

PY - 2022/10/28

Y1 - 2022/10/28

N2 - The surface of a real-world turbine blade differs from the geometry of its model. Manufacturing tolerances, wear, and regeneration during the turbine's lifetime impact the aerodynamic behaviour, stage efficiency, and parameters as previous probabilistic studies have shown. Aerodynamic changes lead to aeroelastic variances in downstream rows that can have a significant impact on high-cycle fatigue due to a possible increase of a blade's vibration amplitude. The present study expands an existing tool chain to uni-directional aeroelastic full three dimensional simulations. The test object is the last stage of a lowpressure five-stage axial turbine; the geometric variances are applied to characteristic airfoil parameters of the vane by Latin hypercube sampling. A required sample size for an accurate sensitivity analysis is estimated a-priori and verified by computational simulations. The aerodynamic analysis identified the stagger angle, trailing-edge thickness, maximum thickness, and maximum camber as the most important parameters among the characteristic blade parameters. For large deviation in the stagger angle a non-monotonous influence on isentropic efficiency was found, which shows limitations of a sensitivity analysis based on the Spearman rank correlation coefficients. A variance-based sensitivity analysis was used for a more detailed analysis, which is capable to detect such non-monotonous relationships. In the aeroelastic simulations, the chord length, maximum camber, and the trailing-edge angle have the highest influence on aerodynamic forcing and damping on a downstream rotor blade of the changed stator blade. Furthermore, direct correlations between aerodynamic stage parameters and aerodynamic damping are shown, which allows reduced order modelling. The correlation between work coefficient and vibration amplitude was overlooked by the Spearman's coefficient but identified by the variance-based approach. A maximum vibration amplitude is identified, indicating a potential of using probabilistic studies for adjusting the safety factors for high-cycle fatigue during the design process of blades.

AB - The surface of a real-world turbine blade differs from the geometry of its model. Manufacturing tolerances, wear, and regeneration during the turbine's lifetime impact the aerodynamic behaviour, stage efficiency, and parameters as previous probabilistic studies have shown. Aerodynamic changes lead to aeroelastic variances in downstream rows that can have a significant impact on high-cycle fatigue due to a possible increase of a blade's vibration amplitude. The present study expands an existing tool chain to uni-directional aeroelastic full three dimensional simulations. The test object is the last stage of a lowpressure five-stage axial turbine; the geometric variances are applied to characteristic airfoil parameters of the vane by Latin hypercube sampling. A required sample size for an accurate sensitivity analysis is estimated a-priori and verified by computational simulations. The aerodynamic analysis identified the stagger angle, trailing-edge thickness, maximum thickness, and maximum camber as the most important parameters among the characteristic blade parameters. For large deviation in the stagger angle a non-monotonous influence on isentropic efficiency was found, which shows limitations of a sensitivity analysis based on the Spearman rank correlation coefficients. A variance-based sensitivity analysis was used for a more detailed analysis, which is capable to detect such non-monotonous relationships. In the aeroelastic simulations, the chord length, maximum camber, and the trailing-edge angle have the highest influence on aerodynamic forcing and damping on a downstream rotor blade of the changed stator blade. Furthermore, direct correlations between aerodynamic stage parameters and aerodynamic damping are shown, which allows reduced order modelling. The correlation between work coefficient and vibration amplitude was overlooked by the Spearman's coefficient but identified by the variance-based approach. A maximum vibration amplitude is identified, indicating a potential of using probabilistic studies for adjusting the safety factors for high-cycle fatigue during the design process of blades.

UR - http://www.scopus.com/inward/record.url?scp=85141381199&partnerID=8YFLogxK

U2 - 10.1115/GT2022-82628

DO - 10.1115/GT2022-82628

M3 - Conference contribution

AN - SCOPUS:85141381199

T3 - Proceedings of the ASME Turbo Expo

BT - ASME Turbo Expo 2022: Turbomachinery Technical Conference and Exposition

PB - American Society of Mechanical Engineers(ASME)

T2 - ASME Turbo Expo 2022: Turbomachinery Technical Conference and Exposition (GT 2022)

Y2 - 13 June 2022 through 17 June 2022

ER -