An Improved Approach to HCF Development for Vaneless Turbine Stages
This paper highlights the steps that have been taken to improve the design, analysis, measurement and verification of HCF in vane less turbine stages, the intent being to improve both the HCF robustness and maintain performance. In making these improvements the impact on the aerodynamic performance of the turbine stages was also strongly considered to ensure that improvements made for HCF were not made at the expense of performance. The investigation of these new design options required developments in analytical capabilities, specifically 3D unsteady CFD, in order to make the necessary iterations with adequate fidelity in a practical timeframe. To verify the analysis techniques comprehensive experimental measurement of blade strain levels across multiple designs was also conducted and the results compared with analysis. Finally endurance testing was conducted to confirm that the measured improvements in HCF resulted in longer (and sufficient) service life of the turbine stage. Estimation of the required service life was accomplished using the process presented by Kulkarni et al (IMechE 2010).