Using CFD to Reduce Resonant Stresses on a Single-Stage, High-Pressure Turbine Blade

Abstract

The ability to predict levels of unsteady forcing on high-pressure turbine blades is critical to avoid high-cycle fatigue failures. In this study, 3D time-resolved computational fluid dynamics is used within the design cycle to predict accurately the levels of unsteady forcing on a single-stage high-pressure turbine blade. Further, nozzle-guide-vane geometry changes including asymmetric circumferential spacing and suction-side modification are considered and rigorously analyzed to reduce levels of unsteady blade forcing. The latter is ultimately implemented in a development engine, and it is shown successfully to reduce resonant stresses on the blade. This investigation builds upon data that was recently obtained in a full-scale, transonic turbine rig to validate a Reynolds-Averaged Navier-Stokes (RANS) flow solver for the prediction of both the magnitude and phase of unsteady forcing in a single-stage HPT and the lessons learned in that study.

Study on the Effect of Asymmetric Vane Spacing on Vibratory Stress of Blade

“…This method is the almost same one that Clark et al adopted in their work [9]. They solved the 3D time-resolved flow-field twice, and concatenated the first blade signals in time to get a result of full-wheel analysis.…”

“…[6,7]. Besides these methods, it is well known that the asymmetric vane spacing can result in decreased levels of the excitation force at specific frequencies [8,9]. It seems that asymmetric vane spacing is a very effective method for controlling the blade response for variable speed engines where the axial rotor span cannot be lengthened.…”

“…This paper proposes a practical analysis method for predicting the response reduction due to asymmetric vane spacing using 3-D CFD and the modal analysis method based on 3-D FEM. This method is the almost same one that Clark et al adopted in their work [9]. With this method, a time-history wave of vibratory stress is predicted for both the symmetric and asymmetric vane spacings.…”

Low-Heat-Load-Vane Profile Optimization, Part 1: Code Validation and Airfoil Redesign

“…However, a number of researchers have used computational fluid dynamics (CFD) in conjunction with optimization techniques in other areas of study. Clark et al [3] used 3-D time-resolved CFD to predict unsteady forcing levels on a single-stage high-pressure turbine blade to ultimately explore asymmetric vane spacing designs and use gradient-search optimization techniques to redesign the suction side of a blade. First-torsion stresses in this work were successfully reduced by 50%, resulting in a prototype engine that reduced resonant stresses by 36%.…”

Study on Vibration Characteristics of Mistuned Bladed Disk(Vibration Response Analysis by Reduced Model FMM)

“…The asymmetric vane spacing has been proposed as one of the effective methods to reduce the resonant stress caused by the interaction between the vane and the blade (1) (2) . The authors proposed a method for predicting the response reduction effect of the asymmetric…”