Gas Turbine Blade Dovetail Backcut Stress Reduction
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Solution Overview
Problem
Interface locations between blade dovetails and dovetail slots in gas turbine disks are potentially life-limiting due to overhanging blade loads and stress concentrating geometry, with existing dovetail backcuts not optimized to balance stress reduction on the disk, blade, and useful life.
Innovation Solution
A method involving the determination of an optimized start point and cut angle for dovetail backcuts on both blade and disk dovetail slots to maximize stress reduction, useful life, and maintain or improve aeromechanical behavior, with the start point positioned at least 1.945 inches aft from a datum line and a cut angle of up to 5°, using finite element analyses to simulate engine conditions and predict stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If dovetail backcuts are used to relieve stresses at the blade-disk interface, then stress concentrations are reduced, but the useful life of blades and the balance between stress reduction and aeromechanical performance is not optimized
Solution Approach 1:
The patent applies parameter changes by systematically varying the backcut geometry parameters (depth, angle, position) to optimize the balance between stress reduction and blade useful life. Finite element analyses are used to evaluate different parameter combinations and identify the optimal configuration that simultaneously reduces stress concentrations and maintains acceptable blade life and aeromechanical behavior.
Solution Approach 2:
The dovetail backcut modifies the local geometry at the critical interface region between the blade and disk. By creating a localized stress relief feature with specific depth and angle parameters, the patent addresses the stress concentration problem at this specific location without compromising the overall structural integrity and aeromechanical performance of the blade.
2Strength
If material is removed from the blade dovetail or disk dovetail slot, then stress on the disk and blade is reduced, but the aeromechanical behavior of the turbine blade may be compromised
Solution Approach 1:
The patent uses parameter changes to define the backcut geometry (depth, angle, position relative to datum line) such that stress reduction is achieved while maintaining acceptable aeromechanical behavior. The optimized parameters ensure that the backcut provides stress relief without creating detrimental effects on blade performance.
Solution Approach 2:
The patent applies partial action by removing only the necessary amount of material to achieve stress reduction, rather than excessive material removal. The backcut depth and angle are carefully controlled to provide sufficient stress relief while preserving the structural and aeromechanical integrity of the blade.
3Stress or pressure
If the start point of the dovetail backcut is positioned further aft from the datum line, then stress reduction on the disk is maximized, but the stress reduction on the blade and useful life balance may be affected
Solution Approach 1:
The patent systematically varies the start point position parameter (distance aft from the datum line) to optimize the balance between stress reduction on the disk and useful life of the blade. The optimal position is determined through finite element analyses that evaluate the trade-off between these competing objectives.
Data Source
AI summary
Blade load path on a gas turbine disk can be diverted to provide a significant disk fatigue life benefit. A plurality of gas turbine blades are attachable to a gas turbine disk, where each of the gas turbine blades includes a blade dovetail engageable in a correspondingly-shaped dovetail slot in the gas turbine disk. In order to reduce gas turbine disk stress, an optimal material removal area is defined according to blade and/or disk geometry to maximize a balance between stress reduction on the gas turbine disk, a useful life of the gas turbine blade, and maintaining or improving the aeromechanical behavior of the gas turbine blade. Removing material from the material removal area effects the maximized balance.