Gas Turbine Blade Platform Undercut Stress Relief
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Solution Overview
Problem
Gas turbine blades experience high mechanical and thermal stresses at the trailing edge, leading to potential cracking and failure due to inadequate stress relief and cooling in existing designs.
Innovation Solution
The introduction of undercuts on the platform of the gas turbine blade, combined with enhanced cooling through a serpentine passageway system, to reduce mechanical and thermal stresses and improve cooling efficiency at the trailing edge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional turbine blade design without undercuts is used, then manufacturing is simpler, but mechanical and thermal stresses at the trailing edge are not adequately relieved leading to crack initiation and blade failure
Solution Approach 1:
The platform is segmented by introducing undercuts that create distinct regions (first undercut, second undercut, and intermediate region) with different stress characteristics. This segmentation allows each region to be optimized for stress relief, preventing crack initiation at the trailing edge while maintaining overall blade integrity.
Solution Approach 2:
The undercut configuration creates local quality variations in the platform structure. The first and second undercuts have different orientations and depths, creating zones with optimized stress distribution characteristics. This local differentiation allows targeted stress relief at critical trailing edge regions without compromising overall blade strength.
2Temperature
If conventional cooling passages are used, then cooling air usage is standard, but trailing edge region experiences inadequate cooling leading to thermal damage and erosion
Solution Approach 1:
The cooling passages are nested within the airfoil structure, with serpentine passages routed through the blade interior and terminating at the trailing edge. This nesting allows efficient use of the blade's internal volume for cooling while delivering cooling air directly to the most thermally stressed region.
Solution Approach 2:
The cooling passages extend into the trailing edge region, utilizing the depth dimension of the blade structure. This three-dimensional cooling approach delivers cooling air directly to the trailing edge face, providing effective thermal protection to the thinnest and most vulnerable portion of the airfoil.
3Strength
If platform structure without undercuts is maintained, then structural integrity is simpler, but stress concentration at trailing edge leads to crack initiation from pedestals
Solution Approach 1:
The undercut configuration introduces asymmetry in the platform geometry, with the first undercut extending from the pressure side and the second undercut extending from the suction side. This asymmetric design creates optimized stress distribution patterns that prevent stress concentration at the trailing edge pedestals, eliminating the primary location for crack initiation.
Solution Approach 2:
The undercut surfaces are configured with curved transitions rather than sharp angles, creating smooth stress flow paths. The rounded geometry of the undercut surfaces prevents stress concentration by distributing mechanical loads more evenly across the platform-trailing edge interface, thereby preventing crack initiation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed solution effectively reduces trailing edge stresses by 37% and operating temperatures by 4.8%, resulting in a 769% improvement in design life, specifically addressing the issues of stress and temperature management in gas turbine blades.
Implementation Method 1
Cooling air is then ejected through a plurality of slots in the trailing edge. Actively cooling this region is necessary because the trailing edge is the thinnest portion of the airfoil and most subject to erosion and thermal damage
Implementation Method 2
turbine blade having one or more undercuts formed in the platform to relieve mechanical and thermal stresses in the airfoil trailing edge
Data Source
AI summary
A system and method of extending the useable life of a gas turbine blade is disclosed in which the gas turbine blade includes an undercut configuration designed to relieve mechanical and thermal stress imparted into the pedestal region of the airfoil trailing edge. The embodiments of the present invention include turbine blade configurations having different trailing edge undercut configurations as well as additional cooling supplied to the internal passages of the trailing edge region of the turbine blade.