Gas Turbine Guide Blade Trailing Edge Cooling and Stress Relief
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Solution Overview
Problem
The thin trailing edge of guide vanes in gas turbines, due to integrated cooling slots, is prone to mechanical stress and reduced service life from thermal loads, leading to potential cracks at the connection point with the inner platform.
Innovation Solution
A keyhole-shaped slot is introduced on the inner platform, parallel to the platform's plane, with a parallel-sided wall section and a circular end section, decoupling the vane tip from the trailing edge to reduce thermal stresses without increasing material thickness, and the cooling slot intersects one corner of a quadrangular blade head, forming an acute angle with the side walls to balance stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a cooling slot is integrated into the airfoil to cool the trailing edge, then cooling effectiveness is improved, but the trailing edge thickness is reduced leading to increased mechanical stress and reduced service life
Solution Approach 1:
The trailing edge region is segmented into multiple cooling slots distributed along the trailing edge, rather than using a single large cooling slot. This segmentation allows the cooling function to be distributed while maintaining structural integrity of the trailing edge, as each smaller slot removes less material and maintains adequate wall thickness for mechanical strength.
Solution Approach 2:
The cooling slots are positioned specifically in regions where cooling is most needed (near the trailing edge), while the root region and other areas maintain sufficient material thickness for structural strength. This local differentiation of cooling intensity allows optimal balance between thermal management and mechanical strength.
2Productivity
If the trailing edge is made thin to accommodate the cooling slot, then cooling performance is improved, but resistance to mechanical loads and thermal stresses is reduced
Solution Approach 1:
Multiple smaller cooling slots are distributed along the trailing edge instead of one large slot, maintaining adequate material between slots to resist mechanical loads and thermal stresses while still providing effective cooling through the trailing edge region.
Solution Approach 2:
The design anticipates thermal and mechanical loads by maintaining sufficient material thickness in critical regions and positioning cooling slots to avoid high-stress concentration areas, thereby preventing cracks and extending service life before failures can occur.
3Temperature
If cooling slots are provided on the pressure side parallel to the trailing edge, then trailing edge cooling is achieved, but the blade geometry becomes more complex and manufacturing more difficult
Solution Approach 1:
The cooling slots are designed to serve multiple functions: they provide trailing edge cooling, act as stress relief features, and can be integrated with the existing blade manufacturing processes. The slot geometry and positioning are optimized to achieve cooling effectiveness while maintaining compatibility with standard casting or machining processes.
Solution Approach 2:
The cooling slot parameters (width, depth, spacing, orientation) are optimized to achieve effective cooling with minimal impact on blade geometry. By carefully controlling these parameters, the design achieves cooling performance while keeping manufacturing complexity manageable through standardized slot configurations.
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
This design enhances the service life of guide vanes by reducing thermal stresses and mechanical loads on the thin trailing edge, preventing cracks and extending the vane's operational lifespan without altering the geometry or material thickness.
Implementation Method 1
a gaseous cooling medium (e.g. compressed air from the compressor of the gas turbine is discharged or steam is supplied. In all cases, the cooling medium is sent through cooling channels (often running in serpentines) formed in the blade and/or through corresponding openings (bores, slits) to the outside in order to form a cooling film (film cooling), in particular on the outside of the blade.
Data Source
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AI summary
A guide blade (20) for a gas turbine (10), in particular for the low-pressure turbine (18) of a gas turbine (10) with sequential combustion, has an aerofoil (22) extending in a radial direction between a blade head (23) and a shroud (21), wherein the aerofoil (22) extends transversely to the direction of the hot gas flow (30) between a leading edge (27) and a trailing edge (28) and has a pressure side (31) and a suction side, and wherein a cooling slit (29) running parallel to the trailing edge (28) is provided upstream of the trailing edge (28) on the pressure side (31) and allows a cooling medium to emerge from the guide blade (20) over the entire length of said guide blade (20) and cool the trailing edge (28) thereof. With such a guide blade, the service life is extended by means (33) for reducing thermal stresses being provided on the blade head (23) underneath the trailing edge (28) and the cooling slit (29).