Gas Turbine Rotor Blade Fir Tree Spring Load Distribution
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Solution Overview
Problem
Gas turbine rotor blades face high thermomechanical loads due to increasing efficiency demands, with blade roots and turbine disk grooves being the limiting factors, and existing methods for reducing these loads, such as flattening fir tree springs, are inefficient and require high accuracy.
Innovation Solution
The azimuthal extent of lateral tooth extensions on the fir tree spring is reduced in areas experiencing high pressure and compressive loads during operation, allowing for a more even distribution of loads and extending the service life of the components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the azimuthal extent of lateral tooth extensions is reduced in high pressure load areas, then pressure load distribution is improved and service life is extended, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by reducing the azimuthal extent of lateral tooth extensions specifically in axial regions where pressure loads exceed a predetermined threshold, while maintaining the original geometry in low-load areas. This localized modification optimizes the tooth extension geometry according to the actual load distribution, improving reliability without requiring complete redesign of the entire tooth structure.
Solution Approach 2:
The patent changes the geometric parameter (azimuthal extent) of the lateral tooth extensions in specific axial regions. By modifying this dimensionality parameter based on pressure load distribution, the design achieves better load sharing while controlling manufacturing complexity through targeted changes rather than comprehensive redesign.
2Stress or pressure
If flattening of fir tree spring is performed to reduce loads, then pressure distribution is improved, but manufacturing effort and accuracy requirements increase significantly
Solution Approach 1:
Instead of uniformly flattening the entire fir tree spring, the patent applies local modifications only to specific lateral tooth extensions in high-pressure axial regions. This selective approach reduces manufacturing effort and accuracy requirements compared to comprehensive flattening, while still achieving improved pressure distribution where it is most needed.
Solution Approach 2:
The patent segments the fir tree spring into multiple lateral tooth extensions, and further segments each extension into different axial regions with different azimuthal extents. This segmentation allows independent optimization of each segment based on its specific load characteristics, making the overall manufacturing process more manageable and less demanding in terms of precision.
3Force
If the azimuthal extent of lateral tooth extensions is reduced, then force distribution is shifted to less loaded regions, but the gap between tooth area and lateral groove wall must be controlled
Solution Approach 1:
The patent changes the azimuthal extent parameter of lateral tooth extensions in high-load axial regions, which indirectly controls the gap geometry between the tooth area and lateral groove wall. By optimizing this dimensional parameter, the design achieves better force distribution while the gap geometry self-adjusts to maintain appropriate clearance for load transfer.
Data Source
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AI summary
Disclosed is a rotor blade (1) for a gas turbine (100), said rotor blade comprising an aerofoil (2) having a pressure side (10) and an intake side (12) which transition into a platform (14) to which an attachment region (16) is connected, said region having a fir tree spring (18) which has a plurality of lateral toothed extensions (20, 22, 24, 26, 28, 30) arranged on the pressure side (10) and the intake side (12), which extensions extend in an azimuthal direction. Said rotor blade should enable increased efficiency at the same time as an increased service life of the gas turbine and its components to be achieved. In addition, the azimuthal extent of one lateral toothed extension (20, 22, 24) is reduced in an axial region of said lateral toothed extension (20, 22, 24), in which region the pressure load during operation exceeds a predefined threshold.