Turbine Blade Root Profile with Segmented Lobes
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Solution Overview
Problem
Turbine blade roots in gas turbine engines face challenges in securely attaching to rotor slots due to centrifugal forces, thermal expansion, and bending stresses, while existing firtree-shaped root geometries may not adequately address these issues.
Innovation Solution
A turbine blade root design featuring three lobes with specific geometric configurations, including varying lengths, tooth heights, and radii, along with a cooling passage, to enhance attachment security and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a firtree-shaped root geometry is used, then the attachment security is improved, but the ability to withstand thermal expansion and bending stresses deteriorates
Solution Approach 1:
The root geometry is segmented into three distinct lobes with varying lengths and tooth heights, allowing each segment to independently respond to different stress conditions. The first lobe (longest) primarily handles centrifugal forces, the second lobe (intermediate) addresses bending stresses, and the third lobe (shortest) accommodates thermal expansion, thereby resolving the contradiction between attachment security and stress resistance.
Solution Approach 2:
Different regions of the root are given different geometric properties - the lobes have varying lengths, tooth heights, and contact point distributions. This local differentiation allows optimal performance at each contact point with the rotor slot, enabling the root to simultaneously achieve secure attachment and withstand multiple types of stresses through localized geometric optimization.
2Reliability
If the root geometry is optimized for centrifugal forces, then attachment security is improved, but adaptability to different stress conditions deteriorates
Solution Approach 1:
The root employs asymmetric geometry with three lobes of different lengths and tooth heights, breaking the symmetry of conventional firtree designs. This asymmetry allows each lobe to be specifically tailored for different stress conditions - the longest first lobe for centrifugal forces, the intermediate second lobe for bending stresses, and the shortest third lobe for thermal expansion, thereby achieving both secure attachment and high adaptability to multiple stress factors.
Solution Approach 2:
The invention adds dimensional complexity by varying lobes in multiple parameters (length, tooth height, contact point position) rather than relying on a single geometric modification. This multi-dimensional geometric variation enables the root to adapt to different stress conditions while maintaining secure attachment, resolving the contradiction between reliability and adaptability.
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 design provides a secure attachment of the turbine blade root to the rotor slot, effectively withstanding centrifugal forces, thermal expansion, and bending stresses, thereby improving the overall performance and reliability of the gas turbine engine.
Implementation Method 1
a cooling passage that extends from the terminal end in the radial direction from the root into the airfoil
Implementation Method 2
Root profiles must accommodate many factors, such as centrifugal forces, thermal expansion, and bending stresses
Implementation Method 3
Root profiles must accommodate many factors, such as centrifugal forces, thermal expansion, and bending stresses
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A turbine blade for a gas turbine engine includes an airfoil that extends in a first radial direction from a platform. A root extends from the platform in a second radial direction and has opposing lateral sides that provide a firtree-shaped contour. The contour includes first, second and third lobes on each of the lateral sides and that tapers relative to the radial direction away from the platform. The first, second and third lobes each provide contact surfaces arranged at about 45° relative to the radial direction. A contact plane on each lateral side at an angle of about 11° relative to the radial direction defining a contact point on each of the contact surfaces. The first, second and third lobes each include first, second and third grooves that are substantially aligned with one another along an offset plane spaced a uniform offset distance from the contact plane.