Turbine Blade Dovetail Insert for Re-Machined Rotor Grooves
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Solution Overview
Problem
Existing turbine blade assemblies face challenges in fitting new blades into enlarged rotor grooves without increasing weight, which can lead to increased centrifugal forces and stresses, especially during servicing when the groove depth varies.
Innovation Solution
A turbine blade assembly with a dovetail that includes a separate extension insert with positioning legs and a fixation element, allowing for customizable fitting into various groove depths and widths, reducing the need for precise manufacturing and minimizing additional weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the rotor groove is re-machined to remove damaged material, then the rotor lifespan is increased, but the rotor groove depth increases requiring a heavier dovetail that increases centrifugal forces and stresses
Solution Approach 1:
The dovetail is divided into two separate components: the original blade dovetail and a removable extension insert. This segmentation allows the extension insert to fill the additional depth created by re-machining without requiring the entire dovetail structure to be heavier, thus maintaining lower centrifugal forces while accommodating the enlarged groove.
Solution Approach 2:
The extension insert acts as an intermediary element between the blade dovetail and the re-machined rotor groove. It fills the additional depth created by material removal, enabling the original lighter dovetail to fit into the enlarged groove without increasing overall weight or centrifugal stresses.
2Reliability
If the rotor groove is re-machined deeper, then damaged material is removed to eliminate cracks, but the new blade dovetail must fit the larger groove which complicates manufacturing
Solution Approach 1:
By segmenting the dovetail into a permanent portion (original blade dovetail) and a variable portion (removable extension insert), the manufacturing process becomes more flexible. The extension insert can be separately manufactured to match specific groove depths, making it easier to accommodate re-machining variations without redesigning the entire dovetail.
Solution Approach 2:
The solution introduces adaptability through the removable extension insert, which can be configured with different lengths and geometries depending on the specific re-machining requirements. This dynamic approach allows the assembly to adapt to varying groove depths while maintaining standardization of the core blade dovetail design.
3Shape
If a heavier dovetail is used to fill the enlarged rotor groove, then the groove is properly filled, but the blade weight increases causing higher centrifugal forces
Solution Approach 1:
The dovetail is segmented into the original blade dovetail (maintaining original weight) and a separate extension insert (adding minimal weight only where needed). This allows the groove to be properly filled for structural integrity while minimizing additional weight by only adding material in the extended region, not throughout the entire dovetail structure.
Solution Approach 2:
The extension insert provides localized material only in the specific region where the groove has been deepened, rather than increasing the weight of the entire dovetail. This local addition of material maintains proper groove filling for structural support while minimizing the overall weight increase of the moving blade assembly.
Data Source
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AI summary
A turbine blade assembly (400) for a rotor groove (410) is disclosed. A dovetail (404) of the turbine blade (402) includes a mounting arm (420) and an end surface (422) facing radially inward relative to the rotor axis. An extension insert (406) includes a first end (424) configured to contact the end surface (422) of the dovetail (404) and a second end (426). At least one positioning leg (428) extends radially inward relative to the axis from the second end (426) of the insert (406). The dovetail (404) and the extension insert (406) are configured to be positioned in the rotor groove (410) to mount the turbine blade (402) to the rotor (412). The mounting arm (420) engages a radially inward facing rotor hook (420) of the rotor groove (410) and positioning leg(s) (428) engage one of a radially outward facing surface (432) of the rotor groove (410) and a planar plate shim (440) between the positioning leg(s) (428) and the radially outward facing surface (432) of the rotor groove (410).