Turbine Blade Root Securing Device with Power Spring
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Solution Overview
Problem
Turbine blades in turbomachines face challenges such as high centrifugal forces, vibration loads, corrosion, and difficulty in maintaining secure attachment due to metal wedges, which lead to mechanical damage and material fatigue, especially during prolonged operation in steam environments.
Innovation Solution
A rotor with a securing device featuring a holding piece and power spring that prevents axial displacement of the turbine blade root, distributing forces better and using a metal sheet to prevent axial shifting, ensuring secure and precise mounting over long periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal wedges are used to lock the turbine blade root in the blade groove, then axial and radial locking is achieved, but sufficient holding forces cannot be generated in the radial direction for large rotor blades and corrosion occurs during prolonged operation
Solution Approach 1:
The securing device is divided into multiple functional components: a holding piece with projection for axial positioning, a power spring for radial force generation, and a metal sheet for additional axial restraint. This segmentation allows each component to specialize in providing specific forces, enabling the system to generate sufficient radial holding forces while maintaining axial locking reliability.
Solution Approach 2:
The power spring introduces a dynamic, elastic element that can adapt to varying operational conditions. The spring continuously exerts radial force on the holding piece, allowing the securing device to maintain reliable attachment even as thermal and mechanical conditions change during prolonged operation, while avoiding the corrosion issues of rigid metal wedges.
2Reliability
If metal wedges are used to secure the turbine blade, then locking is achieved, but corrosive behavior occurs during prolonged operation in steam medium making disassembly difficult
Solution Approach 1:
The power spring acts as an intermediary element between the holding piece and the blade root, providing the necessary radial force without direct metal-to-metal contact in the corrosive steam environment. This reduces corrosion of critical securing components while maintaining reliable attachment.
Solution Approach 2:
The securing device combines different material properties: the holding piece and metal sheet provide structural integrity and positioning, while the power spring provides elastic radial force. This composite approach allows selection of materials optimized for different functions, with the spring potentially using corrosion-resistant materials to withstand the steam environment.
3Reliability
If superimposed notches are used in axial locks, then axial positioning is achieved, but increased stress occurs leading to limited applicability
Solution Approach 1:
The solution moves from a two-notch axial locking system to a three-dimensional securing mechanism involving the holding piece projection in a recess, power spring radial force, and metal sheet axial restraint. This dimensional expansion distributes stresses more effectively while maintaining axial positioning reliability.
Solution Approach 2:
The holding piece projection is specifically designed to engage with a recess in the blade root, creating a localized, precise axial positioning feature. This concentrated geometric engagement provides reliable axial positioning without the stress concentration issues of superimposed notches, as the projection-recess interface distributes loads more effectively.
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 solution effectively secures turbine blades by distributing forces and minimizing axial displacement, reducing mechanical damage and material fatigue, while maintaining secure attachment even at low rotational speeds and high centrifugal forces.
Implementation Method 1
the securing means comprises a power spring which exerts a force acting in the radial direction from the rotor to the turbine blade
Implementation Method 2
the holding piece having a projection which is arranged in a recess in the turbine blade root, the projection engaging in the recess in such a way that displacement of the holding piece in the axial direction is prevented
Implementation Method 3
the safety device has a metal sheet which is arranged in a second recess in the holding piece and in a rotor recess, the metal sheet engaging in the second recess and in the rotor recess in such a way that the metal sheet is prevented from shifting in the axial direction
Implementation Method 4
the rotating blades arranged on the rotor are exposed to high centrifugal forces. The turbine blade root of the turbine blades must therefore withstand high forces and is pushed radially outwards in the blade groove
Data Source
Figure 1~2
Figure 3~5
Figure 6~8
AI summary
The invention relates to a securing device (2) for a turbine blade; said securing device (2) prevents the turbine blade from moving radially and axially and is characterized by a retaining piece (10) that includes a projection (15) which extends into a recess (17) in the root (3) of the turbine blade and which prevents the blade from moving axially.