Turbine Blade Locking Set with Segmented Elements
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Solution Overview
Problem
Conventional methods for securing turbine blades on rotor disks are prone to structural weakening and require complex machining and assembly processes, with friction-based solutions being unreliable due to assembly and operating condition dependencies.
Innovation Solution
A fixing set comprising a root portion with a dovetail connection and three locking elements that are inserted into the groove between the root portion and the disk, allowing easy assembly and irreversible locking without additional machining, using a first locking element to engage the root portion and groove, a second element to be pulled back and retained by a third element, preventing reversibility through plastic deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional locking methods (tab washers, wedge shaped elements, threads) are used to securely lock the blade to the rotor disk, then the blade is locked on the rotor disk by friction or mechanical engagement, but the special machining needed introduces discontinuities on the groove surface which turn into stress concentration regions and cause structural weakening
Solution Approach 1:
The locking function is divided into multiple locking elements (first locking element, second locking element, third locking element) that are inserted into the groove, distributing the locking function across separate components rather than requiring complex machining of the groove itself. This segmentation allows the groove to remain continuous and structurally sound while achieving reliable blade locking through the distributed locking elements.
Solution Approach 2:
Locking elements serve as intermediary components between the blade root portion and the groove, providing the locking function without requiring direct complex machining of the groove. These intermediary elements (particularly the wedge-shaped second and third locking elements) transmit and amplify forces to secure the blade while preserving the structural integrity of the groove.
2Reliability
If threads are present on the rotor groove to enable locking, then mechanical engagement is achieved, but caulking operations become troublesome due to strict assembling requirements and threads may turn into crack initializations
Solution Approach 1:
The threading function is extracted from the groove itself and transferred to separate locking elements. The groove remains a simple, continuous receptacle without threads or complex features, while the locking elements (particularly the second and third elements with their threaded pins) provide the mechanical engagement function externally, simplifying groove machining and assembly.
Solution Approach 2:
The locking elements, particularly the second and third locking elements with threaded pins, serve as sacrificial or replaceable components that can be easily installed and removed. These elements absorb the complexity of threading and caulking operations, allowing the main groove structure to remain simple and the assembly process to be less stringent.
3Reliability
If friction-based or interference-based retaining methods are applied to the coupling between the blade root and groove, then locking is achieved, but these methods depend heavily on assembly and operating conditions and therefore cannot always be employed
Solution Approach 1:
The locking elements are pre-configured with specific geometries (wedge shapes, threaded pins, cam surfaces) that automatically generate the necessary locking forces upon insertion. The second locking element, for example, is forced into the groove between the root portion and groove, and its wedge shape automatically generates radial thrust action that locks the blade without depending on specific friction conditions or assembly forces.
Solution Approach 2:
The locking mechanism transitions from relying on friction coefficients and interference fits (which are sensitive to assembly conditions) to using geometric parameters of the locking elements. The wedge angle, pin thread geometry, and cam surface profiles are designed to generate deterministic locking forces that are independent of assembly speed, friction conditions, or operating temperature variations.
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 securely and reliably fixes turbine blades on rotor disks within a small tolerance range, eliminating the need for extra machining and ensuring stability during high-speed rotation, overcoming the drawbacks of conventional methods by providing a simple and effective locking mechanism.
Implementation Method 1
the second element is retained in position due to the plastic deformation or change of shape and geometry of the second element thus preventing any reversibility of assembly
Data Source
AI summary
Fixing set for securely assembling and locking a blade shaped element, for instance a turbine blade, on a support, for instance a turbine rotor. The blade shaped element is adapted to be inserted into a groove of the external surface of the support and the fixing set includes first, second and third locking elements adapted to be inserted into the groove, between the lower end surface of the root portion of the blade shaped element and the groove base surface. The first, second and third locking elements are adapted to securely lock the blade shaped element on the support and are further adapted to allow easy and simple installation by an operator with no need of additional working and extra machining.