Gas Turbine Securing Ring Asymmetric Undercut Design
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Solution Overview
Problem
Existing gas turbines face challenges in securely locking guide vane assemblies to prevent them from falling out, especially under conditions like vibration and shaft breakage, where the securing ring may undesirably lift out of its groove.
Innovation Solution
A securing ring with a traversing radial slot featuring an undercut portion and radially inner rim section, allowing for axial locking and easy removal, is designed to prevent expulsion by forming angles that facilitate mechanical self-locking and enable secure engagement with a hook-type tool.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the securing ring is inserted into the circumferential groove to axially lock the guide vane assembly, then the guide vane assembly is secured against falling out, but the securing ring may undesirably lift out of the groove during operation due to vibration and other forces
Solution Approach 1:
The slot in the securing ring is designed with an asymmetric undercut portion on only one flank (the first flank), creating an asymmetric geometry that provides mechanical self-locking. The undercut portion with its specific angle (at least 85°) relative to the radially outer rim creates a geometric lock that prevents the securing ring from lifting out radially while still allowing controlled removal with a tool.
Solution Approach 2:
The undercut portion is designed to preemptively counteract the lifting forces that arise during operation. By creating a geometric feature that physically blocks radial displacement before it can occur, the design prevents the harmful effect of vibration-induced lifting rather than reacting to it after it happens.
2Ease of manufacture
If the securing ring has a traversing slot for elastic deformation during insertion, then the securing ring can be inserted into the groove, but the slot structure may allow the securing ring to be accidentally removed from the groove
Solution Approach 1:
The asymmetric undercut portion creates a directional feature that allows easy insertion (by deforming the slot) but prevents accidental removal. The undercut geometry acts as a one-way mechanism: it offers no resistance during insertion when the slot is elastically deformed, but creates a mechanical lock during operation that prevents unintended removal.
Solution Approach 2:
The undercut portion acts as an intermediary feature between the slot structure and the securing ring's retention function. It mediates between the need for easy insertion (via slot deformation) and the need for secure retention, providing a geometric feature that enables controlled removal only with the appropriate tool while preventing accidental loss.
3Ease of manufacture
If the securing ring is designed with a simple circular cross-section, then the manufacturing is simpler, but the removal of the securing ring from the groove requires excessive force and may damage components
Solution Approach 1:
The securing ring is segmented by the traversing slot that extends through its circumference, dividing the ring structure into two flexible halves. This segmentation allows the ring to be elastically deformed during insertion and removal, enabling controlled extraction without excessive force while maintaining a relatively simple overall circular cross-section for easy manufacturing.
Solution Approach 2:
The asymmetric undercut portion creates a preferential direction for removal by providing a hook-type engagement feature. This asymmetric geometry allows removal tools to engage effectively and extract the securing ring with controlled force, while the overall simple circular cross-section remains easy to manufacture.
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 guide vane assemblies against falling out and minimizes the risk of undesired lifting during operation, ensuring reliable operation and maintenance by allowing for easy removal and reinstallation.
Implementation Method 1
To insert the securing ring into the circumferential groove, it is elastically deformed. To this end, it has a traversing slot, whose clearance width is reduced by this elastic deformation, it being possible for the radial end faces to overlap.
Data Source
AI summary
A gas turbine having a guide vane assembly (2) and a securing ring (1) for axially locking the guide vane assembly in position that has a radially outer rim (1A) which is configured in a housing-side groove (3.1), a radially inner rim (1B) which is configured outside of the groove, and a slot (10) which extends from the radially outer rim to the radially inner rim, and a first flank having a radially inner rim section (12) and an undercut portion (11), the radially inner rim section forming an angle (α) of at least 50° with the radially inner rim.