Turbomachine Stator Actuation Ring Automatic Centering
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Solution Overview
Problem
Conventional turbomachine stator designs with variable-pitch stator vanes face challenges in achieving and maintaining centering due to differential expansion and temperature effects, leading to off-centering issues and increased operational complexity.
Innovation Solution
A compact system with a coaxial rail and radially moving rollers ensures automatic centering of the actuation ring, eliminating the need for functional clearance and reducing operational forces, utilizing a radial guide arrangement and rolling bearings for precise alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional centering pads with adjustments are used to position the actuation ring around the casing, then initial centering can be achieved, but functional clearance must be restored to accommodate thermal expansion, resulting in off-centering during operation
Solution Approach 1:
The invention replaces static centering pads with dynamic rollers that can move radially along the coaxial rail. This allows the centering mechanism to adapt automatically to thermal expansion and contraction, maintaining continuous contact and centering without requiring functional clearance. The rollers move in response to dimensional changes, preserving centering precision across temperature variations.
Solution Approach 2:
The radial guide arrangement enables the rollers to self-adjust their position automatically in response to thermal expansion. The system uses the expansion forces themselves to drive the rollers along the rail, maintaining centering without external adjustment mechanisms. The crown and casing expand together, and the rollers accommodate this expansion while preserving coaxial alignment.
2Reliability
If functional clearance is provided to accommodate thermal expansion between the crown and casing, then operational reliability is improved, but centering precision deteriorates due to off-centering
Solution Approach 1:
The rollers provide dynamic accommodation of thermal expansion through radial movement along the rail, eliminating the need for static functional clearance. The system transitions from a rigid clearance-based design to a flexible, movement-based design that maintains precision while accommodating operational changes.
Solution Approach 2:
The invention changes the operational parameter from fixed clearance to variable roller position. The rollers can change their radial position along the rail in response to temperature changes, allowing the system to adapt to parameter changes (thermal expansion) without compromising the centering precision that would be lost with fixed clearance.
3Ease of manufacture
If radially adjustable centering pads are used to ensure coaxiality, then assembly is possible, but adjustments are difficult and time-consuming
Solution Approach 1:
The radial guide arrangement with rollers eliminates the need for manual adjustment during assembly. The rollers are guided radially by the radial guide arrangement, which automatically positions them correctly as the crown is assembled to the casing. This self-positioning mechanism removes the time-consuming adjustment step entirely.
Solution Approach 2:
The invention extracts the adjustment function from the centering mechanism. Instead of requiring manual adjustment of pad positions, the system uses the radial guide arrangement to automatically establish correct positions. The adjustment complexity is removed from the assembly process.
4Reliability
If heavy-duty centering mechanisms are used to maintain centering under operational forces, then centering stability is improved, but device complexity and mass increase
Solution Approach 1:
The invention transitions from sliding friction (pad-on-boss) to rolling contact (roller-on-rail). This phase transition in the type of contact dramatically reduces friction and operational forces, allowing a simpler, lighter mechanism to achieve the same centering stability. The rolling motion naturally accommodates misalignment and thermal expansion.
Solution Approach 2:
The invention replaces the complex adjustable pad mechanism with a simpler roller-based system guided by a radial guide arrangement. The coaxial rail provides the guiding function, eliminating the need for complex adjustment mechanisms while maintaining or improving centering stability through the inherent guidance of the rail-roller system.
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 provides a lightweight, perfectly centered actuation ring with simplified assembly and maintenance, maintaining initial centering quality across varying temperatures and materials, while reducing operational forces and avoiding misalignment.
Implementation Method 1
at least three groups of circumferentially spaced rollers are subject to move along said rail, each group of rollers being coupled to said crown by a radial guide arrangement
Implementation Method 2
each roller being rotatably mounted on a radial axis... utilizing a radial guide arrangement and rolling bearings for precise alignment
Implementation Method 3
each group of rollers is coupled to said crown by a radial guide arrangement (i.e. each group of rollers is guided radially with respect to the crown)
Implementation Method 4
to facilitate the sliding of the shaft in the bore, there is provided, between the bore and the shaft, a plain bearing or a rolling bearing
Implementation Method 5
Advantageously, to facilitate the sliding of the shaft in the bore, there is provided, between the bore and the shaft, a plain bearing or a rolling bearing
Implementation Method 6
to take into account the expansion phenomena which occur during operation and which involve changes in distinct dimensions for the crown and the crankcase. The crown and the casing have, in fact, different coefficients of expansion
Data Source
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AI summary
The stator comprises a housing and at least one stage of variable-pitch rectifier blades (12), said blades being moved by an actuating ring (18) external to said housing and carried by said housing and said ring being connected by connecting rods (16) to the blades of said stage to actuate them simultaneously, in which the housing comprises a fixed coaxial rail (24) projecting from the external surface of the housing, and at least three circumferentially spaced groups of rollers (26) are constrained to move along said rail, each group of rollers being coupled to said ring (18) by a radial guide arrangement, each group of rollers (26) comprising at least two rollers (34) engaged with said rail (24), and each roller being mounted for rotation on a radially oriented shaft (36), this shaft being mounted directly on said ring (18).