Turbine Movable Ring Assembly Thermal Stress Reduction
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Solution Overview
Problem
Turbine engine turbines face reduced lifespan due to the 'flange opening' phenomenon caused by high thermal gradients between the outer and inner annular portions of movable rings, leading to mechanical stress and deformation.
Innovation Solution
A movable ring assembly is designed with a fixing ferrule and a movable ring that includes radial sealing members, a seal between the ring and the ferrule, and anti-rotation features like slots and lugs, which dissociates the outer annular portion from the bolted connection, reducing thermal exposure and mechanical stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the movable ring is fixed between the upstream disk and downstream disk with bolted connections, then the sealing function is ensured, but the flange opening phenomenon occurs due to thermal gradient causing reduced lifespan
Solution Approach 1:
The movable ring assembly is divided into separate functional components: the movable ring itself, the fixing ferrule, and the bolted connection system. This segmentation allows the movable ring to be isolated from the thermal stress experienced by the bolted connection, enabling the sealing function to be maintained while preventing thermal gradient-induced damage to the flanges.
Solution Approach 2:
The fixing ferrule acts as an intermediary element between the movable ring and the bolted connection. It provides a thermal barrier that protects the bolted connection from direct exposure to high temperatures, thereby preventing flange opening while maintaining the structural integrity needed for sealing.
2Reliability
If the movable ring is exposed to hot air flow stream, then the sealing function is achieved, but high thermal gradient causes strong forces at fixing flanges leading to flange opening
Solution Approach 1:
The assembly is segmented into thermal zones: the movable ring operates in the high-temperature zone maintaining sealing, while the fixing ferrule and bolted connection are positioned in cooler zones, reducing thermal expansion forces at the flanges.
Solution Approach 2:
The fixing ferrule serves as a thermal intermediary, absorbing and dissipating heat away from the bolted connection, thereby reducing the mechanical forces generated by thermal expansion at the fixing flanges.
3Strength
If the movable ring is directly connected to bolted connection, then structural support is provided, but thermal exposure causes deformation and creeping of the movable ring
Solution Approach 1:
The structural support function is separated from the thermal exposure zone by introducing the fixing ferrule as an intermediate support structure. This allows the movable ring to maintain its dimensional stability while still receiving structural support through the thermally isolated ferrule connection.
Solution Approach 2:
The fixing ferrule acts as a structural intermediary that provides support to the movable ring while being thermally isolated from it, preventing heat transfer that would cause deformation and creeping of the movable ring.
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 significantly increases the lifespan of turbine engine turbines by reducing mechanical forces on flanges, maintaining sealing and ventilation, and ensuring retention of retaining rings, while simplifying maintenance.
Implementation Method 1
a seal (46) interposed between the movable ring (42) and the ferrule (44)
Implementation Method 2
The radial sealing members 32 of each movable ring 28 cooperate with the annular inner surface of the fixed blade 12 facing said ring 28 and thus ensure sealing between the upstream cavity and the downstream cavity of the turbine
Implementation Method 3
The ferrule (44) comprises at least one cooling lunule (43) above the bolted connection (26)... These cooling lunules (43) allow a circulation of cool air collected upstream of the turbine and circulating through each bolted connection (26). This cool air circulating from upstream of the turbine is able to pass through the lunule (43) to the air diffusion cavity (60) before diffusing into each socket (18) of the disk (20b) to ventilate them
Implementation Method 4
The outer annular portion of the movable ring 28 is subjected to very high temperatures due to the flow stream of hot air 14. The result is a high thermal gradient between the outer annular portion of the rings 28 and their inner annular portion
Implementation Method 5
The vertical arrow illustrates the orientation and the direction of the mechanical forces resulting from the thermal gradient in the movable ring 28 which is deforming
Data Source
AI summary
A movable ring assembly (4) for a turbine engine turbine (10) that is mounted between two successive rotor discs (20a) and (20b) of said turbine (10), said rotor discs (20a) and (20b) being fixed to each other by bolting, characterised in that it comprises:—a fixing ferrule (44) fixed between the upstream (20a) and downstream (20b) discs by the bolting thereof; a part forming a movable ring (42), said part supporting radial sealing members (32) and being fixed between the upstream disc (20a) and the ferrule (44);—and a seal (46) interposed between said part forming the movable ring (42) and the ferrule (44).