Two-Stage Gas Turbine Shroud Retention for Thermal Growth
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Solution Overview
Problem
Maintaining a consistent tip clearance in gas turbine engines is challenging due to differential thermal expansion rates between shroud materials and surrounding components, leading to wear and positioning issues.
Innovation Solution
A shroud system with a support structure and a spring and retainer system that allows for relative radial movement between shrouds and the support structure, using load transfer pins and springs to maintain continuous contact and control the shroud's position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a shroud is rigidly coupled to the support structure, then positioning precision is improved, but thermal stress and wear increase due to differential thermal expansion
Solution Approach 1:
The shroud coupling system transitions from a rigid static connection to a dynamic adjustable connection. The spring mechanism allows the shroud to move radially relative to the support structure, accommodating differential thermal expansion while maintaining controlled contact. This dynamic system absorbs thermal stresses and prevents excessive wear by allowing controlled movement rather than rigid constraint.
Solution Approach 2:
The system changes the physical state of the coupling from rigid to compliant by introducing a spring element. The spring constant and pre-load parameters are selected to provide sufficient positioning force while allowing thermal expansion accommodation. This parameter adjustment enables the system to maintain positioning precision without transmitting excessive thermal stresses to the shroud.
2Object-affected harmful factors
If a spring mechanism is introduced to accommodate thermal expansion, then wear is reduced, but device complexity increases
Solution Approach 1:
The coupling mechanism is segmented into distinct functional elements: the spring component, the shroud, and the support structure. This segmentation allows each component to perform its specific function - the spring absorbs thermal expansion differences, the shroud maintains positioning, and the support structure provides stability. The modular design simplifies manufacturing and maintenance while reducing overall system complexity.
Solution Approach 2:
The spring acts as an intermediary element between the rigid support structure and the shroud. It mediates the interaction between these two components by absorbing differential thermal expansion and maintaining controlled contact. This intermediary function reduces wear on the shroud while preventing the need for complex active control systems.
3Object-affected harmful factors
If the shroud is allowed to move radially to accommodate thermal growth, then thermal stress is reduced, but tip clearance control becomes more challenging
Solution Approach 1:
The spring mechanism provides passive feedback control for tip clearance. As the shroud expands thermally, the spring compresses proportionally, automatically adjusting the shroud position to maintain consistent tip clearance. This feedback mechanism eliminates the need for active control systems while maintaining precision tip clearance control throughout the thermal cycle.
Solution Approach 2:
The system explicitly utilizes thermal expansion principles by designing the spring pre-load and stiffness to compensate for the differential thermal expansion between the shroud and support structure. The spring is calibrated to maintain optimal contact force and positioning across the operating temperature range, ensuring consistent tip clearance control despite thermal growth.
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 system effectively maintains a consistent tip clearance and reduces wear on shrouds by accommodating thermal growth differences, ensuring precise alignment and minimizing radial movement.
Implementation Method 1
A spring is coupled to the support structure and engages both load transfer pins. The spring applies forces on the load transfer pins toward their respective shroud.
Implementation Method 2
the shrouds may react to thermal excursions by expanding or growing radially at a different rate than surrounding components
Data Source
AI summary
A shroud system for a gas turbine engine. The shroud system includes a support structure defining two stages. One shroud is disposed at one stage and another shroud is disposed at the other stage. A retention and positioning assembly is disposed on the support structure and positions and holds both shrouds relative to the support structure. A load transfer pin is located radially outward from each of the shrouds. A spring is coupled to the support structure and engages both load transfer pins. The spring applies forces on the load transfer pins toward their respective shroud. A retainer is coupled with the support structure and extends over both stages.