Hydrostatic Seal Carrier Arm for Thermal Growth Compliance
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Solution Overview
Problem
Gas turbine engines face challenges in maintaining efficient sealing between rotating and static components due to thermal stresses and leakage issues, particularly in maintaining a consistent gap under varying operating conditions.
Innovation Solution
A hydrostatic seal assembly with a seal carrier featuring a radial outer wall, axial wall, and carrier arm that extends at an angle of between −45 degrees and 45 degrees, secured to a static structure via a carrier flange, providing increased compliance and flexibility to accommodate thermal growth differences between components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hydrostatic seal is used to maintain a consistent gap between rotating and static components, then leakage is reduced and sealing efficiency is improved, but thermal stresses increase during transient operating conditions due to thermal expansion differences
Solution Approach 1:
The seal carrier is designed with dynamic compliance to adapt to thermal expansion differences between rotating and static components. The carrier can deform elastically under thermal stress while maintaining seal functionality, allowing the seal to remain effective during transient operating conditions without rigid constraint that would cause excessive stress
Solution Approach 2:
The seal carrier's physical parameters (shape, dimensions) are specifically designed to accommodate thermal growth. The carrier includes features such as curved surfaces, varying thickness sections, and strategic reinforcement zones that allow controlled deformation under thermal stress while maintaining the sealing gap, effectively managing the stress-parameter relationship
2Stress or pressure
If the carrier arm is extended to provide compliance and accommodate thermal growth, then thermal stress is reduced, but the structural complexity of the seal carrier increases
Solution Approach 1:
The seal carrier is divided into distinct functional segments: a radial outer wall for structural support, an axial wall for positioning, and a carrier arm for compliance. This segmentation allows each part to be optimized independently for its specific function while simplifying the overall design through modular functionality
Solution Approach 2:
The carrier arm extends in a specific angular range (−45 to 45 degrees) from the radial outer wall, utilizing angular orientation to achieve compliance in a controlled direction. This dimensional approach allows the structure to accommodate thermal growth through geometric configuration rather than complex multi-directional mechanisms
3Ease of manufacture
If the seal carrier is designed with a unitary structure for simplicity of manufacture, then manufacturing ease is improved, but adaptability to accommodate thermal expansion differences is reduced
Solution Approach 1:
The unitary seal carrier incorporates local variations in geometry and material properties to achieve compliance. Specific regions such as the carrier arm and connection zones have optimized thickness, curvature, and cross-sectional properties that provide thermal adaptability, while the overall structure remains a single piece for manufacturing simplicity
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 reduces thermal stresses and maintains a consistent air gap, enhancing the sealing efficiency and reducing leakage in gas turbine engines by allowing for radial movement of the seal shoe and accommodating thermal expansion differences between rotating and static components.
Implementation Method 1
a shoe having radial travel in response to a pressure differential across the seal
Implementation Method 2
Depending on thermal properties and hardware configuration of the gas turbine engine, the hydrostatic seal may be subject to high stresses during transient operating conditions as components thermally expand into one another
Data Source
AI summary
A hydrostatic seal assembly includes a primary seal assembly configured to maintain a selected gap between the primary seal and a rotating component, and a seal carrier. The seal carrier includes a radial outer wall, an axial wall extending from the radial outer wall at a first axial end of the radial outer wall, and a carrier arm extending from the radial outer wall at a second axial end of the radial outer wall opposite the first axial end. The carrier arm is secured to a static structure for sealing between the rotating component and the static structure.