Hula Seal Segmentation for Thermal Expansion Stress
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Solution Overview
Problem
Hula seals in gas turbines are prone to stress cracks and fatigue due to material differences and temperature variations, leading to joint failure and reduced sealing efficiency.
Innovation Solution
A hula seal design featuring two leaves formed from a single integral piece with slits and connection pieces, allowing for relative movement and attachment, reducing stress and fatigue, and providing improved thermal expansion tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the hula seal is made of different material than the attached part, then the seal can provide good sealing performance, but stress cracks and fatigue occur due to thermal expansion differences
Solution Approach 1:
The hula seal is divided into multiple leaves that are separated by slits, allowing each leaf to move independently. This segmentation enables the seal to accommodate thermal expansion differences between the seal material and the attached part, reducing stress concentration and preventing fatigue cracks while maintaining sealing effectiveness.
Solution Approach 2:
The leaves are designed to be movable relative to each other through the slits, transforming the rigid structure into a dynamic one. This allows the seal to adapt to thermal expansion and contraction during operation, reducing stress on the welded joints and preventing failure due to thermal cycling.
2Stability of the object's composition
If the leaves are rigidly attached to maintain structural integrity, then the seal provides stable structure, but twisting occurs that decreases sealing efficiency
Solution Approach 1:
By dividing the seal into multiple leaves with slits between them, the structure gains flexibility while maintaining overall integrity. Each leaf can adjust its position independently to prevent twisting, ensuring the seal maintains contact with the mating surface for effective sealing.
Solution Approach 2:
The design allows changes in the positional parameters of individual leaves relative to each other, enabling the seal to accommodate thermal deformation without twisting. This maintains both structural stability and sealing efficiency under varying temperature conditions.
3Ease of manufacture
If the leaves are made from separate pieces and attached, then assembly is easier, but more attachment points create more potential failure points
Solution Approach 1:
The leaves are formed as a single integral piece with slits between them, eliminating the need for multiple attachment points between leaves. This merging approach reduces the number of potential failure points while maintaining the flexibility benefits of multiple leaves. The entire seal can still be attached to the part at fewer locations.
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 design reduces high and low cycle fatigue cracks, enhances sealing efficiency by minimizing twisting, and improves the stiffness of the seal, making it more effective in maintaining a tight seal across varying temperatures.
Implementation Method 1
the gas turbine component and the hula seal are made of materials with different thermal expansion coefficients and/or where the hula seal and the gas turbine part are at different temperatures or heat up or cool down at different rates during use
Data Source
Figure 1
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AI summary
A hula seal (10) is provided, the hula seal extending in a circumferential direction (5), a radial direction (6) and an axial direction (4) relative to a central axis (3). The hula seal extends in the axial direction from a first edge region (13) at a first edge (12) to a second edge region (15) at a second edge (14). The hula seal comprises a first leaf (20) extending from the first edge region to the second edge region and a second leaf (21) extending from the first edge region to the second edge region. The first leaf is the same distance as the second leaf from the central axis in the radial direction when installed in a gas turbine. The first leaf is adjacent to and overlaps the second leaf in the circumferential direction when installed in a gas turbine. The first leaf is attached to the second leaf such that the first leaf can move relative to the second leaf in the circumferential direction when installed in a gas turbine. A method of installing a hula seal in a gas turbine is also described.