Intershaft Seal Spring-Loaded Runner Design
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Solution Overview
Problem
Existing intershaft seals in gas turbine engines face issues with wear, leakage, and assembly complexity due to axial rubbing contact and varying clearances caused by thermal expansion and manufacturing tolerances, leading to inconsistent sealing performance over time.
Innovation Solution
A spring-loaded runner design with lift-generating formations on the sealing interfaces, allowing the sealing ring to maintain low axial clearances and prevent wear, while compensating for thermal expansion and manufacturing imperfections, and simplifying the assembly process by reducing the number of components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the distance between runners is reduced to maintain low axial clearances, then sealing performance is improved, but thermal expansion and manufacturing tolerances cause excessive fluid leakage
Solution Approach 1:
The seal ring is made flexible through a laminated construction of multiple disc layers bonded together, allowing it to dynamically adjust its shape and maintain consistent sealing contact despite thermal expansion and manufacturing variations. The flexible seal ring can deform to accommodate clearance changes while maintaining reliable sealing performance.
Solution Approach 2:
The seal ring uses a composite laminated structure consisting of multiple disc layers (e.g., metal and polymer layers) bonded together. This composite construction provides both flexibility for adaptation to clearance variations and structural integrity for reliable sealing, resolving the contradiction between precision and reliability.
2Reliability
If a split ring design with spring element is used to compensate for clearance variations, then sealing reliability is improved, but device complexity and assembly difficulty increase
Solution Approach 1:
The flexible seal ring integrates the compensation function previously requiring separate spring elements and split ring components into a single unified structure. The laminated construction itself provides the necessary flexibility and compensation capability, eliminating the need for additional springs and simplifying the overall design.
Solution Approach 2:
The complex spring element and split ring mechanism is extracted and replaced by the inherent flexibility of the laminated seal ring structure. This extraction simplifies the device by removing unnecessary components while maintaining the essential function of compensating for clearance variations.
3Temperature
If carbon ring is designed with slight clearance from outer shaft at cold build, then thermal expansion is accommodated, but excessive fluid leakage occurs during operation
Solution Approach 1:
The flexible laminated seal ring dynamically adjusts its position and shape in response to thermal expansion. As temperature increases and components expand, the flexible seal ring deforms to maintain optimal sealing contact, preventing excessive fluid leakage while accommodating thermal growth.
Solution Approach 2:
The physical parameters of the seal ring (flexibility, shape, position) are allowed to change in response to temperature variations. The laminated construction enables the seal ring to change its effective clearance and contact pressure to maintain sealing performance across different thermal conditions.
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 wear, maintains low axial clearances, and improves sealing performance by compensating for thermal expansion and manufacturing tolerances, while simplifying assembly and reducing leakage, thus enhancing the reliability and consistency of the seal over its lifespan.
Implementation Method 1
a spring element 45 (e.g. a wave spring) positioned between the two halves and urging the halves towards respectively the first runner and the second runner
Implementation Method 2
the incorporation of lift generating formations, such as V-grooves, in the surfaces of the runners at the sealing interfaces 39, 40. Such formations generate lift as the axial clearance of the sealing reduces, thereby causing the ring 35 to move axially
Implementation Method 3
During operation, the carbon ring is pushed by centrifugal forces into more intimate sealing contact with the outer shaft and rotates with that shaft
Implementation Method 4
rubbing contact at the respective sealing interface 39, 40 can occur, such rubbing contact producing sufficient axial force to overcome the frictional resistance to sliding axial movement of the carbon ring 35 along the outer shaft 38
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
An intershaft seal is provided for inner 57 and outer coaxial shafts 58 which rotate relative to each other. The seal is located in an annular space between the shafts and maintains an axial fluid pressure differential between a first side 51 of the seal and a second side 52 of the seal. The seal includes first and second runners (53, 54) which project into the annular space from a first one of the shafts and extend circumferentially around the first shaft such that a cavity is formed between the runners. The seal further includes a sealing ring 55 which is coaxial with the shafts and is located in the cavity. The sealing ring makes sealing contact with the second of the shafts to maintain the pressure differential. One of the runners is spring-loaded such that it is urged towards the sealing ring.