Spring-Loaded Borescope Plug Sealing for Turbine Inspection Holes
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Solution Overview
Problem
There is a need for improved sealing systems for gas turbine engine inspection holes to prevent fluid leakage between adjacent engine cases during operation.
Innovation Solution
A borescope plug assembly featuring a housing guide, seal ring, restrictor pin, and a plug with a circular restrictor and spring mechanism that maintains a seal despite thermal expansion and contraction of engine components, ensuring proper alignment and minimizing leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a simple seal is used for inspection holes, then device complexity is reduced, but sealing reliability deteriorates due to thermal expansion and contraction
Solution Approach 1:
The sealing system incorporates a spring mechanism that dynamically adjusts the seal ring's position and contact pressure in response to thermal expansion and contraction of the engine case. The spring allows the seal to maintain continuous contact with the mating surface despite dimensional changes, ensuring reliable sealing without requiring an overly complex rigid system.
Solution Approach 2:
The seal ring is made of a material with different thermal expansion characteristics than the engine case, allowing it to compensate for thermal dimensional changes. The spring mechanism also changes its mechanical properties (contact pressure) in response to temperature variations, maintaining effective sealing across the operating temperature range.
2Reliability
If a rigid seal is used to prevent leakage, then sealing effectiveness is improved, but the seal cannot accommodate thermal expansion and contraction
Solution Approach 1:
The spring mechanism transforms the rigid seal into a dynamic system that can adapt to thermal dimensional changes. The spring compresses or extends as the engine case expands or contracts, maintaining constant contact pressure between the seal ring and the mating surface, thus preserving sealing effectiveness while accommodating thermal variability.
Solution Approach 2:
The seal ring functions as a flexible element that can deform elastically under thermal stress while maintaining its sealing function. This flexible component works in conjunction with the spring to accommodate dimensional changes in the rigid engine case without compromising the seal.
3Reliability
If multiple sealing components are added to handle thermal cycles, then sealing reliability is improved, but device complexity increases
Solution Approach 1:
The invention combines the seal ring, spring mechanism, and alignment features into an integrated assembly that functions as a unified sealing system. This merged design achieves reliable thermal compensation and alignment without requiring multiple separate components, thus improving reliability while controlling overall system complexity.
Solution Approach 2:
The sealing assembly performs multiple functions simultaneously: the seal ring provides the primary sealing function, the spring provides both force application and thermal compensation, and the alignment features ensure proper positioning. This multi-functional design reduces the need for additional dedicated components for each function.
4Reliability
If alignment features are added to maintain component alignment during thermal cycles, then operational reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The alignment features utilize asymmetric geometries (such as tapered surfaces or non-circular cross-sections) that provide self-alignment through interference fits or mechanical constraints. These asymmetric features guide the sealing assembly into proper alignment automatically during installation and operation, maintaining alignment stability without requiring complex adjustment mechanisms or precision machining throughout the entire assembly.
Solution Approach 2:
The alignment features are designed to establish proper component positioning during assembly before thermal cycles begin. The geometry of the alignment features pre-positions the sealing assembly correctly, and this preliminary alignment is maintained throughout operation as the spring compensates for thermal dimensional changes, eliminating the need for complex real-time alignment mechanisms.
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 assembly effectively seals inspection holes, reducing fluid leakage and maintaining alignment of engine components during thermal cycles, enhancing operational efficiency and reliability.
Implementation Method 1
maintains a seal despite thermal expansion and contraction of engine components
Implementation Method 2
spring mechanism that maintains a seal
Implementation Method 3
seal ring positioned between the housing and the housing guide
Implementation Method 4
maintaining alignment of engine components during thermal cycles
Data Source
Figure 1
Figure 2~3
Figure 4~6
AI summary
A borescope plug assembly (68) includes a housing (120), a plug (122), and a spring (124). The housing (120) extends between a first housing end (128) and a second housing end (130). The housing (120) includes a plug aperture (134), an internal chamber (132), and a bayonet interface (136). The plug aperture (134) is located at the second housing end (130). The internal chamber (132) extends from the plug aperture (134) toward the first housing end (128). The plug (122) includes a shaft (148), a first sealing surface (154), and at least one tab (156). The shaft (148) extends between a first shaft end (150) and a second shaft end (152). The first sealing surface (154) is disposed at the first shaft end (150). The at least one tab (156) projects radially outward from the shaft (148). The plug (122) extends through the plug aperture (134) with the second shaft end (152) and the at least one tab (156) disposed within the internal chamber (132). The spring (124) is positioned within the internal chamber (132) between the first housing end (128) and the at least one tab (156).