Deflection Spring Seal Assembly for Intershaft Shaft Deflection
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Solution Overview
Problem
Intershaft seal assemblies in aircraft engines face challenges due to space limitations, unique shaft deflections, and counter-rotating surfaces, leading to thermal mechanical fatigue and difficulty in maintaining necessary gaps, which can result in damage or failure of traditional labyrinth or knife-edge seals during maneuvers.
Innovation Solution
The use of cup washers or spring seals angled relative to the radial direction, allowing them to deflect radially inward during shaft deflection events, preventing wear and critical failure, and minimizing damage by briefly contacting the shaft surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional labyrinth or knife-edge seals are used to maintain transient thermal tolerances, then sealing effectiveness is improved, but the seals are prone to rubbing and thermal mechanical fatigue during shaft deflection events
Solution Approach 1:
The seal assembly incorporates resilient elements that allow the seal to dynamically adapt its position in response to shaft deflection. The resilient elements enable the seal to move radially inward during shaft deflection events, maintaining contact with the shaft surface without rigid constraint, thereby preventing thermal mechanical fatigue while preserving sealing effectiveness.
Solution Approach 2:
The seal assembly changes its radial position parameter dynamically during operation. During normal operation, the seal maintains a specific gap from the shaft. During shaft deflection events, the resilient elements allow the seal to change its radial position by moving inward, adapting to the changed shaft position and avoiding harmful rubbing contact.
2Reliability
If the seal assembly is positioned close to the shaft to maintain necessary gaps during maneuvers, then sealing performance is improved, but the seal is more susceptible to damage during shaft deflection events
Solution Approach 1:
The resilient elements act as a cushioning mechanism positioned between the seal and the shaft. During shaft deflection events, these resilient elements compress first, absorbing the impact energy and preventing direct rigid contact between the seal and shaft, thereby protecting the seal from damage while maintaining close positioning for effective sealing.
3Manufacturing precision
If the seal assembly uses rigid structure to maintain precise positioning, then manufacturing precision is improved, but the seal cannot accommodate unique shaft deflections and counter-rotating surfaces
Solution Approach 1:
The seal assembly transitions from a rigid structure to a dynamic structure incorporating resilient elements. This allows the seal to maintain precise positioning under normal conditions while accommodating shaft deflections and counter-rotating surfaces during operation, resolving the contradiction between manufacturing precision and adaptability.
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
This configuration reduces wear and damage to the seal and shaft, maintaining structural integrity and preventing catastrophic failure during severe events like blade out scenarios, while maintaining effective sealing.
Implementation Method 1
cup washers or spring seals angled relative to the radial direction, allowing them to deflect radially inward during shaft deflection events
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
An intershaft seal assembly that is between a first shaft and a second shaft of a bearing compartment of an engine includes a first seal element and a retaining element. The first seal element surrounds the first shaft and includes a first portion is in contact with the first shaft and a second portion extending in a non-parallel direction to a radial direction of the first shaft. The retaining element is threadably engaged with the first shaft such that the retaining element presses the first seal element against the shoulder of the first shaft.