Gas Turbine Seal Assembly with Tortuous Path and Restrictor
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Solution Overview
Problem
Conventional seal designs for bearing chambers in gas turbine engines fail to prevent oil leakage when the engine is in a vertically oriented position, as the pressure differential reduces and oil seeps into the seal controlled gap by capillarity, leading to contamination of the air side.
Innovation Solution
A seal assembly with an annular lip and a second annular runner forming a tortuous path, combined with a restrictor to impede oil passage, ensuring effective sealing in both horizontal and vertical engine positions by creating a channel that prevents oil from escaping, even when the engine is shut down.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional seal design with a dripping groove is used, then oil leakage can be addressed in horizontal position, but the seal becomes useless in vertical position where shaft slope points upward
Solution Approach 1:
The seal assembly is divided into multiple functional segments: a controlled gap seal element for primary sealing, an annular lip extending axially to create a barrier, a second annular runner forming a tortuous path, and a restrictor to impede oil passage. Each segment contributes to sealing effectiveness in different orientations, making the overall system adaptable to both horizontal and vertical positions.
Solution Approach 2:
The seal design transitions from a simple radial seal to a multi-dimensional structure with axial extension (annular lip), radial spacing (second annular runner), and restricted flow paths. The tortuous path created by the second annular runner and restrictor adds dimensional complexity that prevents oil migration in vertical orientation while maintaining sealing in horizontal position.
2Reliability
If pressure differential is maintained positive relative to bearing chamber, then air flows into bearing cavity under all operating conditions, but when engine shuts down pressure reduces and oil seeps into seal controlled gap by capillarity
Solution Approach 1:
The annular lip and second annular runner with restrictor create a preliminary barrier that prevents oil from reaching the controlled gap seal element before capillary action can cause leakage. This anti-action is built into the structure itself, providing protection even when pressure differential reduces during shutdown.
Solution Approach 2:
The tortuous path formed by the second annular runner and restrictor acts as an intermediary barrier between the bearing cavity and the controlled gap seal. This intermediate structure impedes oil passage through capillary action while allowing the seal element to maintain its primary sealing function under pressurized operation.
3Ease of manufacture
If a dripping groove is provided on the runner outside diameter, then oil leakage can be managed in horizontal position, but this feature becomes useless in vertical position
Solution Approach 1:
The seal assembly is designed to perform multiple functions: the controlled gap seal element provides primary sealing, the annular lip creates an axial barrier, the second annular runner forms a tortuous path, and the restrictor impedes oil flow. This multi-functional design enables the seal to operate effectively in both horizontal and vertical positions, as well as intermediate orientations, making it universal for tilt-rotor engine applications.
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 seal assembly effectively contains lubrication oil within the bearing chamber, maintaining a sealed environment regardless of the engine's orientation, thereby preventing oil leakage and ensuring reliable lubrication and operation in tilt-rotor gas turbine engines.
Implementation Method 1
a restrictor extending between the lip and the second annular runner to impede the passage oil through the tortuous path
Implementation Method 2
oil on the surface may seep by capillarity into the seal controlled gap to the air side of the seal element
Data Source
AI summary
A seal assembly for a bearing assembly in a gas turbine engine includes a first annular runner disposed around a shaft rotatable about an axis defining an axial direction. The first annular runner is rotatable with the shaft about the axis. A seal element is spaced apart from the first annular runner and cooperating therewith to provide a gap seal. An annular lip axially extends from the gap seal to an open end. The lip is disposed at least partially around the seal runner. A second annular runner is disposed coaxially with and spaced radially apart from the lip. The second annular runner extends axially opposite to the lip so as to provide a tortuous path leading to the open end of the lip. A restrictor extends between the lip and the second annular runner to impede the passage oil through the tortuous path to the open end of the lip.