Gas Turbine Seal Assembly With Impeller-Driven Leakage Control
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Solution Overview
Problem
Existing gas turbine engines face challenges in effectively sealing bearing chambers, leading to undesirable leakage due to pressure differentials across mechanical seals, which can result in wear and reduced seal life.
Innovation Solution
A seal assembly is designed for gas turbine engines, featuring a seal bushing, impeller, and extension ring that create a sealing path and displacement flow to manage pressure differentials, preventing leakage by directing air flow and oil within the engine, with the impeller's helical grooves and specific orientation optimizing fluid dynamics to maintain a sealing pressure differential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical seal is used to seal the bearing chamber, then the seal can prevent leakage, but wear occurs and seal life is reduced under certain circumstances
Solution Approach 1:
An aerodynamic film acts as an intermediary between the seal stator and seal runner, preventing direct contact and wear while maintaining sealing effectiveness. The air flow developed between the components creates a protective barrier that eliminates mechanical wear.
Solution Approach 2:
The seal operates using pneumatic principles by developing an aerodynamic film through controlled air flow between the seal components. This pneumatic cushion replaces mechanical contact with fluid pressure, preventing wear and extending seal life.
2Duration of action of moving object
If pressure differential is controlled to preserve seal life, then wear is reduced, but leakage may increase
Solution Approach 1:
The mechanical sealing system is replaced with an aerodynamic sealing system. Instead of relying on mechanical contact and pressure differential control, the seal uses controlled air flow to create a protective film that prevents leakage while eliminating wear.
Solution Approach 2:
The sealing mechanism transitions from mechanical parameter control (pressure differential) to aerodynamic parameter control (air flow rate and velocity). By changing the controlling parameter from pressure to fluid dynamics, both wear reduction and leakage prevention are achieved.
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 minimizes leakage rates and extends the useful life of seal components by maintaining a controlled pressure differential across the seal assembly, enhancing the durability and uptime of the engine.
Implementation Method 1
an impeller rotating with the shaft and located radially inward of the gap relative to the rotation axis, the impeller oriented to drive oil toward the bearing
Implementation Method 2
These seals may be designed to run on an aerodynamic film developed between a stationary outer component (i.e., a seal stator or housing) and a rotating inner component (seal runner or shaft)
Implementation Method 3
Controlling a pressure differential across this interface may preserve seal life
Data Source
Figure 1
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AI summary
A gas turbine engine (10) having a bearing housing (42) with a housing cavity and a shaft (22) rotating about a rotation axis. One or more bearings support the shaft (22). A housing (42) supporting the bearing and defining a chamber axially adjacent to the bearing. A seal assembly (90) is in the housing (44) between the chamber and an exterior of the chamber. The seal assembly (90) includes a seal supported by the housing (44) and surrounding the shaft (22) so as to define an annular gap between an inner surface (60d) of the seal and an outer surface (50d) associated to the shaft (22), the gap defining a part of a sealing path (100) of the seal assembly (90) for air to flow from said exterior into the chamber. An impeller (70) rotates with the shaft (22) and located radially inward of the gap relative to the rotation axis, the impeller (70) oriented to drive oil toward the bearing.