Intershaft Seal Assembly With Hydrodynamic Grooves for Lower Heat
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Solution Overview
Problem
Existing intershaft seal assemblies in gas turbine engines experience high friction and excessive heat generation due to differential rotational speeds between co-axial shafts, leading to increased wear of the seal ring.
Innovation Solution
The proposed intershaft seal assembly features a seal ring positioned between axially spaced annular runners, with a retaining arm connected to a second shaft operating at a lower speed, reducing centrifugal force and incorporating hydrodynamic grooves to minimize friction and contact between the seal ring and runners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the seal ring is brought into contact with the retaining arm to seal the space between shafts, then sealing effectiveness is improved, but friction and heat generation increase due to differential rotational speeds
Solution Approach 1:
A lubricant is introduced as an intermediary substance between the seal ring and retaining arm to reduce direct metal-to-metal contact. The lubricant film separates the two surfaces, allowing them to maintain sealing contact while minimizing friction and heat generation through fluid film lubrication
Solution Approach 2:
The rotational speed parameter of the retaining arm is changed by connecting it to the lower-speed inner shaft rather than the higher-speed outer shaft. This parameter change reduces the differential rotational speed between the seal ring and retaining arm, thereby reducing friction and heat generation while maintaining sealing effectiveness
2Reliability
If the seal ring contacts the retaining arm to maintain sealing under differential pressure, then sealing reliability is improved, but wear of the seal ring increases
Solution Approach 1:
The lubricant acts as a protective intermediary layer between the seal ring and retaining arm, reducing direct abrasive contact. This intermediary film allows the seal ring to maintain contact with the retaining arm for sealing purposes while significantly reducing wear and extending the service life of the seal ring
Solution Approach 2:
The direct mechanical contact system is replaced with a fluid film lubrication system. Instead of relying on solid-to-solid contact for sealing, the patent uses a lubricant film to mediate the interaction, reducing mechanical wear while maintaining the sealing function
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 design significantly reduces heat generation and wear by lowering centrifugal force and radial loading, achieving up to 80% less heat generation compared to prior art, while maintaining effective sealing between high and low pressure fluid cavities.
Implementation Method 1
the centrifugal force from rotation will move seal ring 12 radially outward and into contact with retaining arm 14
Implementation Method 2
incorporating hydrodynamic grooves to minimize friction and contact between the seal ring and runners
Data Source
AI summary
An intershaft seal assembly comprises an annular seal ring disposed between a pair of annular runners connected to a hollow outer rotating shaft, and a surface of a co-axial inner rotating shaft. The centrifugal force resulting from rotation of the hollow outer rotating shaft effects engagement of the annular seal ring with the surface of the co-axial inner rotating shaft. The surface may be a radially-inward-facing surface of a retaining arm connected to the co-axial inner rotating shaft.