Active Contacting Seal Control for Lubricant Flow Interruptions
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Solution Overview
Problem
Gas turbine engine bearing compartment seals face challenges in maintaining effective contact force under varying lubricant flow conditions, particularly during aircraft maneuvers where oil supply can be interrupted, leading to potential damage if the seal element is subjected to excessive friction and heat.
Innovation Solution
An actively-controlled actuation system is employed, utilizing a rotationally-stationary ramp and a rotationally-movable ramp follower with a wave spring, and a hydraulic actuator to adjust the contact force between the seal element and seat based on lubricant flow, ensuring reduced friction and heat generation by adjusting the contact pressure dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the seal element is urged into contact with the seal seat using coil springs, wave springs, or bellows to maintain sealing, then the seal effectiveness is improved, but the friction and heat generation at the interface increase, especially when lubricant flow is interrupted
Solution Approach 1:
The patent applies dynamics by transitioning from a static spring-based contact force system to a dynamic, actively controlled actuation system. The actuator adjusts the contact force between the seal element and seal seat in real-time based on lubricant flow conditions, allowing the system to adapt its sealing pressure dynamically. This resolves the contradiction by maintaining sufficient contact force for sealing while reducing it when lubricant flow is interrupted, thereby preventing friction and heat damage.
Solution Approach 2:
The patent implements feedback by using sensors to monitor lubricant flow conditions and using this information to control the actuation system. The sensor detects when lubricant flow is interrupted or insufficient, and this feedback signal triggers the actuator to reduce the contact force on the seal element. This closed-loop control system ensures the seal remains effective during normal operation while protecting against damage during lubricant flow interruptions.
2Reliability
If a high contact force is maintained between the seal element and seal seat to ensure sealing under high pressure conditions, then the seal reliability is improved, but the wear and potential damage to the seal element increases during lubricant flow interruptions
Solution Approach 1:
The system dynamically adjusts the contact force based on operating conditions. During normal high-pressure operation, the actuator maintains high contact force to ensure reliable sealing. When lubricant flow is interrupted, the system automatically reduces the contact force, thereby reducing wear and extending the service life of the seal element. This dynamic adaptation resolves the contradiction between maintaining seal reliability and extending component life.
Solution Approach 2:
The actuation system provides beforehand cushioning by detecting lubricant flow conditions in advance and proactively adjusting the contact force before damage can occur. When the sensor detects insufficient lubricant flow, the actuator reduces the contact force preemptively, cushioning the seal element against the harmful effects of dry friction and heat that would otherwise occur during lubricant flow interruptions.
3Object-affected harmful factors
If the contact force is reduced to minimize friction and heat during lubricant flow interruptions, then the seal element protection is improved, but the seal effectiveness deteriorates under normal high pressure operating conditions
Solution Approach 1:
The actuation system dynamically modulates the contact force based on real-time lubricant flow conditions. During normal operation with adequate lubricant flow, the system maintains high contact force for effective sealing. When lubricant flow is interrupted, the system automatically reduces contact force to minimize friction and heat damage. This dynamic control resolves the contradiction by applying the appropriate contact force level for each operating condition.
Solution Approach 2:
The feedback control system continuously monitors lubricant flow conditions and adjusts the contact force accordingly. When the sensor detects sufficient lubricant flow, the actuator maintains high contact force for seal effectiveness. When lubricant flow drops below a threshold, the feedback signal triggers a reduction in contact force to protect the seal element. This feedback mechanism ensures the system responds appropriately to changing conditions, resolving the contradiction between seal effectiveness and friction reduction.
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 system effectively reduces friction and heat generation at the seal interface, minimizing damage during lubricant flow interruptions and extending the service life of the seal elements and seats by dynamically controlling contact force in response to lubricant flow thresholds.
Implementation Method 1
a wave spring, and a hydraulic actuator to adjust the contact force between the seal element and seat
Implementation Method 2
an actuator is operably connected to the ramp follower and is configured to urge circumferential movement of the ramp follower relative to the ramp
Implementation Method 3
a rotationally-stationary ramp including a plurality of ramp teeth, and a rotationally-movable ramp follower including a plurality of complimentary follower teeth meshed with the plurality of ramp teeth
Implementation Method 4
Friction between the seal element and the seal seat is alleviated by a flow of oil between the seal element and seal seat that lubricates the interface
Data Source
AI summary
A contacting seal for a gas turbine engine includes a seal seat configured to rotate circumferentially about an axis of rotation and a seal element configured to contact the seal seat at an interface surface. The seal element is rotationally fixed relative to the axis of rotation. An actively-controlled actuation system is operably connected to the seal element to control a contact force between the seal element and the seal seat at the interface surface based on a level of lubricant flow to the interface surface. A method of operating a contacting seal includes positioning a rotationally fixed seal element in contact with a rotating seal seat at an interface surface between the seal seat and the seal element, and actively-controlling a contact pressure between the seal seat and the seal element at the interface surface utilizing an actuation system.