Double Dam Reverse Pressure Face Seal Assembly
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In jet engines and turbomachinery, pressure reversals cause oil weepage through face seals, leading to leakage and odor issues, as existing seals fail to prevent radially inward oil flow when pressure in the 'air side' drops below the 'oil side' pressure.
Innovation Solution
A double dam reverse pressure face seal assembly is introduced, featuring a first and second annular sealing dam with a channel between them, along with grooves on the mating ring to manage oil flow and air pressure, preventing oil leakage by ensuring the channel pressure remains above the 'oil side' pressure during pressure reversals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single sealing dam is used to prevent oil leakage, then the seal structure is simple, but oil weepage occurs during pressure reversals when air side pressure drops below oil side pressure
Solution Approach 1:
The sealing member is segmented into two distinct sealing dams (first sealing dam and second sealing dam) positioned at different radial locations. The first sealing dam prevents oil leakage during normal operation, while the second sealing dam activates during pressure reversals to prevent oil from entering the air side, thereby resolving the contradiction between reliability during pressure reversal and structural simplicity.
2Reliability
If the sealing member is biased against the mating ring to prevent leakage, then sealing effectiveness is improved, but contact force concentration reduces service life
Solution Approach 1:
The sealing contact force is segmented and distributed across two separate sealing dams instead of being concentrated at a single location. This distribution of contact force across a larger area reduces localized wear and stress concentration, thereby extending the service life of the seal assembly while maintaining effective sealing.
Solution Approach 2:
The sealing interface is extended from a single radial position to multiple radial positions (first and second sealing dams at different radii). This dimensional extension in the radial direction increases the total contact area and distributes the sealing load, improving both sealing effectiveness and durability.
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 prevents oil weepage by maintaining channel pressure above the 'oil side' pressure, reducing leakage and odor issues, and significantly increases the service life of the seal assembly by distributing the contact force and area effectively.
Implementation Method 1
a stationary preferably graphite sealing member that is axially biased, preferably by a wave spring, against an interface surface of the rotating preferably metal mating ring
Implementation Method 2
The second sealing dam has a second contact face connecting to the annular channel by a wall that is diagonal respecting the annular channel bottom and the second contact face, and hence is not parallel to the tunnel axis
Data Source
AI summary
A double dam reverse pressure face seal assembly for use in the turbomachine having a tunnel extending through the machine for high pressure air passage therein during normal machine operating has a mating ring positioned annularly respecting the tunnel for flow of lubricating oil generally outwardly through passageways in the ring and a sealing member biased against an interface surface of the mating ring, the sealing member including a first dam presenting a first contact face to the interface surface of the mating ring, a second dam integral with an outboard of the first dam, presenting a second contact face to the interface surface of the mating ring and a channel between the first and second dams for annularly downward flow of oil leaking inwardly past the second dam towards a channel exit.