Segmented Carbon Seal Pressure Balancing for Oil Leakage Control
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Solution Overview
Problem
Existing seal systems in gas turbine engines face challenges in effectively isolating oil-containing bearing compartments, particularly in maintaining a sufficient pressure difference to prevent oil leakage, while minimizing wear and ensuring structural integrity.
Innovation Solution
A segmented seal system with arcuate body segments featuring circumferential channels and dams, where the ID face channel has an open end and is deeper and wider than the OD face channel, allowing for efficient airflow and pressure distribution, and a garter spring biasing the segments to maintain contact and structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the ID face circumferential channel is made deeper and wider with an open end, then airflow efficiency and pressure distribution are improved, but the complexity of the seal structure increases
Solution Approach 1:
The seal is divided into multiple segments that can be assembled together, with each segment containing the complex channel structure. This segmentation allows the complicated ID face circumferential channel with open end to be manufactured and assembled more easily, reducing overall structural complexity while maintaining airflow efficiency
Solution Approach 2:
The ID face circumferential channel is designed with non-uniform characteristics (deeper and wider in specific regions, with an open end) to optimize airflow distribution locally where it is most needed, rather than uniformly throughout the entire seal structure
2Stress or pressure
If circumferential grooves are added to distribute high pressure gas, then pressure balancing is improved, but the span of dams increases which reduces buffering effectiveness
Solution Approach 1:
The circumferential grooves are positioned and sized to provide sufficient pressure distribution with minimal dam span. By using partial action (grooves at specific locations rather than continuous grooves), the design achieves adequate pressure balancing while minimizing the reduction in buffering effectiveness
3Reliability
If the seal operates with pressure difference to limit oil leakage, then sealing performance is improved, but wear increases due to contact between seal segments
Solution Approach 1:
The seal design uses the pressure difference across the seal to self-regulate the contact conditions between segments. The high pressure side pushes the segments into light contact with the runner, while the low pressure side allows for clearance, creating a self-adjusting mechanism that maintains sealing performance while minimizing wear over the service life
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 enhances pressure balancing, tolerance to wear, and structural integrity, reducing oil leakage and maintaining effective sealing performance over the lifespan of the seal.
Implementation Method 1
The segments are biased circumferentially inward via a garter spring (e.g., tension coil spring) encircling the array and captured in an outer diameter (OD) groove of each segment
Implementation Method 2
For distribution of high pressure gas (e.g., the buffer air), the seals typically have open passageways along the respective low pressure face and ID face
Implementation Method 3
a contacting carbon seal allows the required pressure drop
Data Source
AI summary
A seal segment has an arcuate body having: a first end; a second end circumferentially opposite the first end; a first face; a second face axially opposite the first face; an inner diameter (ID) face; and an outer diameter (OD) face. The seal segment is shaped to interfit with a plurality of identical seal segments first end to second end to form a seal surrounding a central longitudinal axis. The first face has: a circumferential channel closer to the ID face than the OD face; and a plurality of channels extending from the circumferential channel to the OD face. The ID face has: a circumferential channel closer to the first face than the second face; and a plurality of channels extending from the circumferential channel to the second face. The ID face circumferential channel has an open end.