Carbon Seal Buffer Air Routing to Limit Turbine Oil Contamination
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Solution Overview
Problem
Gas turbine engines face challenges in preventing oil contamination of the gaspath due to oil infiltration past carbon seals, which can contaminate bleed air used for buffering, leading to inefficiencies and potential damage.
Innovation Solution
A carbon seal system with a buffer air supply path and an oil drain path, utilizing a network of struts and plenums to separate the bearing compartment from the gaspath, where buffer air is introduced through one set of struts and oil is drained through another, with strategically positioned holes and ports to minimize contamination and optimize airflow and drainage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If buffer air is introduced through the shaft to counter oil infiltration, then seal buffering is improved, but oil contamination of the gaspath increases
Solution Approach 1:
The patent divides the buffer air supply system into multiple independent sources: buffer air is supplied through both the shaft and through struts, while oil drainage is handled separately through dedicated drain paths in the struts. This segmentation allows independent control of buffering and drainage functions, preventing oil contamination of the gaspath while maintaining effective seal buffering.
Solution Approach 2:
The struts serve as intermediary structures that facilitate both buffer air supply and oil drainage between the bearing compartment and the gaspath. By routing buffer air and oil drainage through the struts rather than directly through the shaft into the gaspath, the system mediates the interaction between oil-containing bearing compartments and the clean gaspath, preventing contamination.
2Object-affected harmful factors
If separate buffer supply and oil drain paths are implemented, then oil contamination is reduced, but device complexity increases
Solution Approach 1:
The patent combines buffer air supply and oil drainage functions within the same strut structures. The struts contain both buffer air supply paths and oil drain paths, merging multiple functions into a single structural element. This reduces overall system complexity compared to having completely separate systems while still achieving effective oil contamination prevention.
Solution Approach 2:
The struts are designed as multi-functional components that simultaneously serve as structural support elements, buffer air supply conduits, and oil drainage pathways. This universality eliminates the need for dedicated separate structures for each function, reducing device complexity while maintaining effective separation of buffer supply and oil drainage.
3Length of stationary object
If buffer air and oil drainage are consolidated into a single stage of struts, then axial compactness is improved, but manufacturing precision requirements increase
Solution Approach 1:
Within the consolidated strut structure, the patent segments the hole patterns into distinct groups: buffer air supply holes and oil drain holes are positioned at different locations and orientations within the same strut. This internal segmentation allows precise control of each function's airflow characteristics while maintaining overall axial compactness.
Solution Approach 2:
The patent applies local quality by giving different regions of the strut different hole configurations optimized for their specific functions. Buffer air supply regions have hole patterns optimized for outward radial flow, while oil drainage regions have patterns optimized for collecting and removing oil weepage. This localized optimization maintains manufacturing feasibility while achieving precise functional performance.
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 configuration effectively reduces oil contamination of the gaspath, minimizes oil accumulation, and enhances the operational efficiency of the engine by consolidating buffer supply and weepage drain into a single stage of struts, while maintaining axial compactness and reducing the risk of oil reaching the high-pressure compressor first stage disk.
Implementation Method 1
a seal interface between a rotor and a stator that separates a bearing compartment from a gaspath
Implementation Method 2
buffering bleed flow along a buffer flowpath... to counter infiltration of oil along a weepage flowpath
Data Source
AI summary
A turbine engine strut stage extends through a gaspath upstream of a guide vane stage. A carbon seal system seals a bearing compartment and has: a carbon seal mounted to the case and a seal runner on the spool; and a seal carrier carrying the carbon seal. The engine passes buffer air along a buffer air supply path internally through one or more first struts of the stage of struts. The engine drains oil along an oil drain path internally through one or more second struts of the stage of struts.