Angled-Fin Labyrinth Seal for Bearing Cavity Lubricant Containment

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Solution Overview

Problem

Gas turbine engines face challenges in preventing lubricant leakage from bearing cavities while maintaining effective sealing, especially during shutdown when compressed air supply is insufficient.

Innovation Solution

The implementation of a labyrinth seal assembly with angled fins and a radial protrusion, where the seal rotor and stator fins extend in an angled upstream direction and an inboard-most fin is angled differently, enhances sealing efficiency by utilizing compressed air and directing lubricant back into the cavity during shutdown.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If straight fin configurations are used in the labyrinth seal, then the structure is simple and easy to manufacture, but the sealing efficiency is insufficient and lubricant leakage occurs during shutdown

Engineering Contradiction:

Improvesealing efficiencyVSAvoidfin configuration complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies asymmetry by configuring fins at different angles relative to the axial direction. Specifically, fins are arranged with different inclination angles to create asymmetric flow paths that enhance sealing efficiency. This asymmetric configuration optimizes the interaction between compressed air and lubricant, preventing leakage during shutdown while maintaining reasonable structural complexity.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent introduces angular dimensionality to the fin configuration. Instead of simple radial fins, the fins extend at various angles from the axial direction, adding an angular dimension to the sealing structure. This dimensional change creates more effective flow control paths for both air and lubricant, significantly improving sealing performance.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Reliability

If tip clearance is reduced to improve sealing, then sealing performance improves, but manufacturing precision requirements increase and operational flexibility decreases

Engineering Contradiction:

Improvesealing performanceVSAvoidtip clearance precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent changes the geometric parameters of the fin structure, specifically the fin angles and their distribution. By optimizing these parameters, the seal achieves effective lubricant containment with larger tip clearances. The parameter optimization allows the sealing performance to improve without requiring tighter manufacturing tolerances on tip clearance.

Inventive Principle:

Principle #35Parameter changes

3Loss of energy

If compressed air supply is reduced during shutdown, then energy consumption decreases, but sealing capability deteriorates and lubricant leakage increases

Engineering Contradiction:

Improvecompressed air consumptionVSAvoidsealing capability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent enables the seal to partially serve itself during shutdown conditions. The asymmetric fin configuration creates flow paths that utilize residual air pressure and lubricant viscosity to maintain sealing. The structure automatically adapts to low air supply conditions by relying on the geometric features to control flow, reducing dependence on high compressed air consumption.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent converts the potential harm of low air pressure during shutdown into a beneficial effect. The asymmetric fin arrangement creates flow patterns where even minimal air pressure effectively controls lubricant flow. The low air supply condition, which would normally be harmful, becomes sufficient for effective sealing due to the optimized fin geometry.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 improves sealing efficiency by approximately 10% compared to straight fin configurations and maintains effective lubricant containment even when air pressure differences decrease, allowing for greater tip clearance without compromising sealing performance.

Implementation Method 1

an air distribution system configured to inject compressed air to the bearing cavity to in use provide a sealing air flow entering the bearing cavity

Methodology Applied

Scientific EffectCompressed air flow: Pressure Gradient

Implementation Method 2

at least one of the fins extending in an angled upstream direction relative to a direction of the sealing air flow

Methodology Applied

Scientific EffectFluid flow direction control: Pressure Gradient

Data Source

PatentUS11293295B2Labyrinth seal with angled fins

Publication Date: 2022.04.05 PRATT & WHITNEY CANADA CORP

AI summary

An aircraft engine having a shaft, an engine casing, at least one bearing located between the shaft and the engine casing, the engine casing defining a bearing cavity containing the at least one bearing, an air distribution system configured to inject compressed air to the bearing cavity to in use provide a sealing air flow entering the bearing cavity, and a labyrinth seal having a seal rotor and a seal stator, fins extending from one of the seal rotor and the seal stator toward the other of the seal rotor and the seal stator, at least one of the fins extending in an angled upstream direction relative to a direction of the sealing air flow.