Labyrinth Seal Abradable Structure for Rotor Lock Prevention

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Labyrinth seals in aircraft turbines face challenges with leakage rates and rotor locking due to differential thermal and mechanical expansions, leading to inefficiencies and safety risks, particularly during engine restarts, as conventional abradable structures are too hard and prone to wiper lock situations.

Innovation Solution

A labyrinth seal abradable structure with progressive wear resistance regions, manufactured using additive techniques, featuring cells with varying sizes and orientations to manage wear and reduce the risk of rotor locking, ensuring optimal permeability and safety by distributing wear resistance accordingly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the abradable structure is made with uniform high wear resistance, then the seal effectiveness is improved, but the risk of rotor locking increases during engine restart

Engineering Contradiction:

Improveseal effectivenessVSAvoidrotor locking risk

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The abradable structure is divided into multiple regions along the axial direction, where each region has different wear resistance properties. The upstream region (facing the wipers) has lower wear resistance to prevent rotor locking, while downstream regions have progressively higher wear resistance to maintain seal effectiveness. This local differentiation resolves the contradiction by providing spatially varying properties tailored to different functional requirements.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The abradable structure is segmented into distinct regions with different wear resistance characteristics. These segments are arranged axially to create a gradient from low wear resistance at the upstream end to high wear resistance downstream. This segmentation allows the structure to simultaneously satisfy conflicting requirements of different zones.

Inventive Principle:

Principle #1Segmentation

2Strength

If the abradable structure has high resistance to impacts, then the structural integrity is improved, but the wiper lock situations are exacerbated

Engineering Contradiction:

Improveimpact resistanceVSAvoidwiper lock situations

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The structure provides locally optimized properties: the upstream region facing the wipers has lower strength and higher abradability to prevent locking, while downstream regions have progressively higher strength to resist impacts. This local quality differentiation resolves the contradiction between impact resistance and wiper lock prevention.

Inventive Principle:

Principle #3Local quality

3Loss of energy

If the clearances between wipers and abradable structure are reduced, then the leakage rate is decreased, but the sensitivity to thermal expansion increases

Engineering Contradiction:

Improveleakage rateVSAvoidthermal expansion tolerance

Core Design Contradiction:

Loss of energyVSAdaptability or versatility

Solution Approach 1:

The wear resistance parameter of the abradable structure is changed along the axial direction, creating a gradient from low wear resistance upstream to high wear resistance downstream. This parameter variation allows the structure to adapt to thermal expansions by providing a compliance zone upstream while maintaining tight clearances downstream for low leakage.

Inventive Principle:

Principle #35Parameter changes

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 abradable structure effectively reduces the risk of rotor locking and maintains efficient leakage flow by adapting wear resistance to different engine phases and thermal expansions, enhancing the safety and performance of aircraft turbines.

Implementation Method 1

the abradable structure, having the property of low resistance to friction and wear

Methodology Applied

Scientific EffectWear: Wear

Implementation Method 2

differential thermal or mechanical expansions (due to overheating or to centrifugal forces)

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 3

differential thermal or mechanical expansions (due to overheating or to centrifugal forces)

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Data Source

PatentUS11428110B2Labyrinth seal abradable structure, notably for aircraft turbine

Publication Date: 2022.08.30 SAFRAN AIRCRAFT ENGINES SAS

AI summary

An abradable structure (36) is provided, with regions (44, 45, 46) with lower resistance to wearing produced by labyrinth seal lips (4, 5), at specific points in the axial direction of the turbomachine, where lip interference could cause the rotor to block up, such as after a temporary shutdown of the turbomachine. These regions may be produced by local weakening (38) or by the abradable material having a structure that is less dense. Application, for example, to turbomachine turbines.