Gas Turbine Fan Axial Retention via Drum Catcher

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Solution Overview

Problem

Existing gas turboshaft engines face challenges in retaining the fan assembly during breakage of the driving shaft, particularly when the breakage occurs upstream of the bearing, leading to unbalanced oscillations and increased dynamic loads, which can cause collateral damage and require heavier engine structures to manage stresses.

Innovation Solution

The implementation of axial retention means integrated with the driving drum, which comes into contact with the fan assembly to prevent axial movement in case of shaft breakage, utilizing the drum's shape and abradable coatings to absorb shocks and maintain structural integrity without adding complex retention devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of stationary object

If a decoupling device is used to reduce dynamic loads in the fan, then the engine structure can be lighter, but the risk of breakage of the low-pressure driving shaft increases

Engineering Contradiction:

Improveengine structure weightVSAvoidshaft breakage risk

Core Design Contradiction:

Weight of stationary objectVSReliability

Solution Approach 1:

The patent implements a catcher device with an annular rim that axially retains the low-pressure shaft upstream of the bearing in advance, preparing a safety mechanism before shaft breakage occurs. This allows the decoupling device to be used for weight reduction while the catcher provides preliminary protection against shaft failure consequences

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Stress or pressure

If the fan is decoupled to reduce dynamic loads at high RPM, then structural stresses are reduced, but the only mode of operation becomes low RPM

Engineering Contradiction:

Improvestructural stressVSAvoidoperational mode range

Core Design Contradiction:

Stress or pressureVSAdaptability or versatility

Solution Approach 1:

The patent employs a dynamic retention system where the catcher device remains inactive during normal operation but automatically activates upon shaft breakage. The annular rim can engage with the shaft in both axial directions, providing adaptive retention that responds to operational conditions without restricting normal high-RPM or low-RPM operation

Inventive Principle:

Principle #15Dynamics

3Reliability

If a catcher with an annular rim is used to retain the shaft upstream of the bearing, then axial retention is achieved, but the solution is ineffective for breakage upstream of the bearing

Engineering Contradiction:

Improveshaft retention capabilityVSAvoidbreakage location coverage

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent designs the catcher device with an annular rim that can retain the shaft regardless of breakage location. The rim is configured to engage with the shaft upstream of the bearing and can effectively retain the shaft even when breakage occurs at different positions, making the single device universally effective for various breakage scenarios

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9341116B2Gas turbine engine comprising means for axially retaining a fan of the engine

Publication Date: 2016.05.17 SAFRAN AIRCRAFT ENGINES SAS

AI summary

A gas turbine engine including: a casing in which is mounted at least one shaft for driving a fan solidly connected to a driving drum including blades to compress an airflow moving from upstream to downstream in the engine; and an axial retention mechanism, on standby, solidly connected to the casing and arranged to come into contact with the driving drum such as to prevent axial movement of the drum in event of breakage of the driving shaft.