Frangible Gas Turbine Airfoil with Chord Reduction

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Solution Overview

Problem

Airfoils in gas turbine engines face challenges with extreme loading events, such as bird strikes, leading to uncontrolled failure modes that increase weight and reduce efficiency, as existing frangible structures are costly and do not adequately address issues of load transfer and rotor unbalance.

Innovation Solution

The airfoil design features a frangible line and chord reductions on the leading and trailing edges, allowing for a controlled failure mode by reducing bending stiffness, enabling the airfoil to break off or deform during failure events, thereby mitigating load transfer to the surrounding casing and reducing unbalance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional frangible structures (honeycombs or trench-filler material) are added to the fan case to mitigate load transfer, then the fan case can withstand impact from fan blade failures, but the weight of the fan case and engine increases, reducing performance and efficiency

Engineering Contradiction:

Improvefan case impact resistanceVSAvoidfan case weight

Core Design Contradiction:

ReliabilityVSWeight of stationary object

Solution Approach 1:

The patent applies this principle by designing the airfoil itself to fail in a controlled manner that converts the harmful impact into a beneficial controlled separation. The frangible line and chord reductions create a predetermined failure path that allows the airfoil to break away safely, protecting the fan case without requiring additional heavy protective structures. The failure mode is transformed from uncontrolled damage to a protective mechanism.

Inventive Principle:

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

Solution Approach 2:

The airfoil is segmented into a frangible portion and a non-frangible portion by introducing a frangible line and chord reductions. This segmentation allows the frangible portion to separate during impact events, reducing load transfer to the fan case. The segmentation eliminates the need for heavy honeycomb or trench-filler structures by making the airfoil itself the protective element through controlled separation.

Inventive Principle:

Principle #1Segmentation

2Reliability

If heavier frangible structures are added to the fan case, then load transfer during fan blade failure is reduced, but the cost of the fan case increases

Engineering Contradiction:

Improveload transfer mitigationVSAvoidfan case cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The airfoil serves dual functions: it performs its aerodynamic role and simultaneously acts as the frangible protective structure. The frangible line and chord reductions are integrated into the airfoil manufacturing process itself, eliminating the need for separate expensive frangible components. The airfoil protects itself and the fan case through its own designed weakness, reducing overall system cost.

Inventive Principle:

Principle #25Self-service

3Reliability

If traditional frangible structures are added to the fan case, then some load transfer is reduced, but the fan case becomes larger and heavier

Engineering Contradiction:

Improveimpact load protectionVSAvoidfan case size

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent extracts the frangible function from the fan case structure and relocates it to the airfoil itself. Instead of adding honeycomb or trench-filler material to the fan case, the frangible line and chord reductions are implemented in the airfoil, which then separates during impact. This extraction eliminates the need for additional fan case volume and weight while maintaining protective function.

Inventive Principle:

Principle #2Taking out (Extraction)

4Reliability

If the airfoil is designed with chord reductions and frangible lines, then controlled failure mode is achieved reducing load transfer, but the airfoil structure becomes more complex

Engineering Contradiction:

Improvecontrolled failure modeVSAvoidairfoil structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The frangible line and chord reductions are preliminary features built into the airfoil during manufacturing. These features pre-establish the failure path before any impact occurs, ensuring controlled separation when needed. The complexity is built in once during manufacturing rather than requiring complex active control systems or additional components during operation.

Inventive Principle:

Principle #10Preliminary action

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 design enables a controlled and consistent failure of the airfoil, reducing weight and cost, while minimizing load transfer and unbalance, thus enhancing the efficiency and performance of gas turbine engines.

Implementation Method 1

The blade defines a first chord reduction on a leading edge of the blade along a first portion of the span. The blade defines a frangible line extending from the first chord reduction at least partially along the chord

Methodology Applied

Scientific EffectBending stiffness reduction:

Data Source

PatentUS10837286B2Frangible gas turbine engine airfoil with chord reduction

Publication Date: 2020.11.17 GENERAL ELECTRIC CO

AI summary

An airfoil defining a span extending between a root and a tip and a chord at each point along the span extending between a leading edge and a trailing edge. The airfoil includes a blade extending between the root and tip and extending between the leading edge and trailing edge. The blade includes a pressure side and a suction side defining a thickness therebetween at each point along the span. The blade defines a first chord reduction on at least one of the leading edge or trailing edge along a first portion of the span. Further, the blade defines a frangible line extending from the first chord reduction at least partially along the chord at a point along the span within the first portion of the span.