Turbomachine Blade Leading Edge Reinforcement FOD Protection

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Solution Overview

Problem

Turbomachine blades face significant costs and downtime due to the detachment of leading edge reinforcements during Foreign Object Damage (FOD) impacts, which causes damage to internal abradable layers and requires complete engine immobilization for replacement.

Innovation Solution

A leading edge reinforcement design with a radially outer edge that is spaced and curved, preventing penetration into the internal abradable layer upon separation, and made of metallic materials for enhanced protection, allowing for simpler and less costly maintenance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the leading edge reinforcement is made extensive to cover the entire blade surface, then the protection against FOD is improved, but the risk of penetration into the abradable layer upon separation increases

Engineering Contradiction:

Improveprotection against FODVSAvoidpenetration into abradable layer

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The reinforcement is designed with non-uniform coverage: the intrados fin extends radially further than the extrados fin. This local differentiation ensures adequate protection on the intrados side where penetration risk is highest, while limiting extrados fin extent to prevent abradable layer damage upon separation.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The reinforcement structure is asymmetric with respect to blade surfaces: the intrados fin has greater radial extension than the extrados fin. This asymmetry addresses the different risk profiles of each surface, providing enhanced protection where needed while minimizing harmful penetration elsewhere.

Inventive Principle:

Principle #4Asymmetry

2Reliability

If the fin extends close to the blade tip to maximize protection, then the FOD resistance is improved, but the separation distance from the abradable layer is reduced

Engineering Contradiction:

ImproveFOD resistanceVSAvoiddistance from abradable layer

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The fin design implements local quality by extending the intrados fin closer to the blade tip for maximum protection, while maintaining a controlled distance for the extrados fin to prevent abradable layer penetration upon separation.

Inventive Principle:

Principle #3Local quality

3Reliability

If the reinforcement structure is made complex to improve stress distribution, then the FOD protection is enhanced, but the manufacturing complexity increases

Engineering Contradiction:

Improvestress distributionVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The reinforcement is segmented into two distinct fins (intrados and extrados) with different geometries and attachment configurations. This segmentation allows each fin to be optimized for its specific function while simplifying the overall manufacturing process compared to a monolithic complex structure.

Inventive Principle:

Principle #1Segmentation

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 limits the penetration of detached fins into the internal abradable layer and effectively distributes impact forces, reducing maintenance costs and downtime by allowing for repair of individual blades rather than complete engine shutdown.

Implementation Method 1

the second portion of the radially outer edge of the extrados fin is convexly curved. This particular shape facilitates the manufacture of the reinforcement and also limits the creation of disturbances in the airflow

Methodology Applied

Scientific EffectAirflow disturbance: Turbulence

Implementation Method 2

the air comes into contact with the lower surface thus creating an overpressure on the lower surface and a depression on its upper surface. The overpressure generated on the lower surface tends to limit the separation of the lower wingtip to the lower surface. Conversely, the combination of the centrifugal force, which is greater at the blade tip than at the root, with the low pressure generated on the upper surface, tends to promote separation of the upper wingtip

Methodology Applied

Scientific EffectPressure differential: Pressure Gradient

Implementation Method 3

the combination of the centrifugal force, which is greater at the blade tip than at the root, with the low pressure generated on the upper surface, tends to promote separation of the upper wingtip

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Data Source

PatentEP3315721B1Leading-edge reinforcement of a turbine engine blade

Publication Date: 2022.03.02 SAFRAN AIRCRAFT ENGINES SAS

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AI summary

The invention relates to a turbomachine blade, comprising an aerodynamic surface (28) extending in a first direction between a leading edge (8a) and a trailing edge, and in a second direction substantially perpendicular to the first direction between a root and a tip (8d) of the blade, and a leading edge reinforcement (32) comprising a fin (32a) partially covering the aerodynamic surface (28) of the blade, characterized in that the fin (32a) has a radially external edge (34) arranged in the vicinity of the tip (8d) of the blade and extending between the leading edge (8a) and the trailing edge, this radially external edge (34) comprising an upstream point (34a) flush with the tip (8d) of the blade at the level of the leading edge (8a) and a downstream point (34b) set away from the tip (8d) of the blade.