Leaf Spring Spacer for Gas Turbine Blade Root

Solution Overview

Problem

Existing gas turbine engine blade mounting arrangements are complex, heavy, and costly due to the use of metallic and elastomeric spacers to prevent movement between fan blade roots and hub slots during windmilling, leading to inefficiencies and increased assembly and maintenance difficulties.

Innovation Solution

A lightweight leaf spring spacer is used between the radially innermost end of the fan blade root and the hub slot, held by an interference fit to exert a radially outward force, preventing unwanted radial movement and tilting of the blade root, with a dovetail shape and angularly offset side surfaces to secure the blade within the slot.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If complex metallic and elastomeric spacers are used to prevent blade root movement during windmilling, then reliability is improved, but device complexity and weight increase

Engineering Contradiction:

Improveprevention of blade root movement and wearVSAvoidcomplexity of spacer configuration

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the essential function of the spacer (preventing radial movement) from the complex metallic and elastomeric configurations by using a simple leaf spring mechanism. The leaf spring spacer removes unnecessary complexity while maintaining the core protective function against windmilling-induced movement and wear.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the material and structural parameters of the spacer from complex metallic/eastomeric compositions to a simple leaf spring design. This parameter change reduces device complexity and weight while maintaining the reliability function through the inherent elastic properties of the leaf spring.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If complex metallic and elastomeric spacers are used to prevent blade root movement during windmilling, then reliability is improved, but weight increases

Engineering Contradiction:

Improveprevention of blade root movement and wearVSAvoidweight of spacer and blade assembly

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The patent extracts the essential function of the spacer (preventing radial movement) from the complex metallic and elastomeric configurations by using a simple leaf spring mechanism. The leaf spring spacer removes unnecessary complexity while maintaining the core protective function against windmilling-induced movement and wear.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the material and structural parameters of the spacer from complex metallic/eastomeric compositions to a simple leaf spring design. This parameter change reduces device complexity and weight while maintaining the reliability function through the inherent elastic properties of the leaf spring.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If complex metallic and elastomeric spacers are used to prevent blade root movement during windmilling, then reliability is improved, but ease of manufacture and assembly deteriorates

Engineering Contradiction:

Improveprevention of blade root movement and wearVSAvoidease of assembly and maintenance

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent extracts the essential function of the spacer (preventing radial movement) from the complex metallic and elastomeric configurations by using a simple leaf spring mechanism. The leaf spring spacer removes unnecessary complexity while maintaining the core protective function against windmilling-induced movement and wear.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the material and structural parameters of the spacer from complex metallic/eastomeric compositions to a simple leaf spring design. This parameter change reduces device complexity and weight while maintaining the reliability function through the inherent elastic properties of the leaf spring.

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 solution minimizes movement and wear between fan blade roots and hub slots during windmilling, reducing the complexity and weight of the engine while maintaining efficient assembly and maintenance, and is applicable to various gas turbine engine blades.

Implementation Method 1

The spacer is held in place by an interference fit between the blade root and the slot such that the spacer exerts a radially outward force on the blade root to secure the blade root within the slot

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

The spacer is held in place by an interference fit between the blade root and the slot such that the spacer exerts a radially outward force on the blade root

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentEP2395200B1Gas turbine engine blade mounting arrangement

Publication Date: 2020.07.29 RTX CORP

Figure 1
Figure 2
Figure 3~4

AI summary

A mounting arrangement for a gas turbine engine blade (70) having a root (80) employs a lightweight, simple and economical leaf spring spacer (125) which biases the blade root (80) in a radially outward direction to minimize unwanted movement of the root (80) within a conforming slot (85) in a blade hub (60) under conditions such as windmilling when centrifugal force alone is inadequate to tightly seal the root (80) within the slot (85).