Undulating Balance Bracket for Diffuser Case Stress Relief

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Solution Overview

Problem

Gas turbine engines face challenges in stress relief for diffuser cases due to thermal and mechanical stresses, leading to cyclic fatigue and potential failure of mounting brackets under repeated expansion and contraction.

Innovation Solution

A balance bracket with undulating portions is designed for mounting to bosses on the diffuser case, allowing for radial expansion and providing localized support to mitigate stress concentrations, featuring reduced thickness and width sections that can bend or crease to accommodate thermal expansion without hindering the diffuser case's expansion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a rigid balance bracket is used to provide strong mounting support, then structural strength is improved, but stress concentrations and cyclic fatigue occur under thermal expansion and contraction

Engineering Contradiction:

Improvestructural strengthVSAvoidresistance to cyclic fatigue

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The balance bracket transitions from a rigid structure to a dynamic one with undulating portions that can flex and deform elastically. These undulating portions allow the bracket to adapt its stiffness dynamically - remaining rigid when needed for structural support but flexible enough to accommodate thermal expansion and contraction cycles without accumulating damaging stresses.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The cross-sectional geometry of the balance bracket is varied along its length, with undulating portions having reduced thickness compared to the nominal thickness of the bracket. This parameter change creates a gradient in stiffness - the thinner undulating sections are more compliant and can deform to relieve stress, while thicker sections maintain structural integrity.

Inventive Principle:

Principle #35Parameter changes

2Strength

If the balance bracket is made with uniform thickness to maintain structural integrity, then strength is improved, but thermal expansion is hindered causing stress concentrations

Engineering Contradiction:

Improvestructural integrityVSAvoidthermal expansion accommodation

Core Design Contradiction:

StrengthVSAdaptability or versatility

Solution Approach 1:

The balance bracket features non-uniform thickness distribution with undulating portions having locally reduced thickness. These localized thin sections serve as expansion joints that specifically accommodate thermal growth of the diffuser case, while the remaining thicker portions of the bracket maintain overall structural integrity and mounting strength.

Inventive Principle:

Principle #3Local quality

3Adaptability or versatility

If the balance bracket thickness is reduced to allow thermal expansion, then adaptability is improved, but structural strength decreases

Engineering Contradiction:

Improvethermal expansion accommodationVSAvoidstructural strength

Core Design Contradiction:

Adaptability or versatilityVSStrength

Solution Approach 1:

The balance bracket is segmented into regions of different thickness - undulating portions with reduced thickness for flexibility and nominal thickness portions for strength. This segmentation allows each region to perform its specialized function: the thin undulating sections accommodate thermal expansion while the thicker sections provide structural support and mounting capability.

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

The undulating balance bracket effectively relieves stress and supports the diffuser case during thermal expansion, preventing fatigue and failure by allowing for circumferential expansion while maintaining structural integrity.

Implementation Method 1

allowing for radial expansion and providing localized support to mitigate stress concentrations, featuring reduced thickness and width sections that can bend or crease to accommodate thermal expansion

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentUS11002153B2Balance bracket

Publication Date: 2021.05.11 RTX CORP

AI summary

A balance bracket for a diffuser case of gas turbine engine is disclosed. In various embodiments, the balance bracket includes a first portion configured for mounting to a first boss on the diffuser case, a second portion configured for mounting to a second boss on the diffuser case, the second portion spaced a distance from the first portion, and a first undulating portion positioned intermediate the first portion and the second portion.