Flexure Rod Bellows Joint for Thermal and Dynamic Duct Loading

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Solution Overview

Problem

Current duct assemblies in gas turbine engines face challenges in providing both rigidity under dynamic loading and flexibility under thermal loading, leading to compromised system dynamic performance and increased weight due to the use of ball-joints or axial-joints.

Innovation Solution

A flexible joint assembly using a bellows with a mounting assembly and rod assemblies that act as spherical flexures, allowing three rotational degrees of freedom, coupled with a protective sheath to manage bending moment loading, providing a frictionless and wear-free connection between ducts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If ball-joints or axial-joints are used in the duct assembly, then flexibility under thermal loading is improved, but system dynamic performance is compromised and weight increases

Engineering Contradiction:

Improveflexibility under thermal loadingVSAvoidsystem dynamic performance

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The joint assembly is divided into distinct functional components: a bellows element for thermal flexibility, rod assemblies for dynamic rigidity, and mounting assemblies for structural support. This segmentation allows each component to specialize in its function, resolving the contradiction between flexibility and dynamic performance

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The rod assemblies act as spherical flexures that provide dynamic rigidity while allowing controlled movement. The system transitions from static rigid connections to dynamic adaptive connections that maintain performance under varying thermal and mechanical conditions

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If ball-joints or axial-joints are used in the duct assembly, then flexibility under thermal loading is improved, but system weight increases

Engineering Contradiction:

Improveflexibility under thermal loadingVSAvoidsystem weight

Core Design Contradiction:

Adaptability or versatilityVSWeight of moving object

Solution Approach 1:

The bellows element uses a flexible corrugated structure to provide thermal expansion accommodation without requiring heavy rigid joints. This flexible shell approach reduces weight compared to traditional ball-joints while maintaining the required flexibility

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

By dividing the joint into lightweight functional segments (bellows for flexibility, rods for rigidity, mounts for support), the overall weight is reduced compared to monolithic heavy-duty joints that would be required to handle all loads simultaneously

Inventive Principle:

Principle #1Segmentation

3Strength

If traditional rigid duct connections are used, then rigidity under dynamic loading is improved, but flexibility under thermal loading is compromised

Engineering Contradiction:

Improverigidity under dynamic loadingVSAvoidflexibility under thermal loading

Core Design Contradiction:

StrengthVSAdaptability or versatility

Solution Approach 1:

The rod assemblies function as spherical flexures that adapt their stiffness characteristics based on loading conditions. They provide rigidity when dynamic loads are applied while allowing thermal expansion movements, creating a dynamic response to different operational conditions

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The separation of thermal flexibility functions (bellows) from dynamic rigidity functions (rod assemblies) allows each component to be optimized for its specific purpose, resolving the contradiction between thermal adaptability and dynamic strength

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 solution reduces reaction loading and enhances rotational compliance, resulting in a lightweight, compact, and simplified design that mitigates thrust and shear loads without interfacial wear or friction, improving the performance of high-temperature bleed-air ducting systems.

Implementation Method 1

The set of rod assemblies is configured to act as spherical flexures to allow three rotational degrees of freedom at the flexible joint assembly

Methodology Applied

Scientific EffectSpherical flexure:

Implementation Method 2

the protective sheath includes one of a helical coil or a set of apertures to tailor a bending moment loading for the set of rod assemblies

Methodology Applied

Scientific EffectBending moment loading:

Data Source

PatentEP3354578B1Flexible joints assembly with flexure rods

Publication Date: 2021.04.28 UNISON INDUSTRIES LLC

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AI summary

A flexible joint assembly (86) for a joint between a first duct (82) and a second duct (84) for providing a flow of fluid, such as bleed air in an aviation implementation. The flexible joint (86) includes a bellows (102) supported by a mounting assembly (96) having a first support (98) and a second support (100), each surrounding a portion of the bellows (102). A set of rod assemblies (110) can operably couple the first support (98) and the second support (100).