High Temperature Flange Joint Bolt Preload Maintenance

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

High temperature flange joints in gas turbine engines face challenges in maintaining bolt preload due to thermal expansion and creep, leading to potential bolt loosening and reduced fatigue life, especially during transient and steady-state operations.

Innovation Solution

The implementation of a high temperature flange joint design featuring spacer plates and lock washers that enhance the bearing surface contact area, reducing thermal gradients and creep deformation, while maintaining bolt preload through a conical pressure distribution and anti-rotation features to prevent bolt loosening.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional bolted flange joint is used in high temperature environment, then the joint can be assembled and disassembled, but the bolt preload is lost due to thermal expansion and creep

Engineering Contradiction:

Improvebolt preload maintenanceVSAvoidhigh steady state temperature

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

A temperature compensating mechanism is introduced as an intermediary element between the flange and bolt. This mechanism includes a bellows-shaped compensation member that can deform elastically in response to temperature changes, thereby absorbing thermal expansion and preventing direct transmission of thermal stresses to the bolt, which maintains bolt preload under high temperature conditions

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the physical state and dimensional parameters of the flange joint system by introducing a bellows-shaped compensation member with specific elastic properties. This member undergoes dimensional changes in response to temperature variations, allowing the system to adapt to thermal conditions while maintaining mechanical integrity and bolt preload

Inventive Principle:

Principle #35Parameter changes

2Reliability

If bolt preload is increased to maintain joint integrity at high temperature, then the joint integrity is improved, but the flange deforms plastically during engine startup

Engineering Contradiction:

Improvejoint integrityVSAvoidflange deformation

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The bellows-shaped compensation member acts as a mediator that decouples the flange from direct thermal loading. By absorbing thermal expansion through elastic deformation, it prevents excessive stress concentration at the flange-bolt interface, thereby preventing plastic deformation of the flange while maintaining joint integrity

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The compensation member is pre-configured with elastic properties that allow it to absorb thermal expansion before it can cause damage to the flange or bolt. This beforehand cushioning effect prevents plastic deformation by providing a compliant element that accommodates thermal stresses

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Device complexity

If conventional flange joint design is used, then the structure is simple, but creep sets in at the flange due to high steady state temperatures

Engineering Contradiction:

Improveflange joint structureVSAvoidservice interval

Core Design Contradiction:

Device complexityVSDuration of action of stationary object

Solution Approach 1:

The bellows-shaped compensation member serves as an intermediary element that reduces creep deformation at the flange by absorbing thermal expansion. This extends the service interval by preventing creep-induced joint failure, while the addition of this single component maintains relative structural simplicity

Inventive Principle:

Principle #24Intermediary (Mediator)

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 effectively maintains bolt preload and reduces flange deformation, extending the service interval and allowing the use of lower-grade materials, thereby improving the overall reliability and fatigue life of the flange joints.

Implementation Method 1

Each of the spacer plates has a respective thickness and is sized to enhance a bearing surface in contact with the respective flange, whereby a bolt preload is maintained during operation of the gas turbine engine

Methodology Applied

Scientific EffectThermal gradient reduction: Temperature Gradient

Implementation Method 2

The plastic deformation from engine startup and steady state may reduce the overall preload of the bolt, to the extent where there is no remaining bolt preload after engine shutdown

Methodology Applied

Scientific EffectCreep deformation resistance: Creep

Data Source

PatentUS11773748B2High temperature flange joint, exhaust diffuser and method for coupling two components in a gas turbine engine

Publication Date: 2023.10.03 SIEMENS ENERGY GLOBAL GMBH & CO KG

AI summary

A high temperature flange joint in a gas turbine engine includes a first flange formed on a first component abutting a second flange formed on a second component. The flange joint includes multiple adjacently spaced bolt connections. Each bolt connection includes a first spacer plate bearing against the first flange and a second spacer plate bearing against the second flange. First and second lock washers are provided that bear against the first and second spacer plates respectively. A bolt is inserted through the first and second flanges, the first and second spacer plates and the first and second lock washers. The bolt is preloaded to clamp the first flange to the second flange. Each spacer plate has a respective thickness and is sized to enhance a bearing surface in contact with the respective flange. Thereby, a bolt preload is maintained during operation of the gas turbine engine.