Double-Wall Turbine Shaft Plug Thermal Management

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Solution Overview

Problem

Gas turbine engines operating at higher temperatures face issues with shaft plug interference fits becoming loose, seal compression loosening, and non-metallic seals experiencing damage due to heat, leading to leaks and potential auto-ignition and oil coking issues.

Innovation Solution

A two-layer (double-wall) shaft plug design is introduced, featuring a forward section and an aft section separated by a gap. The aft section is cooled by oil flow, while the gap thermally isolates the forward section, allowing it to operate at a higher temperature and maintain a tight interference fit with the shaft.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a single-wall shaft plug design is used, then the structure is simple and easy to manufacture, but the plug cannot withstand higher temperatures causing interference fit to loosen and seals to damage

Engineering Contradiction:

Improvetemperature withstanding capabilityVSAvoidplug structure complexity

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The shaft plug is divided into two separate walls (first wall and second wall) with a gap between them, creating a double-wall structure. This segmentation allows each wall to operate at different temperatures, with the first wall exposed to higher temperatures and the second wall cooled by oil flow, thereby resolving the contradiction between temperature withstanding capability and structural simplicity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The first wall is positioned within the inner diameter of the second wall, creating a nested configuration where the cooled second wall contains the hotter first wall. This nesting arrangement allows the plug to maintain structural integrity while withstanding higher temperatures through thermal isolation provided by the gap between the walls.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Temperature

If the plug is cooled by oil flow, then the seal compression is maintained, but the forward section cannot operate at higher temperatures

Engineering Contradiction:

Improveoperating temperature of forward sectionVSAvoidseal integrity

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The plug is segmented into two walls separated by a gap, allowing differential thermal management. The first wall can operate at higher temperatures while the second wall is cooled by oil flow to maintain seal compression, resolving the contradiction between operating temperature and seal integrity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The gap between the first and second walls acts as a thermal intermediary, isolating the forward section (first wall) from the cooling oil flow that contacts the aft section (second wall). This intermediary space allows the forward section to operate at higher temperatures while the aft section maintains conditions for seal integrity.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Temperature

If a non-metallic seal is used, then the seal is flexible and easy to install, but the seal experiences damage due to heat at higher operating temperatures

Engineering Contradiction:

Improveheat resistanceVSAvoidseal damage from heat

Core Design Contradiction:

TemperatureVSObject-affected harmful factors

Solution Approach 1:

The seal system is segmented into two zones: the forward section where the first wall operates at higher temperatures, and the aft section where the second wall is cooled by oil flow. This segmentation protects the non-metallic seal from excessive heat while maintaining the flexibility and ease of installation advantages of non-metallic materials.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The oil cooling flow, which could potentially harm the non-metallic seal through direct contact, is instead used beneficially to cool the second wall and protect the seal from heat damage. The cooling system converts a potential harmful effect (heat) into a beneficial protective effect, allowing the non-metallic seal to operate reliably at higher overall operating temperatures.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 double-wall plug design enhances the shaft plug's ability to withstand higher temperatures, maintaining a secure interference fit and preventing seal damage, thereby reducing the risk of leaks, auto-ignition, and oil coking.

Implementation Method 1

the gap thermally isolates the forward section, allowing it to operate at a higher temperature

Methodology Applied

Scientific EffectThermal insulation: Thermal Insulation

Implementation Method 2

The aft section is cooled by oil flow

Methodology Applied

Scientific EffectConvection cooling: Convection

Implementation Method 3

maintain a tight interference fit with the shaft

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS12203412B2Turbine engine shaft plug

Publication Date: 2025.01.21 RTX CORP

AI summary

A gas turbine engine has a shaft having an inner diameter surface. A plug is mounted in the shaft. An oil nozzle is positioned to direct a flow of oil to an interior of the shaft. The plug has: a first section; a second section having an outer diameter periphery; and an axial gap between the first section and the second section.