Gas Turbine Spool Configuration for Controlled Shaft Separation Testing

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Solution Overview

Problem

Gas turbine engines with dual-spool configurations face challenges in meeting containment performance requirements during shaft separation or decoupling, necessitating effective testing methodologies.

Innovation Solution

A spool configuration with a centering feature and tie shaft that applies a compressive load, allowing for controlled decoupling through the use of a pyrotechnic charge to release the load, facilitating shaft separation for testing purposes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If a dual-spool configuration is used in a gas turbine engine, then the engine can achieve improved performance and efficiency, but the complexity of meeting containment performance requirements during shaft separation increases

Engineering Contradiction:

Improveengine performanceVSAvoidcontainment testing complexity

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

The outer shaft assembly is divided into multiple shaft portions (first shaft portion and second shaft portion) that can be separately positioned and tested. This segmentation allows the shaft joint to be specifically designed with centering features, enabling controlled separation testing while maintaining overall engine performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A tie shaft is introduced as an intermediary component located radially inboard of the outer shaft assembly. The tie shaft applies axially compressive load to the outer shaft assembly and can be configured to accept pyrotechnic charges, serving as a mediator that enables controlled shaft separation for containment testing while preserving normal engine operation.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If shaft separation testing is required for containment performance verification, then safety requirements can be met, but the testing process becomes more difficult and complex

Engineering Contradiction:

Improvecontainment performanceVSAvoidtesting feasibility

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The shaft joint is pre-configured with centering features (outer diameter lip or inner diameter lip) that ensure proper radial alignment of shaft portions before separation. The tie shaft is also pre-positioned to apply compressive load, so that when pyrotechnic charges are detonated during testing, the shaft portions separate in a controlled manner along the longitudinal axis, making containment testing more feasible.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The mechanical state of the shaft assembly is changed from a loaded compressed state to a separated state through controlled detonation of pyrotechnic charges. This parameter change allows the shaft portions to separate along the longitudinal axis while maintaining proper radial alignment, enabling containment performance verification.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If the outer shaft assembly is designed to allow controlled separation, then containment testing can be performed, but the structural integrity during normal operation may be compromised

Engineering Contradiction:

Improvetesting capabilityVSAvoidshaft joint integrity

Core Design Contradiction:

Adaptability or versatilityVSStrength

Solution Approach 1:

The shaft joint transitions from a static connected state during normal operation to a dynamic separable state during testing. The centering features ensure that during normal operation, the shaft portions remain properly aligned and structurally sound. During testing, the tie shaft can be controlled to separate the shaft portions along the longitudinal axis while maintaining radial alignment, thus preserving structural integrity during operation while enabling testing capability.

Inventive Principle:

Principle #15Dynamics

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 ensures reliable containment performance testing by simulating shaft separation while minimizing axial resistance and vibratory loads, enabling efficient and controlled decoupling of shaft components.

Implementation Method 1

detonating the pyrotechnic charge thus separating the tie shaft, releasing the compressive load on the outer shaft assembly via detonating the pyrotechnic charge

Methodology Applied

Scientific EffectDetonation: Detonation

Data Source

PatentEP4613972A1Gas turbine engine configuration for containment testing

Publication Date: 2025.09.10 PRATT & WHITNEY CANADA CORP

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AI summary

A spool (22) of a gas turbine engine (10) includes an outer shaft assembly (40) positioned at and configured to rotate about an engine central longitudinal axis (A). The outer shaft assembly (40) is secured to one or more rotating components of the gas turbine engine (10). The outer shaft assembly (40) includes a first shaft portion (52), and a second shaft portion (54). The first shaft portion (52) axially overlaps the second shaft portion (54) at a shaft joint (56). A centering feature is positioned at the shaft joint (56) and is configured to radially center the second shaft portion (54) relative to the first shaft portion (52). A tie shaft (48) is concentric with and located radially inboard of the outer shaft assembly (40). The tie shaft (48) is configured to apply an axially compressive load on the outer shaft assembly (40).