Core Compartment Venting to Reduce Bowed Rotor Restart Risk

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Solution Overview

Problem

Gas turbine engines experience bowed rotor conditions due to thermal expansion during shutdown, leading to non-uniform compressor clearances and performance issues upon restart, exacerbated by on-ground idle operations at busy airports.

Innovation Solution

Incorporating vent openings in the nacelle with fans to circulate cooling airflow through the core compartment, powered by a battery pack or generator, to equalize temperature distribution and reduce thermal gradients.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the engine operates at idle on the ground for extended periods, then the engine remains ready for operation, but thermal expansion causes bowed rotor conditions and uneven compressor clearances

Engineering Contradiction:

Improveengine readinessVSAvoidcompressor stability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The system performs preliminary cooling action during idle periods by activating fans to circulate air through the core compartment before the engine is shut down or before restart is required. This preliminary cooling equalizes temperature distribution and prevents thermal expansion from causing bowed rotor conditions, thereby maintaining compressor stability while keeping the engine ready for operation.

Inventive Principle:

Principle #10Preliminary action

2Loss of energy

If the engine is shut off after flight, then fuel burn and emissions are reduced, but thermal expansion causes deflection of components and bowed rotor conditions

Engineering Contradiction:

Improvefuel burnVSAvoidthermal expansion damage

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The system converts the harmful thermal expansion effect into a beneficial cooling opportunity. After engine shutdown, the fans continue to circulate air through the core compartment, utilizing the temperature differential to actively cool hot components and equalize temperature distribution. This transforms the post-shutdown cooling period into a beneficial process that prevents thermal expansion damage while minimizing fuel burn and emissions.

Inventive Principle:

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

Solution Approach 2:

The system performs preliminary cooling action during the shutdown period by activating fans to circulate air through the core compartment before the engine is completely cooled or before restart is required. This preliminary cooling equalizes temperature distribution and prevents thermal expansion from causing bowed rotor conditions, thereby maintaining compressor stability while keeping the engine ready for operation.

Inventive Principle:

Principle #10Preliminary action

3Device complexity

If cooling airflow is not circulated through the core compartment, then the structure remains simple, but asymmetric temperature distribution causes case bow and nonuniform compressor clearances

Engineering Contradiction:

Improvecooling system structureVSAvoidcompressor clearance uniformity

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The system utilizes the engine's own operational characteristics to provide cooling. The fans are positioned to utilize the natural temperature differential and airflow patterns within the engine core compartment, allowing the system to self-regulate temperature distribution without requiring complex external cooling mechanisms. This self-service approach maintains compressor clearance uniformity while keeping the cooling system structure relatively simple.

Inventive Principle:

Principle #25Self-service

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

Reduces the incidence of bowed rotor conditions by evenly cooling the core compartment, maintaining compressor stability and performance during engine restart.

Implementation Method 1

One or more fans are positioned at the one or more vent openings to urge the cooling airflow through the one or more vent openings to cool the core compartment

Methodology Applied

Scientific EffectForced Convection: Forced Convection

Implementation Method 2

circulate a cooling airflow through the core compartment

Methodology Applied

Scientific EffectConvection: Convection

Implementation Method 3

When this occurs thermal expansion may cause deflection of components within the engine, which may result in a 'bowed rotor' condition

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS12631144B2Core compartment vent during engine shutdown to reduced bowed rotor start

Publication Date: 2026.05.19 RTX CORP

AI summary

A core section and nacelle assembly of a gas turbine engine includes a compressor located at an engine central longitudinal axis, a core case enclosing the compressor, and a nacelle located radially outboard of the core case and defining a core compartment between the nacelle and the core case. One or more vent openings are located in the nacelle to circulate a cooling airflow through the core compartment, and one or more fans are positioned at the one or more vent openings to urge the cooling airflow through the one or more vent openings to cool the core compartment.