Three-Stream Gas Turbine Core Cowl Layout for Fan Diameter Packaging

Solution Overview

Problem

Conventional turbofan engine designs face challenges in increasing fan diameter to improve fuel efficiency while maintaining propulsive efficiency and reducing engine weight, particularly due to the limitations imposed by the outer nacelle and axial length, which restricts the size and packaging of engine accessories.

Innovation Solution

A three-stream gas turbine engine design with an unducted primary fan and a ducted secondary fan, along with a third stream, allows for a larger fan diameter, reducing the core engine's axial length and enabling efficient packaging of accessories within the core cowl, while maintaining propulsive efficiency and facilitating easier access for maintenance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the fan diameter is increased to maintain efficient thrust and propulsive efficiency, then the propulsive efficiency is improved, but the engine weight and installation complexity increase

Engineering Contradiction:

Improvepropulsive efficiencyVSAvoidengine weight

Core Design Contradiction:

Loss of energyVSWeight of moving object

Solution Approach 1:

The engine is divided into three separate air streams (core stream, mid stream, and bypass stream) that operate independently through different paths. The core stream passes through the core engine, the mid stream is generated by the secondary fan, and the bypass stream is generated by the primary fan, allowing each component to be optimized for its specific function while reducing overall weight

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a third air stream dimension alongside the traditional core and bypass streams. This three-stream configuration allows the engine to achieve high propulsive efficiency with a larger fan diameter by utilizing the additional mid stream, thereby reducing the weight penalty associated with conventional two-stream designs

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Loss of energy

If the fan diameter is increased to maintain efficient thrust, then the propulsive efficiency is improved, but the installation complexity increases

Engineering Contradiction:

Improvepropulsive efficiencyVSAvoidinstallation complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The engine is divided into three separate air streams (core stream, mid stream, and bypass stream) that operate independently through different paths. The core stream passes through the core engine, the mid stream is generated by the secondary fan, and the bypass stream is generated by the primary fan, allowing each component to be optimized for its specific function while reducing overall weight

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a third air stream dimension alongside the traditional core and bypass streams. This three-stream configuration allows the engine to achieve high propulsive efficiency with a larger fan diameter by utilizing the additional mid stream, thereby reducing the weight penalty associated with conventional two-stream designs

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Weight of moving object

If the axial length of the core engine is reduced, then the overall weight is reduced, but the packaging space for accessories decreases

Engineering Contradiction:

Improveengine weightVSAvoidpackaging space

Core Design Contradiction:

Weight of moving objectVSVolume of stationary object

Solution Approach 1:

The patent introduces a third air stream dimension alongside the traditional core and bypass streams. This three-stream configuration allows the engine to achieve high propulsive efficiency with a larger fan diameter by utilizing the additional mid stream, thereby reducing the weight penalty associated with conventional two-stream designs

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The engine is divided into three separate air streams (core stream, mid stream, and bypass stream) that operate independently through different paths. The core stream passes through the core engine, the mid stream is generated by the secondary fan, and the bypass stream is generated by the primary fan, allowing each component to be optimized for its specific function while reducing overall weight

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS12631146B2Gas turbine engine

Publication Date: 2026.05.19 GENERAL ELECTRIC CO

AI summary

A gas turbine engine defines an axial direction and a radial direction and comprises a turbomachine having an unducted primary fan, a core engine a combustor casing enclosing a combustor and defining an outer surface, a core cowl surrounding at least a portion of the core engine. The outer surface of the core cowl defines a peak cowl diameter (D) in the radial direction, and the outer surface of the combustor casing defines a maximum combustor casing diameter (d) along the radial direction. The core engine defines an overall core axial length (L) along the axial direction and an under-core cowl axial length (L1) along the axial direction. The gas turbine engine defines a core cowl diameter ratio (CDR) equal to the peak cowl diameter (D) divided by the maximum combustor casing diameter (d) and a core cowl length ratio (CLR) equal to the under-core cowl axial length (L1) divided by the overall core axial length (L). The CDR is between 2.7 and 3.5 and the CLR is between 0.25 and 0.50.