Variable Area Fan Nozzle for Gas Turbine Engine Drag Reduction

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Solution Overview

Problem

Conventional gas turbine engines face inefficiencies in thrust production and drag during engine-out conditions due to insufficient fan bypass flow area, leading to flow spillage and increased drag, particularly at cruise conditions.

Innovation Solution

A gas turbine engine with a variable geometry fan exit guide vane system and a fan variable area nozzle that allows for axial movement and rotation of fan exit guide vanes to adjust the fan bypass flow path and nozzle exit area, controlled by a gear system and a controller to optimize fan pressure ratio and bypass ratio, reducing drag and noise.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the fan nacelle diameter is increased to provide sufficient bypass flow area during engine-out conditions, then flow spillage and drag are reduced during engine-out conditions, but the nacelle diameter becomes larger than necessary during normal cruise conditions resulting in non-optimal drag

Engineering Contradiction:

Improveengine-out condition performanceVSAvoidcruise condition efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent applies a variable geometry fan exit guide vane system that can dynamically adjust the bypass flow area. The fan exit guide vanes are rotatable about an axis of rotation to vary the fan bypass flow path area, allowing the engine to optimize performance for different operating conditions including engine-out scenarios and normal cruise conditions, thereby resolving the contradiction between reliability during engine-out conditions and productivity during cruise.

Inventive Principle:

Principle #15Dynamics

2Device complexity

If a fixed geometry fan exit guide vane system is used, then the device complexity is reduced, but the adaptability to different flight conditions including engine-out scenarios is limited

Engineering Contradiction:

Improvefan exit guide vane systemVSAvoidperformance across flight conditions

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent implements a variable geometry fan exit guide vane system where the vanes can rotate to change the bypass flow area. This dynamic capability allows the system to adapt to different flight conditions including engine-out scenarios, achieving high versatility while maintaining relatively simple mechanical implementation through rotational movement about a fixed axis.

Inventive Principle:

Principle #15Dynamics

3Productivity

If the fan bypass flow path area is minimized for optimal cruise performance, then drag during cruise conditions is reduced, but flow spillage increases during engine-out conditions

Engineering Contradiction:

Improvecruise condition efficiencyVSAvoidengine-out condition performance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The variable geometry fan exit guide vane system allows the bypass flow area to be dynamically adjusted. During normal cruise conditions, the vanes can be positioned to minimize the flow path area for optimal drag performance, while during engine-out conditions, the vanes can be rotated to increase the flow area and prevent flow spillage, thus resolving the contradiction between cruise efficiency and engine-out reliability.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS8459035B2Gas turbine engine with low fan pressure ratio

Publication Date: 2013.06.11 RTX CORP

AI summary

A turbofan engine includes a fan variable area nozzle axially movable relative to the fan nacelle to vary a fan nozzle exit area and adjust a pressure ratio of the fan bypass airflow during engine operation.