Fan Outlet Guide Vane Geometry for Shock Buffet Reduction

Solution Overview

Problem

Gas turbine engines with lower specific thrust and higher flows face challenges due to larger diameter fan outlet guide vane (FOGV) rings and nacelle, leading to increased nacelle drag, weight, and reduced FOGV stiffness, which are addressed by optimizing the space-chord ratio of outlet guide vanes to reduce shock-induced buffet.

Innovation Solution

The space-chord ratio of outlet guide vanes is reduced to less than 0.72 at 50% of the span length and maintained within specific ranges across the span, and the ratio at 70% of the span length is increased relative to 50% to reduce local flow speed and minimize shock-induced buffet.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If larger diameter fan outlet guide vane rings and nacelle are used to handle higher flows, then the engine can achieve lower specific thrust and higher flows for a given thrust, but this leads to higher nacelle drag and weight

Engineering Contradiction:

Improveflow rateVSAvoidnacelle weight

Core Design Contradiction:

ProductivityVSWeight of stationary object

Solution Approach 1:

The patent optimizes the space-chord ratio parameter of the outlet guide vanes (specifically setting it to less than 0.72 at 50% span length) to reduce shock-induced buffet and improve flow characteristics, allowing for more efficient flow management without increasing nacelle diameter and thereby avoiding increased weight and drag

Inventive Principle:

Principle #35Parameter changes

2Productivity

If larger diameter fan outlet guide vane rings and nacelle are used to handle higher flows, then the engine can achieve lower specific thrust and higher flows for a given thrust, but this leads to higher nacelle drag

Engineering Contradiction:

Improveflow rateVSAvoidnacelle drag

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The patent optimizes the space-chord ratio parameter of the outlet guide vanes (specifically setting it to less than 0.72 at 50% span length) to reduce shock-induced buffet and improve flow characteristics, allowing for more efficient flow management without increasing nacelle diameter and thereby avoiding increased drag and energy loss

Inventive Principle:

Principle #35Parameter changes

3Productivity

If larger diameter fan outlet guide vane rings are used to handle higher flows, then the engine can achieve lower specific thrust and higher flows for a given thrust, but this results in lower FOGV stiffness

Engineering Contradiction:

Improveflow rateVSAvoidFOGV stiffness

Core Design Contradiction:

ProductivityVSStrength

Solution Approach 1:

The patent optimizes the space-chord ratio parameter of the outlet guide vanes (specifically setting it to less than 0.72 at 50% span length) to reduce shock-induced buffet and improve flow characteristics, allowing for more efficient flow management without increasing nacelle diameter and thereby avoiding increased weight and drag

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12497894B2Gas turbine engine

Publication Date: 2025.12.16 ROLLS ROYCE PLC

AI summary

A gas turbine engine for an aircraft comprises: an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor; a fan located upstream of the engine core, the fan comprising a plurality of fan blades; a bypass duct delimited by a bypass duct inner wall and a bypass duct outer wall and located radially outwardly from the engine core and downstream of the fan; and an outlet guide vane assembly, located within the bypass duct and, comprising a plurality of outlet guide vanes distributed circumferentially within the bypass duct, each outlet guide vane extending radially along a span between the bypass duct inner wall and the bypass duct outer wall, wherein a space-chord ratio of at least one outlet guide vane, at 50% of the span length from the bypass duct inner wall, is less than 0.72.