Fan Outlet Guide Vane Root Position for Gas Turbine Core Stiffness
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Solution Overview
Problem
Large gas turbine engines face structural challenges due to increased bending loads and stiffness issues, particularly with larger fan diameters, which can lead to deformation and efficiency losses.
Innovation Solution
The gas turbine engine design incorporates specific relative component positions and configurations, including a first flange connection downstream of the axial midpoint between compressor aerofoils, a gearbox-driven fan with a gear ratio between 3.1 and 4.0, and optimized fan blade and core casing geometries to manage bending loads and improve stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the fan size of a gas turbine engine is increased, then the engine's thrust and efficiency are improved, but bending loads on the engine core are deleteriously increased
Solution Approach 1:
The patent applies parameter changes by optimizing the axial position of the first flange connection relative to the compressor aerofoils. By positioning the flange connection at a specific axial location (downstream of the axial midpoint between the trailing edge of the most downstream aerofoil of the first compressor and the leading edge of the most upstream aerofoil of the second compressor), the design changes the structural distribution of bending loads. This parameter optimization allows the engine to accommodate larger fan sizes while managing the increased bending loads through improved structural configuration rather than simply increasing core size.
2Productivity
If the fan diameter is increased, then the engine's bypass ratio and fuel efficiency are improved, but structural stiffness and deformation resistance are worsened
Solution Approach 1:
The patent optimizes structural stiffness through parameter changes in the flange connection positioning and core casing configuration. By setting the first flange connection at a specific axial position and defining its radius relative to the gas path radius (with specific ratio ranges), the design enhances the structural stiffness of the engine core. This allows the engine to maintain adequate deformation resistance even with increased fan diameters that improve bypass ratio and fuel efficiency.
Solution Approach 2:
The patent addresses structural stiffness by transitioning from a one-dimensional scaling approach to a multi-dimensional structural optimization. Instead of simply increasing all dimensions proportionally, the design specifies particular dimensional relationships (flange radius to gas path radius ratios, axial positions relative to compressor stages) that create an optimized three-dimensional structural configuration. This dimensional optimization maintains stiffness characteristics while accommodating larger fan diameters for improved fuel efficiency.
3Strength
If the engine core is redesigned to accommodate larger fan sizes, then bending load capacity is improved, but device complexity and manufacturing difficulty are increased
Solution Approach 1:
The patent reduces design complexity by applying parameter changes rather than complete redesign. Instead of fundamentally reconfiguring the engine core, the invention optimizes specific parameters: the axial position of the first flange connection, its radius relative to the gas path, and its position relative to compressor stages. These targeted parameter optimizations achieve improved bending load capacity while maintaining the existing engine core architecture, thereby avoiding the complexity and manufacturing difficulties associated with complete redesigns.
Data Source
AI summary
A gas turbine engine includes an engine core, a fan located upstream of the engine core, a nacelle surrounding the engine core and defining a bypass duct, and a fan outlet guide vane (OGV) extending radially across the bypass duct between an outer surface of the engine core and an inner surface of the nacelle. The engine core includes a compressor system, and an outer core casing surrounding the compressor system and including a first flange connection arranged to allow separation of the outer core casing at an axial position of the first flange connection. An axial midpoint of a radially inner edge of the fan OGV is defined as the fan OGV root centrepoint. A fan OGV root position to fan diameter ratio of:anaxialdistancebetweenthefirstflangeconnectionandthefanOGVrootcentrepointthefandiameteris equal to or less than 0.33.