Gas Turbine Fan Outlet Guide Vane Root Position Ratio
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Solution Overview
Problem
Large gas turbine engines face structural challenges due to increased bending loads and stress as a result of larger fan diameters, which can lead to deformation and reduced efficiency, particularly exacerbated by the rearward movement of fan outlet guide vanes.
Innovation Solution
The gas turbine engine design incorporates specific relative component positions and ratios, such as the fan OGV root position ratio, fan diameter, and flange connection positions, to increase engine core stiffness and manage bending loads effectively, including a gearbox that reduces fan rotational speed and optimizes fan blade mass distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the fan diameter is increased, then the engine can provide greater thrust and accommodate larger aircraft, but the bending loads on the engine core and supporting components are deleteriously increased
Solution Approach 1:
The patent relocates the first flange connection from a conventional position to a position in the second compressor stage, utilizing the axial dimension to create a more favorable load distribution. This dimensional repositioning allows the bending loads to be better managed by the engine core structure while maintaining the large fan diameter for enhanced thrust capability.
Solution Approach 2:
The patent changes the axial position parameter of the first flange connection to occur at the second compressor stage rather than at the first compressor stage. This parameter change fundamentally alters the structural load path and enables the engine core to better withstand the bending loads generated by the large fan diameter.
2Power
If the fan size is increased, then greater thrust is achieved, but the bending loads on the engine core increase significantly
Solution Approach 1:
The patent utilizes the axial dimension by positioning the first flange connection at the second compressor stage, creating a more optimal structural arrangement that reduces bending stress on the engine core while maintaining the large fan diameter necessary for high thrust output.
3Adaptability or versatility
If fan outlet guide vanes are positioned rearward, then certain design constraints are satisfied, but the bending loads on the engine core are exacerbated
Solution Approach 1:
The patent compensates for the rearward positioning of fan outlet guide vanes by utilizing the axial dimension to reposition the first flange connection to the second compressor stage. This dimensional adjustment creates a more favorable structural configuration that reduces the exacerbation of bending loads while maintaining compliance with design constraints.
Data Source
Figure 1~2
Figure 3A~3B
Figure 4A~4C
AI summary
A gas turbine engine (10) for an aircraft comprises an engine core (11); a fan (23) located upstream of the engine core (11) and having a fan diameter (112); a nacelle (21) surrounding the engine core (11) and defining a bypass duct (22) between the engine core (11) and the nacelle (21); a first (14) and a second compressor (15); an outer core casing (76) comprising a flange connection (60) and a fan outlet guide vane (OGV) (58) extending radially across the bypass duct (22), the fan OGV (58) having a radially inner edge (58a) and a radially outer edge (58b), wherein an axial midpoint of the radially inner edge (58a) is defined as the fan OGV root centrepoint (58a). A fan OGV root position ratio of: axial distance (108) between flange connection and fan OGV root centrepoint vs. flange radius (104) is equal to or less than 2.6.