Geared Turbofan Gearbox Support for Large-Fan Vibration Isolation
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Solution Overview
Problem
Scaling up gas turbine engine components to accommodate a larger fan diameter leads to inefficiencies and mounting challenges, particularly in supporting the gearbox and fan shaft within the engine.
Innovation Solution
A gas turbine engine design that includes an epicyclic gearbox supported by a gearbox support, with specific ratios of radial bending stiffness to moment of inertia and tilt stiffness to moment of inertia, ensuring efficient operation and mounting of the fan and gearbox.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a larger fan diameter is used to increase thrust and efficiency, then power output is improved, but mounting and supporting the gearbox and fan shaft becomes more difficult
Solution Approach 1:
The gearbox support structure is divided into multiple components: a support structure, a fan shaft, and a gearbox. This segmentation allows each component to be optimized independently for its specific function while simplifying the overall mounting process for the larger fan system.
Solution Approach 2:
The fan shaft acts as an intermediary component between the gearbox and the fan. It transmits power while providing the necessary mechanical connection and support, thereby simplifying the mounting arrangement for the larger fan diameter configuration.
2Volume of moving object
If gearbox and fan shaft components are scaled up to accommodate larger fan, then fan diameter is increased, but efficiency decreases due to mounting problems
Solution Approach 1:
The patent specifies precise parameter ranges for the fan shaft's radial bending stiffness (2.5×10^-2 to 6.0 Nkg^-1m^-1mm^-2) and tilt stiffness (0.06 to 0.48 Nkg^-1m^-1mm^-2) relative to the fan's moment of inertia. These parameter changes ensure optimal performance and efficiency while accommodating the larger fan diameter.
3Strength
If fan shaft and gearbox support stiffness is increased to handle larger fan, then structural integrity is improved, but vibrations and damaging loads to gearbox increase
Solution Approach 1:
The patent optimizes the stiffness parameters within specific ranges rather than maximizing them. The radial bending stiffness ratio (2.5×10^-2 to 6.0 Nkg^-1m^-1mm^-2) and tilt stiffness ratio (0.06 to 0.48 Nkg^-1m^-1mm^-2) are carefully selected to provide sufficient structural integrity while avoiding excessive stiffness that would transmit damaging vibrations to the gearbox.
4Stability of the object's composition
If fan shaft stiffness is increased to support larger fan, then moment of inertia effects are reduced, but gearbox isolation from damaging loads deteriorates
Solution Approach 1:
The patent establishes an optimal range for the fan shaft's radial bending stiffness to moment of inertia ratio (2.5×10^-2 to 6.0 Nkg^-1m^-1mm^-2) and tilt stiffness to moment of inertia ratio (0.06 to 0.48 Nkg^-1m^-1mm^-2). These parameter changes ensure the fan shaft provides sufficient stability while effectively isolating the gearbox from damaging loads through controlled flexibility.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design achieves efficient operation by isolating the gearbox from damaging loads, reducing vibrations, and maintaining structural integrity, thereby enhancing the engine's reliability and performance.
Implementation Method 1
a radial bending stiffness to moment of inertia ratio of: (the radial bending stiffness of the fan shaft at the output of the gearbox)/(the moment of inertia of the fan) is greater than or equal to 2.5×10^-2 Nkg^-1m^-1mm^-2
Implementation Method 2
a tilt stiffness to moment of inertia ratio of: (the tilt stiffness of the fan shaft at the output of the gearbox)/(the moment of inertia of the fan) is greater than or equal to 4.0×10^-4 Nmrad^-1kg^-1mm^-2
Implementation Method 3
the gearbox being an epicyclic gearbox comprising a sun gear, a plurality of planet gears, a ring gear, and a planet carrier arranged to have the plurality of planet gears mounted thereon
Implementation Method 4
a fan shaft extending from the output of the gearbox to an input to the fan
Data Source
AI summary
Gas turbine engine for aircraft includes: an engine core including a turbine, compressor, and core shaft connecting the turbine to the compressor; a fan located upstream of the core; a gearbox; and a gearbox support arranged to at least partially support the gearbox. The fan has a mass in a range of 150 kg to 1200 kg. A moment of inertia of the fan is greater than or equal to 7.40×107 kgmm2. A radial bending stiffness to moment of inertia ratio of:the radial bending stiffness of at least one of the fan shaft at the output of the gearbox and the gearbox supportthe moment of inertia of the fanmay be greater than or equal to 2.5×10−2 Nkg−1m−1mm−2. A tilt stiffness to moment of inertia ratio of:the tilt stiffness of at least one of the fan shaft at the output of the gearbox and the gearbox supportthe moment of inertia of the fanmay be greater than or equal to 4.0×10−4 Nmrad−1kg−1mm−2.