Epicyclic Gearbox Support Layout for Large-Fan Vibration Isolation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Scaling up gas turbine engine components to accommodate a larger fan diameter for increased thrust is inefficient due to challenges in mounting the gearbox and fan shaft, requiring careful consideration of component properties to manage load transmission and vibration.
Innovation Solution
A gas turbine engine design featuring an epicyclic gearbox with specific radial bending and tilt stiffness ratios to support the fan shaft and gearbox, ensuring adequate isolation from load transmission and minimizing vibration, with a moment of inertia greater than or equal to 7.40×10^7 kgm^2 and radial bending stiffness to moment of inertia ratios within defined ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a larger fan diameter is used to increase thrust, then power output is improved, but device complexity worsens due to challenges in mounting the gearbox and fan shaft
Solution Approach 1:
The patent applies parameter changes by specifying precise stiffness-to-moment of inertia ratio ranges for the fan shaft and gearbox support. These parameter specifications enable the system to accommodate larger fan diameters while maintaining manageable mounting complexity through controlled structural properties.
Solution Approach 2:
The patent employs dynamics by allowing controlled flexibility in the fan shaft and gearbox support through specified stiffness ratios. This dynamic approach enables the mounting structure to adapt to the increased demands of larger fans while maintaining operational reliability.
2Strength
If the radial bending stiffness of the fan shaft is increased to support larger fans, then strength is improved, but vibration isolation worsens due to increased load transmission to the gearbox
Solution Approach 1:
The patent resolves this contradiction through parameter changes by defining specific ratio ranges for radial bending stiffness to moment of inertia. This approach allows the fan shaft to have sufficient strength for larger fans while the controlled ratio prevents excessive vibration transmission to the gearbox.
Solution Approach 2:
The patent applies dynamics by implementing a flexible yet controlled mounting system. The specified stiffness ratios create a dynamic balance that allows the fan shaft to be strong enough for large fans while maintaining vibration isolation properties through controlled flexibility.
3Power
If the moment of inertia of the fan is increased for larger fan diameter, then power output is improved, but the radial bending stiffness requirement worsens to maintain adequate vibration isolation
Solution Approach 1:
The patent applies parameter changes by specifying the radial bending stiffness to moment of inertia ratio within defined ranges. This approach allows the system to accommodate fans with higher moment of inertia (larger diameter for increased power) while maintaining appropriate stiffness levels through the ratio control, preventing excessive strength requirements.
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 effectively isolates the gearbox from load transmission, reducing the risk of excessive vibration and ensuring reliable operation by maintaining stiffness within specified ranges, thus enhancing the engine's efficiency and performance.
Implementation Method 1
a radial bending stiffness to moment of inertia ratio of: is greater than or equal to 2.5×10−3
Implementation Method 2
the gearbox being an epicyclic gearbox comprising a sun gear, a plurality of planet gears, a ring gear, and a planet carrier
Implementation Method 3
a fan located upstream of the engine core, the fan comprising a plurality of fan blades
Data Source
AI summary
A gas turbine engine (10) for an aircraft comprising: an engine core (11) comprising a turbine (19), a compressor (14), and a core shaft (26) connecting the turbine to the compressor; a fan (23) located upstream of the engine core, the fan comprising a plurality of fan blades; a gearbox (30) that receives an input from the core shaft (26) and outputs drive to the fan so as to drive the fan at a lower rotational speed than the core shaft, the gearbox (30) being an epicyclic gearbox (30) comprising a sun gear (28), a plurality of planet gears (32), a ring gear (38), and a planet carrier (34) arranged to have the plurality of planet gears (32) mounted thereon; and a gearbox support (40) arranged to at least partially support the gearbox within the engine. The gearbox (30) has a cross sectional area, the cross sectional area being greater than or equal to 2.4×10−1 m2; anda first gearbox support strength ratio of:thetorsionalstrengthofthegearboxsupport(40)theradialbendingstiffnessofthegearboxsupport(40)×thecrosssectionalareaofthegearboxis greater than or equal to 7.0×10−3. A planet gear spacing angle in radians (β) is defined as 2π/N, where N is the number of planet gears (32). A second gearbox support strength ratio of:thetorsionalstrengthofthegearboxsupport(40)thetiltstiffnessofthegearboxsupport(40)×theplanetgearspacingangle(β)is greater than or equal to 1.0×10−1.