Fan Hub Actuation Layout for Variable-Pitch Turbofan Blades
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Solution Overview
Problem
The challenge of designing a compact and efficient fan actuation system for turbofan engines with variable pitch fan blades is exacerbated by the need to accommodate a larger number of blades and higher load requirements, which is not directly addressed by scaling up turboprop engine designs due to differences in inlet geometry and available space.
Innovation Solution
A fan actuation system for turbofan engines incorporating a gearbox assembly with a coaxial in-line configuration and a compact design that includes a fan actuation system within a fan hub, utilizing hydraulic actuators to adjust pitch collectively, and considering unique space constraints and higher load demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fan actuation system is designed for turbofan engines with variable pitch fan blades, then the system must accommodate higher load requirements and more blades, but this increases the complexity and size of the actuation system
Solution Approach 1:
The fan actuation system is divided into multiple independent actuators, each responsible for specific fan blades. This segmentation allows the system to handle higher load requirements through parallel processing while keeping individual component complexity manageable. Each actuator can be optimized for its specific function rather than designing a monolithic system to handle all loads.
Solution Approach 2:
The actuation system utilizes a nested configuration where actuators are integrated within the fan hub structure. The coaxial in-line gearbox assembly is nested within the fan hub, and actuators are positioned within the available space between the fan blades and hub structure. This nesting approach reduces overall system volume and complexity by efficiently utilizing internal space.
2Power
If the fan actuation system is designed to accommodate more fan blades and higher loads, then the system capacity increases, but the available space in the fan hub is insufficient
Solution Approach 1:
The system transitions from a radial arrangement to a coaxial in-line configuration, utilizing the axial dimension instead of radial space. The gearbox assembly is arranged coaxially with the fan shaft, and actuators are positioned along the axial path within the fan hub. This dimensional change allows the system to accommodate higher power requirements without increasing the radial footprint, effectively utilizing the available axial and radial space in three-dimensional configuration.
3Volume of moving object
If a coaxial in-line gearbox assembly is used in the fan hub, then space efficiency is improved, but the design must account for unique space constraints and higher load demands
Solution Approach 1:
The coaxial in-line gearbox assembly is designed to serve multiple functions: it provides power transmission to the fan blades, accommodates the actuators for pitch control, and utilizes the available space efficiently. This multi-functional design eliminates the need for separate components for each function, reducing overall system volume while maintaining ease of manufacture through integrated construction. The universal design approach allows the same assembly to handle both space constraints and higher load demands.
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 solution provides a compact and efficient fan actuation system that meets the higher loading and space requirements of turbofan engines, ensuring reliable operation and space efficiency for variable pitch fan blades.
Implementation Method 1
A hydraulic actuator may be used to rotate the fan blade about the pitch axis
Data Source
AI summary
A turbofan engine for an aircraft includes a fan and a fan actuation system. The fan has a plurality of fan blades coupled to a fan shaft having one or more fan bearings. The fan blades are rotatable about a pitch axis. The fan actuation system is disposed within a fan hub and includes one or more actuators for rotating the fan blades about the pitch axis and one or more radial thrust bearings. The fan actuation system is characterized by a fan actuation system length envelope in a range from 8.5 to 24 and given byNFB×DFTLAXIAL×(RTBNFB).NFB is a number of the fan blades, DFT is a fan tip diameter of the fan blades, RTB is a thrust bearing radius of the radial thrust bearings, and LAXIAL is an axial length from a fan hub tip to the fan bearings.