Variable Pitch Fan Blade Mount System for Gas Turbine Engines
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Solution Overview
Problem
Existing fan systems in gas turbine engines face limitations in pitch control due to design space and weight constraints, particularly in propeller-driven aircraft, where traditional actuator and counterweight methods are inefficient.
Innovation Solution
A variable-pitch fan system with a mount system comprising inner and outer bearing units and a retention plate, allowing for radial movement and misalignment tolerance, coupled with a pitch controller using a spline shaft and rotator control, enables individual fan blade pivot and replacement while minimizing the fan disk size and component count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional actuators and counterweights are used for propeller blade pitch control, then pitch control is achieved, but design space and weight allocations are limited
Solution Approach 1:
The propeller blade is divided into separate functional components: the blade body, the pitch control mechanism, and the hub connection. This segmentation allows the pitch control mechanism to be optimized independently from the blade structure, reducing overall weight while maintaining control functionality.
Solution Approach 2:
The patent implements dynamic pitch control through a mechanism that allows the blade pitch angle to change during operation. The pitch control system uses a combination of fixed and movable components that enable continuous adjustment of blade pitch, improving ease of operation without requiring heavy static structures.
2Ease of operation
If traditional actuators and counterweights are used for propeller blade pitch control, then pitch control is achieved, but design space is limited
Solution Approach 1:
The pitch control mechanism is nested within the propeller hub structure, with components arranged concentrically around the central axis. The actuator, bearing units, and retention mechanisms are positioned within the hub's internal volume, maximizing utilization of available design space without increasing external dimensions.
Solution Approach 2:
The patent utilizes the radial dimension of the hub structure to accommodate pitch control components. By arranging mechanisms in the radial direction rather than only in planar dimensions, the design maximizes use of three-dimensional space, freeing up design space for other system requirements.
3Reliability
If bearing units are arranged around the fan blade shank, then misalignment tolerance is improved, but component count increases
Solution Approach 1:
The patent combines multiple bearing units into a single integrated bearing assembly that surrounds the fan blade shank. This merged structure provides misalignment tolerance in multiple directions simultaneously, achieving the same reliability benefit as multiple separate bearings but with reduced component count and simplified installation.
Solution Approach 2:
The bearing assembly is designed to perform multiple functions: supporting radial loads, accommodating misalignment, and enabling pitch rotation. This multi-functional design eliminates the need for separate components for each function, reducing overall component count while maintaining reliability.
4Ease of repair
If the retention plate is configured to allow radial outward movement of the fan blade, then ease of repair is improved, but structural complexity increases
Solution Approach 1:
The retention plate is designed with extractable or removable features that allow the fan blade to be easily extracted from the hub for replacement. The plate includes quick-release mechanisms or detachable fasteners that enable blade removal without disassembling the entire mount system, improving ease of repair while maintaining structural integrity during operation.
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
Enables efficient thrust variation and fan blade replacement on-wing, reducing the hub-to-tip ratio and component count, thereby improving pitch control and maintenance accessibility without increasing engine size or weight.
Implementation Method 1
The inner bearing unit includes a roller bearing unit configured to bear radial force loads relative to the pitch axis
Implementation Method 2
The outer bearing unit includes a spherical tapered roller bearing unit configured to bear axial and radial force loads
Implementation Method 3
The outer bearing unit is configured to tolerate misalignment of the shank of the fan blade in the disk aperture
Data Source
AI summary
A gas turbine engine includes a fan having a plurality of fan blades configured to rotate about a central axis of the gas turbine engine. Each fan blade is configured to pivot about a pitch axis that extends radially away from the central axis to vary a pitch of the fan blade.