Segmented Variable Fan Outlet Guide Vane Gear Assembly
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Solution Overview
Problem
Gas turbine engine fan blades experience operability issues due to variations in intake airflow and pressure fluctuations within the inlet and bypass ducts.
Innovation Solution
A fan assembly with a fan duct and a fan comprising rotating blades, along with an outlet guide vane assembly that includes a variable leading edge outlet guide vane with a tip segment and a hub segment, both capable of independent rotation via gear assemblies and actuation assemblies to adjust the direction of fan exit air and reduce incidence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed outlet guide vane is used, then the structure is simple, but it cannot adapt to variations in intake airflow and pressure fluctuations
Solution Approach 1:
The outlet guide vane is transformed from a fixed structure to a dynamic, adjustable structure. The leading edge portion can rotate about a leading edge pitch axis to change its pitch angle, allowing the vane to adapt to varying airflow conditions. This dynamic adjustment capability enables the system to respond to intake airflow variations and pressure fluctuations while maintaining structural feasibility through a defined rotation axis and gear mechanism.
Solution Approach 2:
The outlet guide vane is divided into distinct segments: a fixed aft portion and a variable leading edge portion that can rotate independently. This segmentation allows the leading edge to adjust to airflow variations while the aft portion remains structurally stable. The gear assembly further segments the adjustment mechanism into controllable components that can be actuated independently to achieve the desired pitch angle changes.
2Adaptability or versatility
If a variable pitch outlet guide vane is implemented, then adaptability to distorted fan exit air is improved, but the device complexity increases due to additional actuation mechanisms
Solution Approach 1:
A gear assembly is introduced as an intermediary mechanism between the actuation rod and the leading edge portion. The gear assembly translates the linear or rotational motion of the actuation rod into precise rotational movement of the leading edge about the pitch axis. This intermediary mechanism provides controlled, incremental adjustment of the pitch angle, enabling the vane to match distorted fan exit air patterns while keeping the actuation system manageable through mechanical advantage and controlled motion transmission.
3Reliability
If the leading edge portion is made rotatable to adjust pitch angle, then incidence reduction is achieved, but the structural complexity and manufacturing difficulty increase
Solution Approach 1:
The leading edge portion is designed to rotate in discrete, controlled increments rather than continuous movement. The gear assembly with defined teeth engages with corresponding gear teeth on the leading edge, allowing periodic adjustment to specific pitch angles. This periodic action simplifies manufacturing by defining specific, repeatable positions rather than requiring continuous variable geometry, while still achieving the reliability needed to reduce incidence under varying airflow conditions.
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 effectively adjusts the direction of fan exit air, reducing incidence and improving fan operability and performance by matching the vane to distorted fan exit air, thereby enhancing thrust and efficiency.
Implementation Method 1
a first gear assembly coupled to the first actuation rod and in engagement with the first plurality of gear teeth of the first tip segment, and a second gear assembly coupled to the first actuation rod and in engagement with the second plurality of gear teeth of the first hub segment
Data Source
AI summary
A fan assembly for a gas turbine engine includes a fan duct, a fan, and an outlet guide vane assembly located in the fan duct axially downstream of the fan. The outlet guide vane assembly includes a first variable leading edge outlet guide vane that extends radially relative to the central axis and includes a leading edge portion and a fixed aft portion, the leading edge portion including a tip segment configured to rotate about a leading edge pitch axis and a hub segment located radially inward of and separate from the tip segment, the hub segment configured to independently rotate about the leading edge pitch axis relative to the tip segment. The assembly further includes two unique gear assemblies each configured to rotate one of the tip and hub segments.