Segmented Fan Outlet Guide Vanes for Distorted Airflow
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Solution Overview
Problem
Fan blades in gas turbine engines experience operability issues due to variations in intake airflow and pressure fluctuations, leading to inefficiencies and performance degradation.
Innovation Solution
A fan assembly with a variable leading edge outlet guide vane assembly that includes a first tip segment and a first hub segment, both configured to rotate independently, controlled by a cam actuation mechanism, allowing for adjustable pitch angles to manage airflow direction and reduce incidence, thereby improving fan operability and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed outlet guide vane assembly is used, then the structure is simple, but it cannot accommodate distorted airflows and pressure fluctuations, leading to fan operability issues
Solution Approach 1:
The outlet guide vane assembly is divided into multiple independent segments including a tip segment and a hub segment that can rotate independently about a leading edge pitch axis. This segmentation allows each segment to be controlled separately by individual cam mechanisms, enabling the assembly to adapt to distorted airflow patterns while maintaining a manageable structural complexity through modular design
Solution Approach 2:
The outlet guide vane assembly transitions from a fixed structure to a dynamic one where the tip and hub segments can independently adjust their pitch angles. This dynamic capability allows the assembly to respond to varying airflow conditions and pressure fluctuations, improving adaptability while the use of cam mechanisms provides controlled movement without excessive complexity
2Adaptability or versatility
If the tip segment and hub segment rotate together as one unit, then the control mechanism is simpler, but it cannot independently optimize airflow at different radial positions
Solution Approach 1:
The leading edge portion is segmented into a tip segment and a hub segment that rotate independently about the same leading edge pitch axis. Each segment has its own cam actuation mechanism, allowing independent control of pitch angles at different radial positions. This segmentation enables optimized airflow control while the modular cam mechanisms keep the overall system complexity manageable
Solution Approach 2:
Different segments of the outlet guide vane are given different degrees of freedom through independent rotation capabilities. The tip segment and hub segment can be positioned at different pitch angles to locally optimize airflow at their respective radial positions, with each segment's cam mechanism providing targeted control without requiring complex coordinated actuation
3Adaptability or versatility
If a single cam mechanism controls both tip and hub segments, then the actuation system is simpler, but it cannot provide unique pitch angles for each segment
Solution Approach 1:
The cam actuation system is segmented into multiple independent cam mechanisms mounted on a common cam rod. Each cam (first cam for tip segment, second cam for hub segment) can be independently positioned along the cam rod, allowing each segment to achieve unique pitch angles. This segmentation provides independent control capability while the shared cam rod structure maintains reasonable system complexity
4Productivity
If the outlet guide vane assembly is made stationary, then manufacturing is easier, but it cannot improve fan operability under varying airflow conditions
Solution Approach 1:
The outlet guide vane assembly is designed with dynamic segments that can rotate about a leading edge pitch axis, allowing the tip and hub segments to adjust their pitch angles in response to varying airflow conditions. This dynamic capability improves fan efficiency and operability while the use of established cam mechanisms and modular segmentation keeps manufacturing complexity manageable
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 a single actuation assembly includes a cam rod and cams arranged thereon that is configured to rotate the tip and hub segments via the cams.