Variable-Pitch Outlet Guide Vanes for Fan Stall Mitigation
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Solution Overview
Problem
Gas turbine engine fan assemblies face operability issues due to variations in intake airflow and pressure fluctuations, leading to inefficiencies and potential damage from forces like forcing, stall, and flutter, which existing technologies fail to adequately address.
Innovation Solution
A fan assembly with a variable-pitch outlet guide vane system, including multiple vanes that can rotate to adjust airflow direction based on operating conditions, is integrated with a control system to optimize airflow and reduce losses caused by distortions and disturbances, using actuators and mechanical connections to adjust vane angles dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed-pitch outlet guide vanes are used, then the structure is simple, but the fan blades experience forcing, stall, and flutter due to variations in intake airflow and pressure fluctuations
Solution Approach 1:
The patent applies the dynamics principle by transitioning from fixed-pitch to variable-pitch outlet guide vanes. Each vane can rotate about its pitch axis to adjust its pitch angle dynamically in response to varying operating conditions, allowing the system to adapt to intake airflow variations and pressure fluctuations, thereby preventing forcing, stall, and flutter on fan blades.
Solution Approach 2:
The patent implements parameter changes by varying the pitch angle of the outlet guide vanes based on operating conditions. The control system adjusts the pitch parameter of each vane to optimize airflow direction and reduce adverse effects on fan blade performance, transforming a static system into one that continuously adapts its geometric parameters.
2Ease of operation
If variable-pitch outlet guide vanes are implemented, then fan blade operability is improved, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the outlet guide vane assembly into multiple independently controllable vanes, each with its own pitch control capability. This segmentation allows selective adjustment of individual vanes or groups of vanes to address specific airflow distortion patterns, providing precise control while managing system complexity through modular architecture.
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 system effectively reduces operational issues such as forcing, stall, and flutter by optimizing airflow direction and incidence, improving engine performance and efficiency by minimizing losses and maintaining uniform airflow.
Implementation Method 1
the first variable-pitch outlet guide vane being configured to rotate about a first pitch axis to a first vane-pitch angle in response to the gas turbine engine operating at a given operating condition so as to redirect the fan exit air in a first direction
Data Source
AI summary
A fan assembly includes a fan duct, an inlet fan, and an outlet guide vane assembly. The inlet fan includes blades adapted to force fan exit air toward an aft end of the fan duct. The outlet guide vane assembly is located in the fan duct downstream of the inlet fan and is configured to adjust a direction of the fan exit air received from the blades. The outlet guide vane assembly includes a first plurality of outlet guide vanes including a first outlet guide vane configured to rotate to a first angle so as to redirect the fan exit air in a first direction and a second outlet guide vane configured to rotate to a second angle so as to redirect the fan exit air in a second direction. The second outlet guide vane is located at a different circumferential position than the first outlet guide vane.