Geared Fan Exit Guide Vane Stagger Angle Optimization
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Solution Overview
Problem
Gas turbine engines face challenges in achieving optimal thermal, transfer, and propulsive efficiencies, particularly in the design of fan sections and exit guide vanes, which affect the overall performance and compactness of the engine.
Innovation Solution
The design incorporates a turbine-driven fan rotor with a duct and a fan exit guide vane assembly featuring exit guide vanes with stagger angles less than 15° at the midspan portion, a geared architecture, and a bypass ratio greater than 6.0, optimizing the fan pressure ratio and reducing shock losses through a specific geometry and arrangement of guide vanes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the fan pressure ratio is increased to improve propulsive efficiency, then the engine performance improves, but the engine size and complexity increase
Solution Approach 1:
The patent applies parameter changes by optimizing the stagger angle of exit guide vanes to less than 15 degrees and configuring the fan pressure ratio to be less than 1.5. These specific parameter adjustments improve propulsive efficiency while maintaining a manageable engine pressure ratio, thereby enhancing performance without proportionally increasing engine complexity
2Loss of energy
If the stagger angle of exit guide vanes is reduced to reduce shock losses, then energy loss decreases, but the airflow control capability may be compromised
Solution Approach 1:
The patent applies parameter changes by setting the stagger angle of exit guide vanes to less than 15 degrees, with specific embodiments indicating angles between 5-15 degrees. This optimized angle range reduces shock losses in the bypass flow while maintaining adequate airflow control capability, resolving the contradiction between energy loss reduction and airflow control reliability
3Volume of moving object
If the fan pressure ratio is kept low to reduce engine size, then the engine becomes more compact, but the propulsive efficiency may decrease
Solution Approach 1:
The patent applies parameter changes by optimizing the fan pressure ratio to be less than 1.5 and configuring the exit guide vane stagger angle to less than 15 degrees. This combination of parameters achieves a compact engine design while maintaining high propulsive efficiency through reduced shock losses and optimized bypass flow management, effectively resolving the contradiction between engine compactness and propulsive efficiency
Data Source
AI summary
A fan exit guide vane assembly for a gas turbine engine includes a plurality of guide vanes having a pressure side and a suction side extending between a leading edge and a trailing edge. The vanes further include a span extending between a root and tip with a stagger angle defined as an angle between a longitudinal axis parallel to an engine axis of rotation and a line connecting the leading edge and the trailing edge that is less than about 15°.