Fan Case Stiffness Ratio via A-Frame and Guide Vanes
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Solution Overview
Problem
Modern gas turbine engines with gear reduction systems face challenges in achieving optimal structural support and stiffness between the fan case and core housing, particularly with longer low pressure compressors, which require improved mounting arrangements to manage torque and operational loads effectively.
Innovation Solution
The integration of A-frame connections and a reduced number of structural fan exit guide vanes, with specific stiffness ratios and gap configurations, provides enhanced moment and lateral stiffness, allowing for efficient load distribution and operational stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If multiple structural fan exit guide vanes are used to connect fan case and core housing, then structural support and stiffness are improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The mounting arrangement is segmented into two distinct types of structural elements: fan exit guide vanes and A-frame connections. This segmentation allows each element to serve specific structural functions independently, providing flexibility in the overall design while maintaining simplicity in individual component fabrication and assembly.
Solution Approach 2:
The fan exit guide vanes serve dual functions: they provide structural support between the fan case and core housing, and they guide the airflow from the fan to the bypass duct. This multi-functionality reduces the need for separate structural and aerodynamic components, thereby simplifying the overall device complexity.
2Stability of the object's composition
If more fan exit guide vanes are used for structural support, then moment stiffness is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a moment stiffness ratio between 0.50 and 2.0, which provides a broad acceptable range for manufacturing variations. This parameter range allows for flexibility in manufacturing while ensuring adequate structural performance, reducing the stringency of precision requirements compared to tighter tolerances.
Solution Approach 2:
The mounting arrangement combines different structural elements (fan exit guide vanes and A-frame connections) with potentially different material properties and structural characteristics. This composite approach allows the system to achieve the required moment stiffness through the combined effect of multiple components rather than relying on a single critical component with tight tolerance requirements.
3Strength
If A-frame connections are added to provide structural support, then lateral stiffness is improved, but device complexity increases
Solution Approach 1:
The A-frame connections are merged with the existing compressor housing structure, utilizing the housing as part of the load-bearing path. This integration approach adds lateral stiffness without requiring completely separate structural components, thereby limiting the increase in device complexity.
Solution Approach 2:
The A-frame connections act as intermediary structural elements that transfer loads between the fan case and the compressor housing. By positioning these A-frames at strategic locations, they efficiently mediate the load transfer path, providing lateral stiffness support without requiring a complex network of connections throughout the entire structure.
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
A gear reduction (104) reduces a speed of a fan rotor (106) relative to a speed of a fan drive turbine. A rigid connection between a fan case (108) and an inner core housing includes a plurality of A-frames (116) connected at a connection point (122) to the fan case (108). Legs in the A-frames (116) extend away from the connection point (122) in opposed circumferential directions to be connected to a compressor wall (111) of the inner core housing. The rigid connection also includes a plurality of fan exit guide vanes (114, 129) rigidly connected to the fan case (108). A lateral stiffness ratio of the lateral stiffness of the plurality of fan exit guide vanes (114, 129) and a lateral stiffness of a combination of the plurality of A-frame, the compressor wall (111), and a fan intermediate case (210) which is forward of the low pressure compressor (44, 112) being greater than or equal to 0.6 and less than or equal to 2.0.