Geared Gas Turbine Rigid Connection Stiffness
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Solution Overview
Problem
The incorporation of a gear reduction between the fan drive turbine and the fan rotor in gas turbine engines poses mounting challenges due to increased torque and load requirements, particularly with longer low pressure compressors that demand higher structural stiffness to manage these loads effectively.
Innovation Solution
The implementation of a rigid structure comprising A-frames and fan exit guide vanes, which provide enhanced moment stiffness and load paths between the fan case and the inner core engine, along with a gear reduction mechanism to adjust the fan rotor speed relative to the fan drive turbine, ensuring adequate structural support and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a gear reduction is incorporated between the fan drive turbine and the fan rotor, then the fan rotor speed is reduced relative to the fan drive turbine speed, but mounting challenges arise due to increased torque and load requirements
Solution Approach 1:
The rigid connection is divided into multiple discrete components: A-frames with legs, fan exit guide vanes, and a rigid structure. Each component serves as a separate load path, distributing the mounting challenges across multiple elements rather than requiring a single complex connection solution.
Solution Approach 2:
Multiple structural elements (A-frames, fan exit guide vanes, and rigid structure) are combined to work together as an integrated rigid connection system. This merging of components creates multiple load paths that collectively manage the increased torque and loads from the gear reduction.
2Productivity
If longer low pressure compressors are used, then compressor performance is improved, but structural stiffness requirements increase to manage torque and loads
Solution Approach 1:
The rigid connection extends in multiple spatial dimensions with A-frames having legs positioned at different locations, fan exit guide vanes arranged circumferentially, and a rigid structure providing additional dimensional support. This multi-dimensional arrangement creates redundant load paths that manage torque and loads effectively.
Solution Approach 2:
The rigid connection employs a composite structural system combining different elements (A-frames, guide vanes, rigid structure) that work together to achieve the required structural stiffness. Each component contributes different structural properties, creating a composite connection system.
3Reliability
If multiple load paths are created between the fan case and inner core engine, then torque and loads are managed effectively, but device complexity increases
Solution Approach 1:
The A-frames serve multiple functions: they provide structural support, create load paths, and connect the fan case to the inner core engine. The fan exit guide vanes also serve dual purposes as both aerodynamic components and structural load-bearing elements in the rigid connection.
Data Source
AI summary
A gas turbine engine includes a fan rotor driven by a fan drive turbine about an axis through a gear reduction. An inner core engine has an inner core engine housing surrounding a compressor section, including a low pressure compressor. A rigid connection between a fan case and the inner core engine includes A-frames rigidly connected at a connection point to the fan case. Fan exit guide vanes rigidly connect to the fan case, and to the inner core engine. A fan intermediate case is positioned forward of a first rotor stage in the low pressure compressor. A rigid structure is connected to the inner core engine and to the fan exit guide vanes. The rigid structure defines a structure moment stiffness. The fan intermediate case defines an intermediate case moment stiffness. A ratio of the structure moment stiffness to the intermediate case moment stiffness is between 5 and 15.