Turbofan Engine Bearing Support for Load Management
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Solution Overview
Problem
Turbofan engines face challenges in flexing while accommodating tension loads and torsional stresses during flight, requiring innovative solutions for bearing support and transmission systems to enhance engine performance and durability.
Innovation Solution
A bearing support system with a duplex tapered roller bearing assembly and a bellows spring, coupled with a reduction transmission, is used to support the fan shaft, allowing for efficient load distribution and rotation while maintaining alignment and reducing deflection-induced fatigue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a rigid bearing support structure is used to maintain alignment, then alignment precision is improved, but engine flexibility and ability to accommodate thermal expansion deteriorates
Solution Approach 1:
The patent employs flexible bearing support structures that can deform elastically to accommodate thermal expansion and engine flexing while maintaining proper bearing alignment. These flexible structures allow the engine to adapt to thermal and mechanical loads without compromising alignment precision.
Solution Approach 2:
The bearing support structure is designed with dynamic characteristics that allow it to adapt its stiffness and alignment properties in response to operating conditions. The structure can flex under thermal load while maintaining alignment precision during operation, resolving the contradiction between rigidity and flexibility.
2Reliability
If the bearing support extends far into the compressor hub, then bearing alignment and support stability are improved, but compressor hub structural integrity and airflow path deteriorates
Solution Approach 1:
The bearing support structure is designed to extend in a tapered manner primarily in the radial dimension while minimizing axial intrusion into the compressor hub. This dimensional optimization allows the support to achieve necessary stability without excessively obstructing the airflow path through the compressor.
Solution Approach 2:
The bearing support structure features varying cross-sectional properties along its length, with the main portion having optimized taper angles (10-45° off-axial) that provide structural stability where needed while minimizing intrusion into the airflow path in critical regions.
3Force
If a duplex bearing assembly with large bearing distance is used to handle high loads, then load capacity is improved, but bearing assembly length and engine compactness deteriorates
Solution Approach 1:
The bearing support structure is designed with built-in preload mechanisms that apply preliminary axial and radial forces to the duplex bearing assembly. This preliminary action allows the bearings to operate at optimal load distribution, effectively increasing load capacity without requiring excessive bearing distance or assembly length.
Solution Approach 2:
The patent optimizes the bearing distance to diameter ratio (0.4:1 to 3:1) and uses tapered roller bearing geometry to achieve high load capacity in a compact configuration. The parameter optimization allows the bearing assembly to handle high loads while maintaining engine compactness.
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 solution effectively manages torsional and radial loads, improves engine efficiency, reduces noise, and extends the durability of the transmission system by maintaining proper alignment and reducing high cycle fatigue, thus enhancing overall engine performance.
Implementation Method 1
A bearing assembly couples the shaft to the front frame. A bearing support extends aftward and radially inward from the front frame assembly to the bearing assembly.
Implementation Method 2
A bearing assembly couples the shaft to the front frame. A bearing support extends aftward and radially inward from the front frame assembly to the bearing assembly.
Data Source
AI summary
A turbofan engine comprises an engine case. A gaspath extends through the engine case. A fan has a circumferential array of fan blades. A fan case encircles the fan blades radially outboard of the engine case. A plurality of fan case vanes extend outward from the engine case to the fan case. A front frame assembly includes a plurality of vanes extending radially across the gaspath. A transmission couples a shaft to a fan shaft to drive the fan. A bearing assembly couples the shaft to the front frame assembly. A bearing support extends aftward and radially inward from the front frame assembly to the bearing assembly.