Turbine Engine High-Speed Shaft Rating for Stable Bypass Operation
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Solution Overview
Problem
Turbine engines with higher bypass ratios face instability due to reduced stiffness-to-weight ratio and increased excitation of bending modes, leading to excessive vibrations and reduced efficiency.
Innovation Solution
Optimized shaft geometries and materials, such as ceramic matrix composites, combined with additive manufacturing, to enhance shaft stability and reduce vibrations, allowing for higher redline speeds and improved engine performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If higher bypass ratios are used to improve engine efficiency, then fuel efficiency improves, but shaft stability deteriorates due to reduced stiffness-to-weight ratio and increased bending mode excitation
Solution Approach 1:
The patent applies composite materials, specifically ceramic matrix composites (CMCs), to shaft components to achieve higher stiffness-to-weight ratios. This allows the shaft to maintain stability at higher bypass ratios while reducing overall weight, thereby resolving the contradiction between fuel efficiency and shaft stability.
Solution Approach 2:
The patent changes material parameters by transitioning from traditional metals to ceramic matrix composites, fundamentally altering the stiffness-to-weight ratio. This parameter change enables the shaft to withstand higher bypass ratios without excessive vibrations, simultaneously improving fuel efficiency and maintaining stability.
2Ease of manufacture
If traditional materials and geometries are used, then manufacturing simplicity is maintained, but shaft vibrations increase at higher bypass ratios
Solution Approach 1:
The patent applies local quality by using additive manufacturing to create non-uniform shaft geometries with varying cross-sectional properties along the shaft length. This allows optimization of stiffness distribution to reduce vibrations at specific locations while maintaining manufacturing feasibility through additive processes.
Solution Approach 2:
The patent introduces dimensional complexity by moving from traditional uniform cylindrical geometries to three-dimensionally optimized shaft structures. Additive manufacturing enables complex spatial configurations that improve vibration characteristics while remaining manufacturable through advanced additive processes.
3Stability of the object's composition
If shaft stiffness is increased to reduce vibrations, then shaft stability improves, but engine core length increases
Solution Approach 1:
The patent uses ceramic matrix composites to achieve higher stiffness-to-weight ratios, allowing increased shaft stiffness without proportionally increasing length. The superior material properties enable compact shaft designs that maintain stability while minimizing engine core length.
Solution Approach 2:
The patent optimizes shaft dynamics by carefully tuning the stiffness distribution and natural frequencies of the shaft system. This dynamic optimization allows the shaft to achieve adequate stability with minimized length by avoiding resonance conditions and optimizing modal characteristics.
Data Source
AI summary
A turbomachine engine includes an engine core including a high-pressure compressor, a high-pressure turbine, and a combustion chamber in flow communication with the high-pressure compressor and the high-pressure turbine. The engine core has a length (LCORE), and the high-pressure compressor has an exit stage diameter (DCORE). A high-pressure shaft is coupled to the high-pressure compressor and the high-pressure turbine. The high-pressure shaft is characterized by a high-speed shaft rating (HSR) from 1.5 to 6.2, and a ratio of LCORE/DCORE is from 2.1 to 4.3.