Inter-shaft bearing reduces vibration in coaxial gas turbine shafts
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Solution Overview
Problem
Long gas turbine engine shafts are susceptible to bending during operation, necessitating improved support mechanisms to prevent structural issues.
Innovation Solution
The implementation of an inter-shaft bearing mounted in an annular space between the high pressure (HP) and low pressure (LP) shafts, which are coaxially arranged, provides axial support and reduces vibration transfer through a flexible coupling, allowing independent rotation of the LP and HP spools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If long shafts are used in gas turbine engines, then the engine can achieve higher power output and larger compressor/turbine stages, but the shafts become susceptible to bending and structural instability during operation
Solution Approach 1:
The patent divides the long shaft system into multiple supported sections by introducing an inter-shaft bearing that contacts both the HP shaft and LP shaft. This segmentation provides intermediate support points, effectively reducing the unsupported span length of each shaft and preventing bending while maintaining the overall long shaft configuration needed for high power output.
Solution Approach 2:
The inter-shaft bearing acts as an intermediary element between the HP shaft and LP shaft. This bearing provides structural support to both shafts simultaneously, transferring loads and preventing bending without requiring the shafts to be directly connected or rigidly coupled, thus maintaining operational reliability.
2Power
If the HP shaft and LP shaft are rigidly coupled, then torque transfer efficiency is improved, but vibration between the two independently rotating spools is amplified and transferred
Solution Approach 1:
The patent employs a flexible coupling mechanism through the inter-shaft bearing arrangement that allows relative motion and vibration isolation between the HP and LP shafts. The bearing configuration provides a compliant connection that accommodates differential vibrations while maintaining sufficient torque transfer capability, effectively decoupling harmful vibrations from the rigid torque transmission path.
3Device complexity
If the LP shaft is extended axially inside the HP shaft to connect turbines and compressors, then the engine layout is optimized and space is efficiently utilized, but the LP shaft becomes longer and more prone to bending
Solution Approach 1:
By introducing the inter-shaft bearing as an intermediate support, the patent effectively segments the long LP shaft into shorter supported sections. This allows the LP shaft to maintain its extended axial configuration inside the HP shaft for optimized engine layout, while the bearing provides necessary structural support to prevent bending in the longer shaft configuration.
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
This configuration effectively supports long LP shafts, reduces vibration transfer, and maintains efficient torque transfer between the LP and HP turbines and compressors, enhancing the structural integrity and operational stability of the gas turbine engine.
Implementation Method 1
an inter-shaft bearing mounted in an annular space between the HP shaft and LP shaft
Data Source
AI summary
A multi-spool gas turbine engine comprises a low pressure (LP) spool and a high pressure (HP) spool. The LP spool has an LP shaft for transferring a torque from an LP turbine to an LP compressor. The HP spool has an HP shaft for transferring a torque from an HP turbine to an HP compressor. The LP shaft is coaxially mounted inside the HP shaft. An inter-shaft bearing is mounted radially between the LP shaft and the HP shaft. The inter-shaft bearing is disposed axially between the HP compressor and the LP compressor.