Dual-Bearing Assembly for Low-Thrust Shaft Vibration Control
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Solution Overview
Problem
Turbine engines experience high transient vibrations in the high pressure shaft during aircraft climb due to leakage across piston seal rings, leading to reduced rotor thrust and axial and radial stiffness, causing non-synchronous vibrations and instability.
Innovation Solution
A bearing assembly with a secondary, false bearing that provides additional axial stiffness during low thrust conditions, creating an active axial load path to mitigate vibrations and maintain rotor thrust control, avoiding non-synchronous vibrations and modal instability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a single bearing is used to support the rotating shaft, then the device complexity is low, but the axial stiffness is insufficient during low thrust conditions causing vibrations and instability
Solution Approach 1:
The bearing assembly is segmented into a primary bearing and a secondary false bearing that operate independently under different thrust conditions. The primary bearing handles high thrust conditions while the secondary false bearing provides support during low thrust and thrust reversal conditions, allowing each bearing to be optimized for its specific operating range.
Solution Approach 2:
The bearing assembly dynamically transitions between different bearing configurations based on thrust conditions. During high thrust, the primary bearing is active while the secondary bearing is inactive. During low thrust and thrust reversal, the roles reverse, providing continuous optimal support without requiring a complex active control system.
2Stability of the object's composition
If bearing stiffness is increased to reduce vibrations, then the stability improves, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The bearing assembly is segmented into a primary bearing and a secondary false bearing that operate independently under different thrust conditions. The primary bearing handles high thrust conditions while the secondary false bearing provides support during low thrust and thrust reversal conditions, allowing each bearing to be optimized for its specific operating range.
Solution Approach 2:
The system changes the effective bearing stiffness parameter dynamically by switching between different bearing configurations. During low thrust conditions, the secondary false bearing is activated to provide additional axial stiffness, while during high thrust conditions, the primary bearing provides the main support, optimizing performance across the entire operating range.
3Object-affected harmful factors
If a secondary false bearing is added to provide additional axial stiffness, then the vibration control improves, but the device complexity increases
Solution Approach 1:
The secondary false bearing acts as an intermediary element that provides additional axial stiffness during low thrust and thrust reversal conditions. It mediates the support function between the primary bearing and the rotating shaft, engaging only when needed to reduce vibrations without interfering with the primary bearing's operation during high thrust conditions.
Solution Approach 2:
The system changes the effective bearing stiffness parameter dynamically by switching between different bearing configurations. During low thrust conditions, the secondary false bearing is activated to provide additional axial stiffness, while during high thrust conditions, the primary bearing provides the main support, optimizing performance across the entire operating range.
Data Source
AI summary
A gas turbine engine including a rotating shaft and a bearing assembly. The bearing assembly is configured to support the rotating shaft. The bearing assembly has a first bearing and a second bearing. The first bearing is configured to support an axial load of the rotating shaft when a forward thrust of the rotating shaft is greater than ten percent. The second bearing is configured to support the axial load of the rotating shaft when a thrust of the rotating shaft is between ten percent forward thrust and ten percent aft thrust, inclusive of the end points.