Integral Piston Bearing Preload for Gas Turbine Standby Operation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Operating a gas turbine engine in a low-power standby mode poses challenges due to the lack of axial loading, which can lead to reduced bearing structural integrity and service life, as most engines are designed to run optimally at higher power outputs.
Innovation Solution
A tandem bearing assembly with an auxiliary bearing and a hydraulic device that applies a constant axial preload to maintain bearing stability and prevent load reversals, even in low-power conditions, ensuring the bearing remains preloaded and operational.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the engine operates in low-power standby mode to reduce fuel consumption, then fuel efficiency is improved, but bearing structural integrity deteriorates due to lack of axial loading
Solution Approach 1:
The hydraulic device applies a preliminary axial preload force to the bearing in advance, counteracting the harmful effect of load reversal and bearing separation that would occur during low-power standby operation. This preliminary action prevents the bearing from losing structural integrity before the problem can manifest.
Solution Approach 2:
The hydraulic device acts as an intermediary mechanism between the engine shaft and bearing, providing the necessary axial loading force independently of the engine's aerodynamic output. This mediator ensures the bearing remains properly loaded even when the engine operates at very low power levels.
2Loss of energy
If the engine operates in low-power standby mode, then fuel consumption is reduced, but bearing service life is reduced due to load reversal and separation
Solution Approach 1:
The hydraulic preload prevents load reversal and bearing separation by maintaining continuous axial contact between bearing components. This preliminary protective action eliminates the damaging cyclic loading that would otherwise reduce bearing service life during standby operation.
Solution Approach 2:
The hydraulic device provides beforehand cushioning by maintaining a constant axial preload force that cushions against the harmful effects of load reversal. This prior protection ensures the bearing operates under controlled loading conditions, extending its service life during low-power operation.
3Strength
If a hydraulic device is added to apply axial preload, then bearing integrity is maintained, but device complexity increases
Solution Approach 1:
The hydraulic device is merged with the bearing assembly, with the piston integrated into the bearing structure. The piston rod connects directly to the inner race, combining the hydraulic loading mechanism with the bearing components themselves, thereby reducing overall system complexity.
Solution Approach 2:
The hydraulic device serves multiple functions: it applies axial preload to maintain bearing integrity, prevents load reversal, and compensates for insufficient aerodynamic loading during standby operation. This multi-functionality reduces the need for separate systems, simplifying the overall design.
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 maintains bearing integrity and service life by providing a consistent axial load, compensating for the lack of aerodynamic load during standby mode and simplifying the hydraulic system, while also being applicable in both low-power and full-power engine operations.
Implementation Method 1
a hydraulic device that applies a constant axial preload to maintain bearing stability
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A method of operating a gas turbine engine (3) of a multi-engine aircraft (1) is disclosed, where the gas turbine engine (3) has an engine shaft (17) mounted for rotation in a bearing (20, 30) of a bearing assembly (18). The method comprises limiting motive power supplied to the aircraft (1) by the gas turbine engine (3) by operating the gas turbine engine (3) in a standby mode; and when the gas turbine engine (3) is operating in the standby mode, using an oil piston integrated in the bearing (20, 30) supporting the engine shaft (17) of the gas turbine engine (3) to generate an axial preload force on the bearing (20, 30).