Gas Turbine Fan Shaft Thrust Balance via Biasing Device
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Solution Overview
Problem
In gas turbine engines with a gear train, the separation of axial loads between the fan and turbine sections due to the gear train's support of torsional loads, rather than axial loads, leads to increased bearing loads and reduced bearing life, as the fan section no longer counteracts the aft-directed forces from the turbine section.
Innovation Solution
A biasing device with an actuator, such as a hydraulic or electromagnetic press, is used to apply a compressive force to the shaft, allowing the actuator to remain stationary while counteracting the axial loads, thereby reducing the load on the bearing assemblies during periods of elevated or maximum load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a gear train is introduced between the fan section and turbine section to enable high-speed rotation, then the rotational speed of the fan section is improved, but the bearing load increases and bearing life decreases
Solution Approach 1:
A thrust bearing assembly is introduced as an intermediary component between the turbine section and bearing assemblies to mediate the axial loads. The thrust bearing assembly captures and supports the axial forces from the turbine section, preventing these loads from being transmitted to the bearing assemblies that support the shaft, thereby protecting them from excessive wear and failure
Solution Approach 2:
The thrust bearing assembly acts as a counterbalancing mechanism that provides an opposing force to the axial loads generated by the turbine section. By positioning the thrust bearing assembly to face the axial forces, it creates a counteracting support system that neutralizes the harmful loads on other bearing assemblies
2Adaptability or versatility
If the fan section is separated from counteracting turbine forces by the gear train, then the gear train achieves torsional load support, but the axial load balance is lost and bearing size must increase
Solution Approach 1:
The thrust bearing assembly serves as a specialized intermediary component that handles axial loads separately from the gear train's torsional load management. This dedicated thrust bearing assembly allows the gear train to focus on its torsional function while the thrust bearing assembly independently manages axial forces, preventing the need for oversized bearing assemblies
3Force
If bearing assemblies support increased axial loads from the turbine section, then the axial force balance is maintained, but the bearing size increases and reliability decreases
Solution Approach 1:
The bearing support system is segmented into specialized components: the thrust bearing assembly specifically handles axial loads from the turbine section, while other bearing assemblies support radial loads and shaft rotation. This functional segmentation allows each bearing type to be optimized for its specific load type, preventing any single bearing assembly from being overloaded and maintaining overall system reliability
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 solution effectively balances the axial loads, reducing the stress on bearing assemblies and extending their lifespan by counteracting the aft-directed forces from the turbine section during high-load conditions, while disabling the biasing device during normal operations to avoid unnecessary stress.
Implementation Method 1
the biasing device includes a hydraulic press in communication with the shaft. The fluid conduit includes a valve configured to selectively control the amount of hydraulic fluid entering the hydraulic press
Implementation Method 2
the biasing device includes an electromagnetic press
Data Source
Figure 1
Figure 2~3
AI summary
A gas turbine engine according to an exemplary aspect of the present disclosure includes, among other things, a fan section, a shaft including a bearing system, a turbine section in communication with the shaft, a speed change mechanism coupling the fan section to the turbine section and a biasing device configured to apply a biasing force against the shaft.