Journal Bearing Subsurface Layer for Clearance Under Thermal Overload
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Solution Overview
Problem
Journal bearings in geared turbofan engines are prone to seizure due to oil interruption, gross overload, or excessive misalignment, leading to complete loss of engine power and locked fan, which existing technologies fail to adequately prevent.
Innovation Solution
A journal bearing design featuring a subsurface layer with a tailored low coefficient of thermal expansion, typically made of fibre-reinforced plastic, is introduced between the bearing body and the functional surface, reducing thermal expansion and heat transfer, thereby preventing seizure by maintaining clearance and insulating the body from high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional journal bearing body is used with high thermal conductivity material, then heat can be transmitted away effectively, but thermal expansion at high temperatures reduces clearance and causes seizure
Solution Approach 1:
The journal bearing component is segmented into distinct layers: a body made of high thermal conductivity material (e.g., steel) and a subsurface layer made of low thermal expansion material (e.g., ceramic coating or metal matrix composite). This segmentation allows each layer to perform its specialized function - the body handles heat transmission while the subsurface layer prevents thermal expansion-induced seizure.
Solution Approach 2:
The journal bearing employs composite material construction, combining materials with different thermal properties. The body uses high thermal conductivity material for heat dissipation, while the subsurface layer uses low thermal expansion material (such as ceramic coatings, cermets, or metal matrix composites) to maintain clearance at elevated temperatures, creating a composite structure that resolves the contradiction between heat transmission and thermal expansion.
2Stability of the object's composition
If the coefficient of thermal expansion of the bearing material is high, then the material can accommodate thermal stress, but thermal expansion reduces clearance and leads to seizure
Solution Approach 1:
Different regions of the journal bearing are assigned different material qualities tailored to their specific functional requirements. The subsurface layer in contact with the bearing partner uses low thermal expansion material to maintain clearance, while the body material provides structural support and heat conduction. This local differentiation of material properties resolves the contradiction between thermal stress accommodation and clearance maintenance.
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 journal bearing effectively reduces the risk of seizure by minimizing thermal expansion and heat transfer, ensuring continued operation even under conditions that would typically lead to seizure in conventional designs.
Implementation Method 1
The first subsurface layer is formed of a material having a first coefficient of thermal expansion in the radial direction, and the first body is formed of a material having a second coefficient of thermal expansion in the radial direction. It is provided that the first coefficient of thermal expansion is lower than the second coefficient of thermal expansion.
Implementation Method 2
reducing thermal expansion and heat transfer, thereby preventing seizure by maintaining clearance and insulating the body from high temperatures
Data Source
AI summary
A journal bearing comprising a first component and a second component, the first and second components being arranged to rotate relative to one another in normal use. The first component comprises a first body, a first layer forming a functional surface facing the second component, and a first subsurface layer between the body and the layer. The first subsurface layer is formed of a material having a first coefficient of thermal expansion in the radial direction, and the first body is formed of a material having a second coefficient of thermal expansion in the radial direction. The first coefficient of thermal expansion is lower than the second coefficient of thermal expansion.