Thrust Foil Bearing Leaf Geometry for Load Capacity
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Solution Overview
Problem
Thrust foil bearings face challenges in securing a predetermined load capacity due to the management of radial bearing clearance and thermal expansion in high-temperature, high-speed environments, particularly in turbomachines like gas turbines.
Innovation Solution
The thrust foil bearing is designed with a specific arrangement of leaves where the ratio of the circumferential length of the top foil portion to the radial length is set between 0.66 and 0.55, allowing for a controlled number of leaves to be arranged, thereby securing a certain load capacity while minimizing manufacturing costs and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the number of leaves is increased to secure load capacity, then the load capacity is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent applies parameter changes by optimizing the aspect ratio of each leaf to a specific range (0.55-0.66) to achieve maximum load capacity efficiency. This allows fewer leaves to be used while maintaining the required load capacity, thereby reducing device complexity and manufacturing cost without compromising strength
2Stability of the object's composition
If the radial bearing clearance is strictly managed to ensure stability, then the stability is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies dynamics by making the bearing surface flexible through the leaf structure, allowing it to adapt to thermal expansion and clearance variations dynamically. This eliminates the need for strict clearance management during manufacturing while maintaining bearing stability under varying operating conditions
Solution Approach 2:
The patent accounts for thermal expansion by designing the flexible leaf structure that can accommodate clearance changes due to temperature variations. This allows the bearing to maintain stability across a wide temperature range without requiring precise clearance control during manufacturing
3Device complexity
If the leaf aspect ratio is decreased to reduce the number of leaves, then the device complexity is reduced, but the load capacity may be compromised
Solution Approach 1:
The patent identifies and applies parameter changes by determining the optimal aspect ratio range (0.55-0.66) for each leaf. Within this range, each leaf achieves maximum load-bearing efficiency, allowing the bearing to use fewer leaves while maintaining sufficient load capacity. This optimizes the balance between device complexity and strength
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 ensures a secure load capacity while reducing the number of leaves, lowering manufacturing costs and enhancing product reliability, with the optimal ratio of 0.6 providing the minimum necessary load capacity without significant cost or performance variation.
Implementation Method 1
when the shaft rotates, an air film is formed between an outer peripheral surface of the shaft and an inner peripheral surface of the top foil, and the shaft is supported in a non-contact manner
Implementation Method 2
a spring-like member called a back foil is disposed on an outer diameter side of the thin plate to elastically support a load applied to the top foil by the back foil
Data Source
AI summary
A thrust foil bearing 40 having a thrust bearing surface S formed by arranging a plurality of leaves 42 side by side in a circumferential direction, in which each of the leaves 42 has a top foil portion Tf that forms the thrust bearing surface S, and a ratio of a circumferential length A of the top foil portion Tf of one of the leaves 42 at a radially central position of the top foil portion Tf, to a radial length B from an inner diameter-side edge 423 to an outer diameter-side edge 424 of the top foil portion Tf is 0.66 or less.