Two-Wheel Air Cycle Machine Thrust-Free Shaft Design
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Solution Overview
Problem
Conventional air cycle machines face challenges in reducing friction and balancing thrust loading during start-up, which affects the efficiency of the rotating components due to friction from thrust bearings.
Innovation Solution
A two-wheel air cycle machine design featuring a compressor end shaft with a radially-extending seal disk and axially-extending shaft portion, including apertures that define a compressor inlet flow path, helps maintain balanced thrust loads and adequate startup pressure through a balanced circumferential flow path and sealing features like knife edges and abradable seals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional thrust bearings are used to support the shaft, then the rotating components can be supported during operation, but friction from thrust loading creates resistance during start-up
Solution Approach 1:
The patent extracts the thrust bearing from the shaft support system and replaces it with a thrust-free bearing arrangement. The compressor and turbine are mounted on separate shafts that do not require thrust bearings, eliminating the friction resistance problem while maintaining reliable shaft support through journal bearings alone.
Solution Approach 2:
The patent replaces the mechanical thrust bearing system with a thrust-free mechanical arrangement using balanced circumferential flow paths and symmetric mounting configurations to eliminate axial thrust forces, thereby eliminating friction resistance during start-up while maintaining operational reliability.
2Force
If a diaphragm valve is added to balance thrust loading, then thrust loading can be balanced, but device complexity increases
Solution Approach 1:
The patent removes the diaphragm valve from the system entirely by adopting a thrust-free bearing arrangement. The thrust balance is achieved through symmetric mounting of compressors and turbines on separate shafts, eliminating the need for additional balancing components and reducing device complexity.
Solution Approach 2:
The patent replaces the diaphragm valve-based thrust balancing system with a simpler thrust-free mechanical arrangement using balanced circumferential flow paths and symmetric configurations, achieving thrust balance without additional complex components.
3Reliability
If conventional bearing arrangements are used, then shaft rotation can be supported, but friction affects efficiency during start-up
Solution Approach 1:
The patent extracts the thrust bearing from the shaft rotation support system and replaces it with a thrust-free bearing arrangement using symmetric mounting and balanced flow paths, eliminating friction resistance during start-up while maintaining reliable shaft rotation support through journal bearings.
Solution Approach 2:
The patent replaces the conventional bearing arrangement with a thrust-free mechanical system using balanced circumferential flow paths and symmetric compressor-turbine mounting, eliminating friction effects during start-up while maintaining shaft rotation support efficiency.
Data Source
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AI summary
A two-wheel air cycle machine includes a tie rod (18) defining an axis, a turbine (14) mounted on the tie rod, and a compressor (16) mounted on the tie rod and having a rotor portion (32) and a disk portion (32D) with at least one aperture (54). The air cycle machine further includes a compressor inlet (26) fluidly connecting the compressor and an inlet air source, at least one thrust bearing (50) disposed between the turbine and the compressor, and a compressor end shaft (38) coaxial with the tie rod and abutting the compressor disk portion. The compressor end shaft includes a radially-extending seal disk portion (60) and an axially-extending shaft portion (58) having at least one shaft aperture (62). The at least one disk aperture and the at least one shaft aperture are fluidly connected by a compressor disk cavity (56) defined by a gap between the tie rod and the compressor disk portion. The at least one disk aperture, the compressor disk cavity, and the at least one shaft aperture at least partially define a compressor inlet flow path.