Integral ACM Rotor Shaft Assembly for Precise Bearing Alignment
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Solution Overview
Problem
Conventional air cycle machines (ACMs) in environmental control systems suffer from misalignment of journal bearing portions due to compound tolerances, leading to undesirable shaft loads, vibration, and imbalance, and require complex and heavy components for assembly.
Innovation Solution
An integral ACM rotor assembly with two turbines and a compressor mounted on a single shaft, where shaft sections are welded and machined in a single setup to provide highly aligned bearing surfaces, secured by three stops and three threaded fasteners, eliminating the need for tie rods and reducing assembly complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If multiple shaft pieces are assembled using separate machining operations, then manufacturing flexibility is improved, but manufacturing precision deteriorates due to compound tolerances
Solution Approach 1:
The shaft is divided into multiple sections that are welded together to form an integral structure. This allows the shaft to be manufactured in segments and then joined, maintaining the benefits of segmented manufacturing while achieving the alignment precision of a single-piece shaft through the welding process and subsequent single-setup machining of bearing surfaces.
Solution Approach 2:
Multiple shaft sections are merged into an integral welded structure, combining the manufacturing flexibility of multiple pieces with the alignment precision of a single piece. The welded sections are then machined together in a single setup to ensure precise bearing surfaces without compound tolerances.
2Stability of the object's composition
If complex assembly components such as tie rods are used to hold shaft pieces together, then structural stability is improved, but device complexity increases
Solution Approach 1:
The shaft sections are merged into an integral welded structure, eliminating the need for separate holding components like tie rods. This reduces device complexity while maintaining structural stability through the welded joint and simplified fastening system with stops and threaded fasteners.
Solution Approach 2:
Complex assembly components such as tie rods are extracted from the design, removing unnecessary elements that added complexity. The essential function of holding shaft pieces together is achieved through simpler means: welding the sections together and using stops with threaded fasteners for final assembly.
3Ease of manufacture
If multiple shaft pieces are assembled with separate machining, then ease of manufacturing individual components is improved, but reliability deteriorates due to misalignment and vibration
Solution Approach 1:
The shaft is segmented into weldable sections that can be manufactured separately, then joined and machined in a single setup. This maintains the ease of manufacturing individual components while ensuring reliable alignment and operation by eliminating compound tolerances and misalignment issues.
Solution Approach 2:
Multiple shaft sections are merged into an integral structure through welding, combining the manufacturing advantages of separate components with the operational reliability of a unified structure. The single-setup machining of bearing surfaces ensures proper alignment, eliminating vibration and improving 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 minimizes rotational loads, improves alignment, reduces assembly time, and enhances the performance and reliability of the ACM by eliminating unnecessary weight and complexity, resulting in more efficient energy use and reduced vibration.
Implementation Method 1
The shaft includes shaft sections that are welded together and machined in a single set-up process into a desired shaft shape
Data Source
AI summary
An air cycle machine includes two turbines and a compressor mounted on an integral shaft. The integral shaft includes a plurality of shaft sections that are welded together and machined in a single set-up process into a desired shaft shape to provide highly aligned bearing surfaces. The shaft includes three stops that cooperate with three fasteners to secure the two turbines and the compressor on the shaft.