Cantilevered Compressor Shaft With Flexible Coupling
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Solution Overview
Problem
Motor-driven compressors with multiple compression sections face limitations in wheel selection, maintenance complexity, and operational range due to high rotational speeds and the use of expensive active magnetic bearings, which are sized for transient states and nominal operations, restricting the variation of compression ratio and speed.
Innovation Solution
A motor-driven compressor design featuring at least two transmission shafts with flexible coupling devices, cantilevered and bearing-mounted compression sections, and axial thrust abutments to manage thrust forces, allowing for independent dynamic balancing and increased critical speed, thereby reducing bearing magnetic capacity and facilitating maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high rotational speeds are used to increase productivity, then the compressor can achieve higher output, but the shaft passes through the first bending mode causing deformation and requiring expensive large-capacity active magnetic bearings
Solution Approach 1:
The compressor is divided into two independent shaft systems: a first shaft carrying the motor and a second shaft carrying the compression sections. This segmentation allows each shaft to be optimized independently, with the second shaft designed as a cantilevered structure to increase its critical speed above the operating range, eliminating shaft deformation issues while maintaining high productivity.
Solution Approach 2:
A flexible coupling device is introduced as an intermediary between the first shaft (motor) and the second shaft (compression sections). This coupling transmits rotational motion while allowing independent dynamic behavior of each shaft, enabling the second shaft to operate below its critical speed without experiencing resonance or deformation.
2Reliability
If active magnetic bearings are sized for transient states to prevent shaft deformation, then shaft reliability is improved, but the bearing cost and electronic control device cost increase significantly
Solution Approach 1:
By segmenting the shaft system into two independent shafts, the dynamic loads on bearings are reduced. The cantilevered second shaft is designed to operate below its critical speed, allowing the use of smaller, less expensive active magnetic bearings that are sized for nominal operation rather than transient states.
3Device complexity
If compression sections are mounted on a single shaft with the motor, then the structure is compact, but maintenance requires dismantling connected pipes and the operational range is limited
Solution Approach 1:
The compression sections are separated onto an independent second shaft that can be accessed separately from the motor shaft. This allows maintenance personnel to service the compression wheels and related components without dismantling pipe connections, significantly reducing maintenance complexity while maintaining a compact overall structure.
Solution Approach 2:
The flexible coupling between the two shafts allows independent rotation and maintenance of each shaft system. The second shaft can be stationary or rotated at different speeds independent of the motor shaft, enabling dynamic maintenance operations without affecting the motor or pipe connections.
4Device complexity
If a single compression wheel per section is used to simplify the structure, then the device complexity is reduced, but the wheel selection is limited and the compression ratio variation range is restricted
Solution Approach 1:
By placing compression sections on an independent second shaft, the system allows for multiple compression wheels to be mounted on this shaft without increasing motor shaft complexity. This segmentation enables versatile wheel selection and compression ratio adjustment while maintaining simple individual section structures.
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 design enhances the operational range of the compressor, reduces the cost of active magnetic bearings, and simplifies maintenance by allowing operation below the critical speed of the first bending mode, improving wheel selection and efficiency while minimizing stress on bearings.
Implementation Method 1
a flexible coupling device connecting the drive shafts
Implementation Method 2
the at least two transmission shafts being supported in rotation in the housing by at least two bearings
Implementation Method 3
an active magnetic bearing is arranged between a compression section and the electric motor
Implementation Method 4
The compression sections are cantilevered to increase the value of the critical speed of the compression shaft
Implementation Method 5
axial thrust abutments to manage thrust forces
Data Source
AI summary
A motor-driven compressor equipped with multiple compression sections, the motor-driven compressor including, at least one housing, at least two drive shafts, the at least two drive shafts being rotatably supported in the housing by at least two bearings, a flexible coupling device connecting the drive shafts, an electric motor mounted on a first compression shaft of the at least two drive shafts, and at least two compression sections. A first compression section of the at least two compression sections is cantilevered at a free end of a first compression shaft of the at least two drive shafts, and a second compression section is mounted between two bearings on a second compression shaft of the at least two drive shafts.