Centrifugal Compressor Bearing Layout for Surge Load Support
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Solution Overview
Problem
Centrifugal compressors face challenges in efficiently supporting radial loads on impellers, leading to shaft bending and potential damage during surges, especially when impeller-side radial bearings are not adequately positioned relative to the cover member.
Innovation Solution
The design incorporates a cover member that covers the impeller blades radially and positions the impeller-side radial bearing outside the cover member to support radial loads, using either gas bearings for high-speed operation or static pressure gas bearings for initial load support, thereby reducing shaft bending and protecting rotor-side bearings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the impeller-side radial bearing is positioned inside the cover member, then the device complexity is reduced, but the shaft bending increases and rotor-side bearings are damaged during surges
Solution Approach 1:
The patent transitions from axial positioning to radial positioning of the impeller-side bearing. By placing the bearing outside the cover member in the radial direction rather than inside it, the design achieves better shaft support during surges while maintaining compact overall structure. This dimensional change resolves the contradiction between simplicity and reliability.
2Speed
If gas bearings are used for high-speed operation, then the speed increases, but the cost increases
Solution Approach 1:
The patent divides the bearing system into two segments: gas bearings for the impeller-side to enable high-speed operation, and conventional bearings for the rotor-side to control cost. This segmentation allows each part to be optimized for its specific function, achieving high speed where necessary while maintaining cost-effectiveness overall.
3Reliability
If static pressure gas bearings are used for initial load support, then the radial load support at startup is improved, but the device complexity increases
Solution Approach 1:
The patent employs static pressure gas bearings to provide preliminary radial load support during startup before the impeller reaches operating speed. This preliminary action ensures reliable shaft support during the critical startup phase, after which the system transitions to dynamic gas bearing operation, balancing reliability with manageable complexity.
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 enhances operational efficiency, suppresses shaft bending during surges, and allows for higher-speed operation with cost-effective gas bearings, while ensuring radial load support even at startup with static pressure gas bearings.
Implementation Method 1
positions the impeller-side radial bearing outside the cover member to support radial loads, using either gas bearings for high-speed operation
Implementation Method 2
using either gas bearings for high-speed operation or static pressure gas bearings for initial load support
Data Source
AI summary
A centrifugal compressor includes a shaft member and an impeller. The shaft member extends in an axial direction and is rotatable. The impeller includes a hub that is disposed on an end portion of the shaft member, and a plurality of blades disposed on an outer peripheral surface of the hub. The impeller has a shape that tapers outward in the axial direction. A cover member is disposed at least at an end portion of the impeller outside in the axial direction. The cover member is joined to outer peripheries of the plurality of blades in a radial direction and covers at least a part of the plurality of blades from outside in the radial direction. A first bearing is disposed outside in the radial direction of the cover member, the first rotatably supporting the impeller.