Centrifugal Compressor Thrust Collar Bolt Fixing Mechanism

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Solution Overview

Problem

In geared centrifugal compressors, the thrust collar can misalign due to reaction forces from the wheel gear, leading to potential axial vibration and instability, especially when shrink fitting is used for attachment, which complicates the suppression of this misalignment.

Innovation Solution

A centrifugal compressor design that includes a thrust collar fixed to the driven shaft using bolts, which are inserted from the opposite side of the wheel gear, allowing the collar to collide with the wheel gear and distribute the reaction force, thereby preventing misalignment without relying on shrink fitting.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If shrink fitting is used to fix the thrust collar to the driven shaft, then the attachment strength is improved, but the misalignment suppression capability deteriorates due to the lifting of the shrink-fitted portion when the thrust collar receives reaction force from the wheel gear

Engineering Contradiction:

Improveattachment strengthVSAvoidmisalignment suppression capability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The fixing mechanism is segmented into multiple bolts distributed around the circumference, with each bolt independently承担ing portion of the thrust force. This segmentation prevents the concentrated stress and lifting that occur with shrink fitting, while maintaining strong attachment and alignment.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Bolts serve as intermediary elements between the thrust collar and driven shaft, providing a flexible yet secure connection. The bolts can accommodate minor dimensional variations and thermal expansion while maintaining reliable attachment, unlike the rigid shrink fit that causes lifting under thrust load.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the thrust collar or driven shaft is lengthened to increase the contact area of the shrink-fitted portion, then the misalignment is suppressed, but the axial vibration in the driven shaft increases

Engineering Contradiction:

Improvemisalignment suppression capabilityVSAvoidaxial vibration

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

Instead of increasing the continuous contact area through lengthening, the thrust force is segmented and distributed across multiple discrete bolt attachment points. This approach provides sufficient misalignment suppression without the excessive axial vibration caused by lengthening the shaft or collar.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The bolts are strategically positioned at specific locations around the circumference where they can effectively resist the thrust force. This local quality approach provides targeted misalignment suppression at the critical bolt attachment points without requiring excessive overall length that would cause vibration.

Inventive Principle:

Principle #3Local quality

3Reliability

If the thrust collar is fixed without shrink fitting, then the misalignment is suppressed, but the attachment reliability deteriorates

Engineering Contradiction:

Improvemisalignment suppression capabilityVSAvoidattachment reliability

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The attachment reliability is segmented across multiple bolts rather than relying on a single shrink fit. This distributed attachment provides both reliable connection and misalignment suppression, as the bolts work together to prevent the thrust collar from moving or misaligning while maintaining strong attachment strength.

Inventive Principle:

Principle #1Segmentation

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 design effectively suppresses thrust collar misalignment and maintains stable operation by distributing the reaction force through bolts, improving maintainability and reducing the risk of axial vibration.

Implementation Method 1

restricting a displacement of the driven shaft in the axial direction by colliding with the wheel gear in the axial direction

Methodology Applied

Scientific EffectMechanical contact force: Mechanical Force

Implementation Method 2

a plurality of bolts disposed at intervals in a circumferential direction around the second central axis and each extending in the axial direction to fix the thrust collar and the pinion gear

Methodology Applied

Scientific EffectMechanical fastening: Mechanical Fastener

Data Source

PatentUS12180969B2Centrifugal compressor

Publication Date: 2024.12.31 MITSUBISHI HEAVY INDUSTIES COMPRESSOR CORP

AI summary

A centrifugal compressor includes: a drive shaft; a wheel gear; a driven shaft; a pinion gear disposed to be rotatable together with the driven shaft, and meshing with the wheel gear; an impeller rotating together with the driven shaft; a thrust collar restricting a displacement of the driven shaft in an axial direction by colliding with the wheel gear in the axial direction; and a plurality of bolts disposed at intervals in a circumferential direction and each extending in the axial direction to fix the thrust collar and the pinion gear. Each of the plurality of bolts fix the thrust collar and the pinion gear in a state where each of the plurality of bolts are inserted from a position opposite to the wheel gear with reference to the thrust collar in the axial direction.