Rotary Machine Hub Tight Loose Fit Sections
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Solution Overview
Problem
The existing rotary machines face challenges in maintaining stable operation and workability due to radial displacement of the impeller caused by centrifugal force, leading to potential deviations between the impeller and shaft, especially at higher outputs and rotations.
Innovation Solution
A rotary machine design featuring a hub with a tight fit section and a loose fit section, where the tight fit section is fixedly fitted into the shaft near the center of the impeller, and a groove or tapered portions are used to prevent radial widening, ensuring stable contact pressure and suppressing deviations between the impeller and shaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sleeve portion is placed at a position separated from the disc by a length L satisfying the expression (1), then the radial displacement of the impeller due to centrifugal force is suppressed, but the sleeve portion projects from the disc and obstructs the mounting of blades and cover, degrading workability
Solution Approach 1:
The hub is divided into a tight fit section and a loose fit section. The tight fit section is positioned close to the disc to suppress radial displacement and maintain stable operation, while the loose fit section extends outward to avoid obstructing the mounting of blades and cover, thus improving workability.
Solution Approach 2:
The hub extends in the axial direction beyond the disc surface, utilizing the third dimension (axial direction) to resolve the conflict between radial displacement suppression and workability. This allows the tight fit section to remain close to the disc while the loose fit section provides clearance for manufacturing operations.
2Productivity
If the center of the half section of the impeller is placed on the disc side with blades and cover, then the structure is compact, but the sleeve portion is greatly separated from the center and easily extends outward in the radial direction due to centrifugal force, risking deviation between impeller and shaft
Solution Approach 1:
The hub is segmented into tight fit and loose fit sections, allowing the tight fit section to be positioned close to the disc center to resist centrifugal force and prevent deviation, while the loose fit section accommodates the extended geometry needed for high output and rotation performance.
Solution Approach 2:
Different sections of the hub have different fit characteristics. The tight fit section provides strong mechanical coupling to resist centrifugal forces, while the loose fit section provides geometric clearance. This local differentiation allows the impeller to achieve both high performance and stable operation.
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 enhances workability during manufacturing, prevents radial widening of the tight fit section due to centrifugal force, and reliably suppresses deviations between the impeller and shaft, maintaining high performance and strength.
Implementation Method 1
the influence of the radial displacement of the inner diameter of the impeller 201 due to the centrifugal force during rotation to the sleeve portion 205
Implementation Method 2
the sleeve portion 205 easily extends outward in the radial direction due to the centrifugal force of the impeller 201
Data Source
AI summary
A rotary machine includes: a shaft that rotates; a disc that has a substantially cylindrical hub fitted into the shaft and is provided so as to widen outward in a radial direction from a front end to a rear end of the substantially cylindrical hub; and an impeller having a plurality of blades provided on a surface of the disc. The substantially cylindrical hub has a tight fit section having an internal radius that is smaller than a radius of the shaft, and a loose fit section having an internal radius that is greater than the internal radius of the tight fit section. The loose fit section is provided on a front end side of the substantially cylindrical hub with respect to the tight fit section.