Solid Impeller Centrifugal Compressor Shaftless Rotor Design
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Solution Overview
Problem
Centrifugal compressors face challenges in withstanding high centrifugal forces at elevated rotation speeds due to the concentration of load on thin portions around the shaft hole, leading to potential impeller damage.
Innovation Solution
The design incorporates solid impellers without a central shaft hole, utilizing contact and non-contact surfaces for load distribution and alignment through fitting convex and concave portions, and a balance piston to manage thrust forces, enhancing structural integrity and assembly precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a large shaft hole is formed in the centers of impellers to fix them with a shaft, then the impellers can be assembled and fixed together, but the thin portion around the hole cannot withstand large centrifugal force loads at high rotation speeds
Solution Approach 1:
The patent removes the shaft and shaft hole from the impeller structure entirely. Instead of fixing impellers to a central shaft, the impellers are directly coupled to each other through their outer peripheral surfaces. This extraction of the shaft eliminates the weak thin portion around the hole while maintaining the ability to assemble and fix impellers together through alternative means (direct outer surface coupling with positioning structures).
Solution Approach 2:
Instead of fixing impellers from the inside through a central shaft hole, the patent inverts the approach by fixing impellers from the outside through their outer peripheral surfaces. The coupling mechanism is located at the outer periphery rather than the center, reversing the traditional fixation approach and eliminating the need for a shaft hole that creates structural weakness.
2Reliability
If impellers are fixed by a shaft inserted through large holes, then the impellers can be securely attached, but the load due to centrifugal force concentrates on the thin portion around the hole and increases with rotation speed
Solution Approach 1:
The shaft is completely removed from the system. Impellers are attached directly to each other through their outer peripheral surfaces using positioning structures such as convex-concave fittings or interference fits. This eliminates the load concentration issue at the shaft hole while maintaining secure attachment through distributed contact across the outer periphery of each impeller.
Solution Approach 2:
Positioning structures such as convex-concave fittings or interference fit features are pre-formed on the outer peripheral surfaces of impellers during manufacturing. These positioning structures ensure proper alignment and secure coupling before the impellers are assembled together, preventing misalignment and ensuring reliable attachment without requiring a central shaft.
3Manufacturing precision
If a shaft is used to fix multiple impellers, then the impellers can be aligned and positioned, but the thin portion around the shaft hole cannot withstand the increasing centrifugal force at high speeds
Solution Approach 1:
The shaft is removed entirely, and alignment precision is achieved through positioning structures formed directly on the impeller outer peripheral surfaces. These structures (such as convex-concave fittings or interference fit features) provide precise alignment when impellers are coupled together, eliminating the need for a shaft while maintaining or improving alignment accuracy.
Solution Approach 2:
Positioning structures are pre-formed on the outer peripheral surfaces of impellers during manufacturing with high precision. These structures ensure that when impellers are assembled together, they automatically align correctly without requiring a shaft for positioning. The preliminary formation of these precision features guarantees accurate alignment while avoiding the creation of weak shaft hole portions.
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 significantly improves the impeller's strength against centrifugal forces, allowing stable high-speed operation while reducing the risk of impeller shifting and enhancing assembly workability, thus maintaining torque transmission and rotor stability.
Implementation Method 1
a fluid supplied from the outside through a flow path formed in the casing is compressed by rotations of the impellers
Data Source
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AI summary
A compressor has a rotor. The rotor includes a plurality of impellers that include a disk having a solid structure having a buried center, and are adjacent to each other in an axial direction, and a plurality of bolts for fixing the plurality of impellers together. The disk has a disk surface facing the axial direction and a bolt hole penetrating the disk at a position deviated outward from an axis in a radial direction. The disk surface includes a contact surface of which at least a part is located outside the bolt hole in the radial direction, and a non-contact surface which is a region inside the contact surface in the radial direction.