Centrifugal Compressor Sealing and Cooling
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Solution Overview
Problem
High-speed centrifugal compressors face issues with sealing between high-pressure and low-pressure cavities, inadequate internal air cooling leading to poor cooling effects, and challenges in designing thrust air bearings due to complex assembly and deformation issues in existing top-layer foil structures.
Innovation Solution
The design includes a backflow air cooling system with annular slots and a flexible integral top-layer foil structure, enhancing sealing between high-pressure and low-pressure cavities and improving cooling efficiency for all components, while the flexible connection of top-layer foils reduces assembly complexity and deformation-related issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sealing ring is used for sealing between high-pressure cavity and low-pressure cavity, then sealing is achieved, but the sealing ring will be quickly worn and damaged due to high speed exceeding 10000 r/min
Solution Approach 1:
The patent replaces the mechanical sealing ring with a gas seal mechanism. The gas seal uses a thin-walled seal ring with specific structural features (inner diameter, thickness, length ratios) that create a hydrodynamic barrier against gas leakage, eliminating the need for contact-based mechanical sealing that wears at high speeds.
Solution Approach 2:
The patent optimizes the geometric parameters of the seal ring, specifically the ratios of inner diameter, thickness, and length, to achieve effective sealing at high rotational speeds. By changing these dimensional parameters, the seal ring can maintain sealing effectiveness without suffering from the wear problems of traditional mechanical seals.
2Temperature
If external water cooling and internal air cooling are used, then cooling is achieved, but the existing internal air cooling structure has a single internal conduction path and is not reasonable in design, so that only some components can be cooled
Solution Approach 1:
The patent divides the cooling system into multiple independent conduction paths. The first conduction path cools the motor shell and first bearing pedestal, while the second conduction path cools the second bearing pedestal and diffuser. This segmentation allows each path to be optimized for specific components, improving overall cooling effectiveness.
Solution Approach 2:
The patent designs the cooling conduction paths to serve multiple components simultaneously. Each path is configured to cool multiple parts (e.g., motor shell, bearing pedestals, diffuser), making the cooling system more versatile and efficient compared to single-purpose cooling arrangements.
3Stability of the object's composition
If split structure top-layer foil is used, then floatability is good and air film can be fully formed, but assembling process has extremely high requirements and is relatively complicated
Solution Approach 1:
The patent combines multiple top-layer foils into an integrated structure where the foils are pre-positioned and secured within the thrust air bearing assembly. This merging approach maintains the floatability and air film formation capabilities of individual foils while eliminating the complex assembly requirements of separate foil installation.
4Ease of manufacture
If integral structure top-layer foil is used, then positioning and assembling is convenient, but the floatability of the free end is limited too much, affecting the stability of the formed air film
Solution Approach 1:
The patent applies different structural characteristics to different regions of the top-layer foil. The foil is designed with varying thickness, flexibility, or support characteristics in different areas, allowing the root to be securely positioned for easy assembly while the free end maintains sufficient floatability for stable air film formation.
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 solution effectively prevents air leaks between high-pressure and low-pressure cavities, ensures timely heat dissipation, and prolongs the service life of thrust air bearings by improving sealing and cooling efficiency and reducing assembly complexity.
Implementation Method 1
The centrifugal compressor is generally cooled by external water cooling and internal air cooling
Implementation Method 2
All the components can be fully cooled only if a reasonable conduction path for air flowing is formed internally
Implementation Method 3
The air bearing generates an axial bearing force using a compression effect of a wedge-shaped air film between a top-layer foil and a thrust collar
Implementation Method 4
The air bearing generates an axial bearing force using a compression effect of a wedge-shaped air film
Implementation Method 5
A centrifugal air compressor is an energy conversion device to achieve this goal
Data Source
AI summary
A high-speed centrifugal compressor includes a shell, a stator, and a main shaft; a primary bearing pedestal and a secondary bearing pedestal which are used for supporting the main shaft are respectively mounted on inner sides of two ends of the shell; a thrust collar sleeves the main shaft between a primary diffuser and the primary bearing pedestal; one thrust air bearing is arranged on each of two sides of the thrust collar; a radial air bearing is arranged between each of the primary bearing pedestal and the secondary bearing pedestal and the main shaft; a sealing end cover is arranged between the primary worm wheel and the primary diffuser; several annular slots are arranged between the sealing end cover and the primary worm wheel; several annular slots are arranged between the secondary diffuser and the main shaft; and a backflow air cooling system is arranged in the shell.