Centrifugal Compressor Bearing Seal and Air Flow Management
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Solution Overview
Problem
In centrifugal compressors, air leaks through a gap between the impeller and the housing can cause grease to escape from the bearing, leading to degraded performance due to pressure differences.
Innovation Solution
The design includes opposed holes in the wall portion with larger opening areas than the gap between the shaft and the insertion hole, and a seal ring to reduce air flow through the bearing, directing leaked air back into the motor housing, thereby minimizing grease escape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If air flows through the gap between the impeller and housing due to pressure difference, then air can be delivered to the electric motor side, but grease escapes from the bearing causing performance degradation
Solution Approach 1:
A seal ring is introduced as an intermediary component between the impeller and the housing wall portion. This seal ring intercepts the air flow that would otherwise pass through the bearing, directing it through a dedicated escape hole instead. The seal ring acts as a mediator that separates the air flow path from the bearing, allowing air delivery functionality while protecting the bearing from grease escape.
Solution Approach 2:
The harmful air flow path through the bearing is extracted and redirected through a separate escape hole in the housing wall portion. By providing this alternative path, the air flow that causes grease escape is removed from the bearing region, eliminating the harmful effect while maintaining the pressure difference necessary for air delivery.
2Reliability
If the gap between impeller and housing is reduced to prevent air leakage, then bearing protection improves, but manufacturing precision requirements increase
Solution Approach 1:
The seal ring serves as an intermediary that provides reliable bearing protection without requiring tight gap control. It creates a controlled interface between the impeller and housing, allowing for larger tolerances in the gap dimensions while still effectively managing air flow and protecting the bearing from grease escape.
Solution Approach 2:
The invention changes the approach from controlling the geometric parameter of the gap size to controlling the air flow path through the seal ring and escape hole. This parameter change allows for more relaxed manufacturing tolerances on the gap while achieving the same or better bearing protection效果.
3Reliability
If the bearing is sealed to prevent grease escape, then bearing performance is maintained, but air flow resistance increases
Solution Approach 1:
The escape hole in the housing wall portion acts as an intermediary air passage that bypasses the bearing. This separate path allows air to flow without passing through the bearing, maintaining low flow resistance while the seal ring prevents grease escape. The system separates the air flow function from the bearing lubrication function.
Solution Approach 2:
The air flow path is segmented into two separate channels: one through the seal ring and escape hole for air delivery, and another through the bearing for lubrication. This segmentation allows each component to optimize its function independently, with the bearing focused on lubrication and the escape hole focused on air flow.
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 effectively reduces air flow through the bearing, preventing grease loss and maintaining bearing performance by directing leaked air through the opposed holes, thus enhancing bearing durability and reducing pressure differences.
Implementation Method 1
a bearing (20), which is provided in the insertion hole (2b) or apart from the impeller (22) with respect to the insertion hole (2b), and is configured to axially support the shaft (17) through interposition of grease being a lubricant inside
Implementation Method 2
the air having leaked to the gap formed on the back surface side of the impeller flows out to the electric motor side in accordance with a pressure difference between the diffuser flow passage and the inside of the housing
Data Source
Figure 1
Figure 2~3
AI summary
Provided is a centrifugal compressor, including: a compressor impeller 22 (impeller) which is provided to a shaft 17; a wall portion 2c having an opposed surface 2d that is spaced apart from and opposed to a back surface 22a of the compressor impeller 22; an insertion hole 2b, which is formed in the wall portion 2c, and is configured to receive the shaft 17 inserted to the insertion hole 2b; a ball bearing 20 (bearing), which is provided in the insertion hole 2b or apart from the compressor impeller 22 with respect to the insertion hole 2b, and is configured to axially support the shaft through interposition of grease being a lubricant inside; an electric motor which is provided on a side opposite to the compressor impeller 22 over the wall portion 2c; and an opposed hole 28, which is formed in the wall portion 2c, and has one end 28a opened in the opposed surface 2d and another end 28b opened at a position opposed to a stator of the electric motor on a side opposite to the compressor impeller 22.