Centrifugal Compressor Rotor Mechanism Sealing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Centrifugal compressors face issues with lubricant leakage into the refrigerant loop, contamination of the refrigerant, and inefficient sealing, particularly due to the use of hydrodynamic bearings which are prone to damage and have low efficiency, leading to poor compressor performance and maintenance challenges.
Innovation Solution
A rotor mechanism using a rolling bearing secured by a screw nut and featuring an oil slinger and multiple labyrinth seals to effectively block lubricant leakage and recycle lubricants back to the oil sump, enhancing sealing and compressor efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hydrodynamic bearing is used to support the rotary shaft, then the bearing can provide continuous lubrication, but the lubricant easily leaks into the refrigerant loop causing contamination and the bearing has poor efficiency and low rigidity
Solution Approach 1:
The bearing housing is divided into multiple sealed compartments separated by partition walls. The first compartment contains the hydrodynamic bearing, while the second compartment is separated by a first partition wall with a first oil separator. A second partition wall further divides the space, creating distinct zones for lubrication and refrigerant flow. This segmentation prevents lubricant from mixing with the refrigerant loop while maintaining continuous lubrication in the bearing zone.
Solution Approach 2:
Oil separators are introduced as intermediary components between the bearing compartment and the refrigerant loop. The first oil separator is positioned in the first partition wall, and a second oil separator is positioned in the second partition wall. These intermediaries capture and redirect lubricant droplets that might otherwise leak into the refrigerant stream, allowing the hydrodynamic bearing to function continuously without contaminating the refrigerant.
2Ease of operation
If the pressure difference is not established between bearing regions, then the bearing can operate freely, but the lubricant leaks into the refrigerant loop contaminating the refrigerant purity
Solution Approach 1:
The bearing housing system automatically maintains pressure balance through its internal structure. The partition walls with oil separators create natural pressure zones that self-regulate during operation. When lubricant pressure increases, the oil separators automatically capture and redirect the excess lubricant back to the lubrication system, preventing pressure buildup that would force lubricant into the refrigerant loop. This self-regulating mechanism maintains both bearing operation freedom and refrigerant purity without external control systems.
3Device complexity
If a single impeller is used, then the device complexity is reduced, but the axial force from dorsal pressure difference causes leakage and efficiency loss
Solution Approach 1:
A counter-impeller is introduced to balance the axial forces generated by the main impeller. The counter-impeller rotates in the opposite direction and creates equal and opposite axial thrust, canceling out the net axial force on the rotor assembly. This counterbalancing action eliminates the dorsal pressure difference that causes leakage, allowing the compressor to maintain high efficiency without requiring complex multi-stage impeller configurations.
4Reliability
If the surfaces of hydrodynamic bearings are made extremely soft for lubrication, then the bearing can provide good lubrication, but the surfaces are extremely likely to be damaged when the compressor comes to a sudden halt
Solution Approach 1:
The bearing surface is constructed as a composite structure with a soft lubricating layer bonded to a hard substrate. The soft outer layer (such as babbitt metal or polymer coating) provides excellent lubrication properties and conformability, while the hard underlying structure (such as steel or cast iron) provides mechanical strength and damage resistance. This composite construction allows the bearing to maintain good lubrication during operation while resisting damage during sudden halts or startup conditions.
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 blocks lubricant leakage and refrigerant loss, improves compressor efficiency, and simplifies maintenance by using a more efficient rolling bearing system with labyrinth seals and an oil slinger, reducing contamination and pressure-related issues.
Implementation Method 1
a high-pressure refrigerant is used to drive and guide the lubricant to go from an inlet 102 to an oil sump 101 along the lower border of the casing
Implementation Method 2
the sealing device is used for sealing a transmission region and a motor power region, to reduce drop in efficiency and to prevent the refrigerant from leaking into the motor power region from the transmission region
Implementation Method 3
A jet pump 106 pumps the lubricant to go from an opening 105 to the oil sump 101 via a low-pressure pipe 104
Data Source
AI summary
A rotor mechanism of a centrifugal compressor connectable to a power output device and configured to block leakage of lubricants and to recycle lubricants to an oil sump is provided, which includes a rotary shaft with a rolling bearing and a screw nut, a bearing housing for receiving the rolling bearing, and a bearing plate connected to the bearing housing. The screw nut has a surface provided with an oil throw seal, and the bearing housing. As the bearing plate is provided with an oil channel in contact with the oil-returning hole and either one of the bearing housing and the bearing plate is provided with a first labyrinth seal in contact with the screw nut, lubricants leaking out of the rolling bearing is allowed to go to the oil sump via the oil channel and oil-returning hole. The oil slinger thus blocks the lubricants from leaking out of the first labyrinth seal.