Compressor Bearing Refrigerant Cooling Through Drain Passages
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Solution Overview
Problem
In oil-free centrifugal compressors, efficiently cooling and lubricating bearings without using oil poses challenges, as refrigerant must be effectively directed and managed to maintain efficiency and prevent interference with heat transfer in refrigeration systems.
Innovation Solution
The implementation of a compressor design with a housing assembly, motor compartment, and ejectors that manage refrigerant flow paths to support the rotor and impellers, utilizing a combination of drain and supply flowpaths to direct refrigerant to bearings for cooling and lubrication, while minimizing energy loss and maintaining high refrigerant concentration to prevent oil interference with heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If refrigerant is directed to bearings for cooling and lubrication in oil-free compressors, then bearing cooling and lubrication is improved, but refrigerant flow management complexity increases
Solution Approach 1:
The refrigerant flow path is segmented into multiple dedicated passages: a first passage directs refrigerant from the suction port to the bearings for cooling and lubrication, while a second passage handles refrigerant flow from the discharge port. This segmentation allows independent optimization of each flow path without interfering with the other, simplifying the overall management complexity while ensuring reliable bearing cooling.
Solution Approach 2:
The patent introduces an intermediary mechanism (the specialized passage system with flow control features) that mediates between the refrigerant flow and the bearings. This intermediary structure manages the refrigerant distribution, ensuring proper cooling and lubrication while preventing direct interference with the main heat transfer paths through the evaporator and condenser.
2Object-generated harmful factors
If refrigerant is used for bearing lubrication instead of oil, then oil interference with heat transfer is eliminated, but refrigerant flow control precision must be increased
Solution Approach 1:
The passage system incorporates local quality features such as varying cross-sectional areas, restriction orifices, and strategic positioning of the refrigerant delivery points near the bearings. These localized structural variations precisely control the refrigerant flow distribution, ensuring adequate cooling and lubrication at the bearings while maintaining high refrigerant concentration in the heat exchangers for effective heat transfer.
Solution Approach 2:
The patent utilizes parameter changes in the refrigerant flow path, including pressure gradients created by the suction and discharge port connections, temperature variations along the flow path, and geometric parameters of the passages themselves. These parameter variations naturally regulate the refrigerant flow to the bearings without requiring complex external control mechanisms, thereby achieving precise flow control while eliminating oil-related heat transfer interference.
3Temperature
If drain passages are positioned to pass fluid to suction housing plenum, then bearing cooling efficiency is improved, but risk of refrigerant carryover increases
Solution Approach 1:
The drain passages are positioned and designed to preliminary separate refrigerant from the lubricant before the mixture reaches the suction housing plenum. The passage geometry and positioning create conditions where refrigerant can be pre-managed or pre-separated, allowing bearing cooling to occur efficiently while preventing refrigerant carryover into the suction line. This preliminary action addresses both the cooling efficiency requirement and the carryover prevention concern.
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 solution ensures efficient cooling and lubrication of bearings in oil-free compressors, enhancing operational efficiency and maintaining effective heat transfer by managing refrigerant flow through various modes of operation based on temperature and pressure conditions, thereby optimizing compressor performance.
Implementation Method 1
one or more drain passages are coupled to the bearings to pass fluid along a drain flowpath from the bearings to a location upstream of the impeller and downstream of the IGV array
Implementation Method 2
refrigerant itself may be directed to the bearings to cool and lubricate the bearings
Implementation Method 3
refrigerant itself may be directed to the bearings to cool and lubricate the bearings
Data Source
AI summary
A compressor (22) has a housing assembly (40) with a suction port (24), a discharge port (26), and a motor compartment (60). An electric motor (42) has a stator (62) within the motor compartment and a rotor (64) within the stator. The rotor is mounted for rotation about a rotor axis (500). One or more working impellers (44) are coupled to the rotor to be driven by the rotor in at least a first condition so as to draw fluid in through the suction port and discharge the fluid from the discharge port. An inlet guide vane (IGV) array (174) is between the suction port (24) and the one or more impellers (44). One or more bearing systems (66, 68) support the rotor (64) and/or the one or more impellers (44). One or more main drain passages (120, 234 206; 120, 232, 202, 206) are coupled to the bearings to pass fluid along a drain flowpath from the bearings to a location (172) upstream of the impeller and downstream of the IGV array.