Oil-Free Compressor Bearing Cooling Using Ejector-Assisted Pump
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Solution Overview
Problem
Oil-free compressors face challenges in providing startup lubrication due to the non-advantageous positioning of the inlet port of the mechanical pump, which can lead to issues like refrigerant insufficiency and vapor locking, especially during startup conditions.
Innovation Solution
The system incorporates an ejector mechanism that assists in supplying refrigerant to the bearings by using a mechanical pump and an ejector to ensure continuous refrigerant flow, with a controller managing the pump and ejector operations to maintain sufficient fluid pressure and flow, even during startup and shutdown conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the mechanical pump inlet port is positioned conventionally, then the pump structure is simple, but refrigerant supply is insufficient during startup causing vapor locking
Solution Approach 1:
The ejector is activated before the compressor startup to pre-position refrigerant at the pump inlet and bearing locations. This preliminary action ensures that when the compressor starts, refrigerant is already available at critical locations, preventing vapor locking and ensuring immediate bearing lubrication without requiring complex pump inlet positioning modifications.
Solution Approach 2:
The ejector serves as an intermediary device between the refrigerant source and the mechanical pump/bearings. It uses high-pressure motive flow to create a suction effect that draws refrigerant to where it is needed, effectively mediating the refrigerant supply issue without requiring direct modification of the pump structure or inlet positioning.
2Reliability
If refrigerant flow is increased to ensure bearing lubrication, then bearing cooling is improved, but system energy consumption increases
Solution Approach 1:
The ejector utilizes pneumatic principles by using high-pressure refrigerant flow as a motive force to create a suction effect. This hydraulic/pneumatic mechanism moves refrigerant without requiring additional mechanical pumping power, thereby improving bearing cooling effectiveness without increasing pump energy consumption.
Solution Approach 2:
The ejector system is self-powered by utilizing the existing high-pressure refrigerant flow from the compressor discharge or another source within the system. The high-pressure flow automatically drives the ejector mechanism, providing refrigerant supply to bearings without requiring external energy input or additional pump power.
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 reliable lubrication and cooling of bearings by maintaining refrigerant flow, preventing vapor locking and ensuring efficient compressor operation across various conditions, including startup and shutdown phases.
Implementation Method 1
an ejector having a motive flow inlet coupled to the mechanical pump to receive refrigerant from the mechanical pump
Implementation Method 2
A mechanical pump is positioned to drive fluid along the supply flowpath to the one or more bearings
Implementation Method 3
the refrigerant may be directed to the bearings to cool and lubricate the bearings
Data Source
AI summary
A vapor compression system (20) comprises a compressor (22) having one or more bearing systems (66, 68) supporting a rotor and/or one or more working elements (44). One or more bearing feed passages (114) are coupled to the bearings to pass fluid along a supply flowpath to the bearings. A mechanical pump (130; 330) is positioned to drive fluid along the supply flowpath. An ejector (140, 150) has a motive flow inlet (142, 152) coupled to the mechanical pump to receive refrigerant from the mechanical pump.