Intermediate Oil Separator for Scroll Compressor Efficiency
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Solution Overview
Problem
In two-stage scroll compressors, lubricating both the first and second stage bearings without reducing compressor efficiency is challenging, as traditional methods like using an oil pump increase power loss and reduce efficiency.
Innovation Solution
The implementation of an oil separator system that entrains oil in the refrigerant stream, separates the oil at intermediate pressure after the first stage of compression, and routes it back to both stages, eliminating the need for a pump and minimizing power input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oil is supplied to second stage bearings by raising pressure through the second stage of compression, then lubrication is provided, but compressor efficiency is reduced
Solution Approach 1:
The oil supply system is segmented into two separate pathways: one for first stage bearings and one for second stage bearings. The first stage bearings are lubricated by oil returned from the oil separator at intermediate pressure, while the second stage bearings are lubricated by oil supplied through the second stage compression process. This segmentation allows each bearing stage to receive appropriate lubrication without forcing oil through the entire compression process, thereby maintaining compressor efficiency.
Solution Approach 2:
The oil separator acts as an intermediary device that receives the refrigerant-oil mixture from the first stage discharge, separates the oil from the refrigerant at intermediate pressure, and returns the separated oil to the first stage bearings. This intermediary function eliminates the need to compress oil to final discharge pressure, reducing the energy penalty while ensuring reliable lubrication.
2Reliability
If an oil pump is attached to the crankshaft to supply oil to both stages, then lubrication is provided, but power loss increases
Solution Approach 1:
The system uses the refrigerant stream itself as the transporting medium for oil from the first stage bearings to the oil separator. The refrigerant flow naturally carries the entrained oil through the interconnecting pipe to the separator, eliminating the need for a separate pump-driven circulation system. The oil is then separated and returned to the bearings, creating a self-service lubrication system that leverages existing refrigerant flow rather than adding additional powered circulation.
3Reliability
If oil is entrained in the refrigerant stream and carried through compression, then lubrication is achieved, but the work required to compress the oil increases
Solution Approach 1:
The oil is extracted from the refrigerant stream at the intermediate pressure point by the oil separator, removing it from the compression process. By taking out the oil at this stage, the system avoids the unnecessary work of compressing the oil through the second stage to final discharge pressure. The separated oil is then returned to the bearings, achieving lubrication without the full energy cost of compressing oil through the entire compression ratio.
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 approach reduces oil circulation rate, maintains efficient lubrication of bearings, and enhances compressor efficiency by avoiding the power-intensive process of compressing oil to final discharge pressure.
Implementation Method 1
An oil separator that is an integral part of the interconnecting pipe removes oil from the refrigerant stream
Implementation Method 2
Oil from the bearings which are in the suction cavity of the scroll compressor is entrained in the refrigerant stream that is entering the first stage of compression
Data Source
AI summary
An oil lubrication system for a multi-stage compressor separates oil from a refrigerant at an intermediate pressure following the first stage of compression and then routes the separated oil at the intermediate pressure to the compressor suction cavity bearings at the intermediate pressure, thus avoiding further compression of oil in subsequent stages of compression. The efficiency of the multi-stage compressor can be increased by not raising the pressure of the oil through the subsequent stages of compression.