Compressor Oil Level Retention Using Dual-Mode Gas-Liquid Separation

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Solution Overview

Problem

Rolling rotor compressors are sensitive to wet compression, requiring a specific oil film to maintain lubrication, sealing, and cooling, and existing systems fail to maintain optimal oil levels, leading to damage and reduced efficiency.

Innovation Solution

An automatic oil level retention system with a gas-liquid separator, oil return auxiliary loop, and liquid level detection unit to monitor and control oil levels, ensuring appropriate lubrication and sealing by adjusting oil flow paths based on real-time conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a long oil film sealing line is required for proper lubrication, sealing, and cooling, then excellent oil films are formed on compressor surfaces, but a high lubricating oil liquid level must be maintained which increases the risk of excessive oil entering the refrigeration system

Engineering Contradiction:
Improveoil film sealing qualityVSAvoidlubricating oil liquid level
Core Design Contradiction:
ReliabilityVSQuantity of substance

Solution Approach 1:

The gas-liquid separator is divided into two chambers: a first chamber receiving refrigerant from the compressor and a second chamber receiving refrigerant from the evaporator. This segmentation allows independent oil level control in each chamber, enabling the first chamber to maintain higher oil level for sealing while the second chamber prevents excessive oil accumulation, thus resolving the contradiction between adequate oil sealing and preventing oil overload in the refrigeration system

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

An oil return auxiliary loop with an oil return electromagnetic valve acts as an intermediary mechanism between the two chambers. When the liquid level sensor detects high oil level in the first chamber, the valve opens to transfer excess oil to the second chamber, thereby maintaining optimal oil level for sealing while preventing excessive oil from entering the refrigeration system

Inventive Principle:
Principle #24Intermediary (Mediator)

2Productivity

If the lubricating oil liquid level is reduced to maintain refrigeration efficiency, then heat exchange efficiency is improved, but the lubricating system cannot work normally resulting in abrasion and overheating

Engineering Contradiction:
Improveheat exchange efficiencyVSAvoidlubricating system operation
Core Design Contradiction:
ProductivityVSReliability

Solution Approach 1:

The system dynamically adjusts oil distribution between the two chambers based on real-time liquid level detection. The oil return electromagnetic valve responds to liquid level sensor signals, continuously balancing oil levels to maintain the minimum required level for proper lubrication while allowing the system to operate efficiently, thus resolving the contradiction between heat exchange efficiency and lubricating system reliability

Inventive Principle:
Principle #15Dynamics

3Device complexity

If manual oil level monitoring is used, then system complexity is reduced, but the compressor cannot maintain optimal oil levels leading to damage and reduced efficiency

Engineering Contradiction:
Improveoil level control systemVSAvoidcompressor operation
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

A liquid level sensor provides continuous feedback on the oil level in the first chamber of the gas-liquid separator. When the oil level drops below or rises above the optimal range, the sensor triggers the oil return electromagnetic valve to open or close, automatically adjusting oil flow to maintain the correct level. This feedback mechanism ensures reliable compressor operation without requiring complex manual monitoring systems

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The system is designed to self-regulate oil levels through the automatic control loop consisting of the liquid level sensor, control unit, and oil return electromagnetic valve. The system monitors its own oil level and automatically corrects deviations without external intervention, maintaining optimal lubrication and sealing conditions while preventing damage, thus achieving high reliability with relatively simple device complexity

Inventive Principle:
Principle #25Self-service

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

Maintains optimal oil levels, preventing damage and improving compressor reliability and efficiency by timely adjustment of oil flow, ensuring consistent lubrication and sealing.

Implementation Method 1

the liquid level detection unit is disposed in an inner cavity of the first gas-liquid separator and is configured to monitor lubricating oil liquid level conditions within the first gas-liquid separator in real time

Methodology Applied
Scientific EffectLiquid level detection:

Implementation Method 2

an outlet of the first gas-liquid separator is connected to the compressor body through a gas inlet pipe; an oil return hole of the low-pressure gas-liquid separator is connected to an inlet of the first gas-liquid separator through a gas return pipe

Methodology Applied
Scientific EffectGas-liquid separation:

Implementation Method 3

the oil return auxiliary loop comprises an oil return pipe and an oil return electromagnetic valve disposed on the oil return pipe... on/off of the oil return auxiliary loop is correspondingly controlled according to the lubricating oil liquid level conditions monitored in real time

Methodology Applied
Scientific EffectElectromagnetic valve control: Electromagnet

Implementation Method 4

an outlet of the first gas-liquid separator is connected to the compressor body through a gas inlet pipe... an inlet of the low-pressure gas-liquid separator is provided with an inlet pipe available for being connected by a preset refrigeration system

Methodology Applied
Scientific EffectPressure differential flow: Pressure Gradient

Data Source

PatentEP3929442B1Automatic oil level retention system for compressor and method for controlling same
Publication Date: 2025.11.05 GUANDONG GIWEE TECH CO LTD
  • EP3929442B1 patent drawingFigure 1~2
  • EP3929442B1 patent drawingFigure 3

AI summary

Automatic oil level retention system for a compressor and method for controlling a same, comprising: a normal oil return mode and an auxiliary oil return mode. When a lubricating oil liquid level monitored by a liquid level detection unit (7) in real time is above a required liquid level height, the system initiates only the normal oil return mode; and when the lubricating oil liquid level monitored by the liquid level detection unit (7) in real time is below the required liquid level height, the system initiates the auxiliary oil return mode, and the auxiliary oil return mode is closed and the normal oil return mode is initiated after the lubricating oil liquid level monitored in real time is lifted above the required liquid level height.