Multi-Stage Compressor Injection Switching for Low-Dryness Refrigerant
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Solution Overview
Problem
Multi-stage compressors face issues with liquid compression, suction efficiency degradation, and increased oil circulation ratio due to low dryness of refrigerant and overheating, leading to compression efficiency degradation.
Innovation Solution
A multi-stage compressor with a branching injection circuit and switching mechanism that adjusts injection flow based on refrigerant dryness, injecting refrigerant through different circuits to prevent liquid compression and overheating, and utilizing the electric motor's heat to evaporate liquid refrigerant, while preventing oil circulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the injection circuit is connected to the inside space of the closed housing that is at the same side as the higher stage compression mechanism, then the injection refrigerant can be sucked into the higher stage compression mechanism efficiently, but liquid refrigerant may be sucked into the higher stage compression mechanism causing liquid compression when the dryness of the injection refrigerant is low
Solution Approach 1:
The injection circuit configuration is made dynamic and adjustable based on operating conditions. The switching mechanism dynamically selects between the first circuit (connected to the same side as the higher stage compression mechanism) and the second circuit (connected to the opposite side) according to the dryness of the injection refrigerant, allowing the system to adapt to varying operational states and prevent liquid compression while maintaining suction efficiency.
Solution Approach 2:
The system changes the connection parameter of the injection circuit based on the dryness parameter of the injection refrigerant. When dryness is high, the first circuit is selected for efficient suction; when dryness is low, the second circuit is selected to prevent liquid compression. This parameter-based switching resolves the contradiction between suction efficiency and liquid compression prevention.
2Productivity
If the injection refrigerant is injected into the inside space of the closed housing, then two-stage compression is performed, but the injection refrigerant may be overheated by the electric motor causing suction efficiency degradation
Solution Approach 1:
The invention creates different local injection environments by providing two distinct circuit connections. The first circuit connects to the inside space near the higher stage compression mechanism for efficient suction, while the second circuit connects to the opposite side to avoid the electric motor's heat. The switching mechanism selects the appropriate local environment based on refrigerant dryness, preventing overheating while maintaining compression efficiency.
3Productivity
If the injection refrigerant is injected into the inside space of the closed housing, then two-stage compression is performed, but the lubricating oil may be raised up together with the injection refrigerant causing increased oil circulation ratio
Solution Approach 1:
The invention extracts the harmful effect of oil being raised up with the injection refrigerant by providing an alternative injection path. The second circuit, connected to the opposite side of the electric motor, serves as a separate injection channel that avoids the oil return path. When low dryness is detected, the system switches to this extracted path, preventing oil contamination while maintaining compression function.
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
Prevents liquid compression, improves motor efficiency, enhances compression efficiency, and reduces oil circulation ratio, leading to improved system efficiency.
Implementation Method 1
the intermediate pressure refrigerant gas is discharged into the closed housing... the electric motor... This intermediate pressure refrigerant is heated by the electric motor
Data Source
AI summary
A multi-stage compressor is provided that reliably prevents liquid compression in a higher stage compression mechanism and also prevents compression efficiency degradation resulting from overheating of injection refrigerant and from the lubricating oil being raised up together with the injection refrigerant. An injection circuit is branched into a plurality of circuits. A first circuit thereof is communicatively connected to an inside space of a closed housing that is at the same side as the higher stage compression mechanism with respect to an electric motor, and a second circuit is communicatively connected to an inside space of the closed housing that is opposite from the higher stage compression mechanism with respect to the electric motor. The first circuit and the second circuit are provided with a switching mechanism for switching the injection circuit to the first circuit or the second circuit according to the dryness of the injection refrigerant.