Multi-stage compressor and refrigeration system equipped with same
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Solution Overview
Problem
The multi-stage compressor's efficiency is restricted due to overheating of the electric motor, which can lead to reduced operable range, as the injection refrigerant does not pass through the motor when it is overheated, potentially causing liquid compression in the high-stage side compression mechanism.
Innovation Solution
A multi-stage compressor design where a refrigerant supply part selectively injects either a gas or liquid phase of the refrigerant into the electric motor, using a control system to manage the injection based on the motor's temperature, ensuring effective cooling and preventing liquid compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the injection refrigerant is supplied only from the first circuit when the electric motor is overheated, then the electric motor cooling is maintained, but liquid compression may occur in the high-stage side compression mechanism
Solution Approach 1:
The patent implements dynamic switching between two injection circuits based on the electric motor's temperature conditions. When the motor is overheated, the first circuit is activated to provide cooling; when the motor temperature is normal, the second circuit is used to prevent liquid compression. This dynamic adaptation resolves the contradiction by adjusting the injection mode according to real-time thermal conditions.
Solution Approach 2:
The patent changes the parameter of injection refrigerant state (gas phase vs. liquid phase) based on motor temperature. The first circuit supplies gas-phase refrigerant for cooling when the motor is overheated, while the second circuit supplies liquid refrigerant for efficient cooling under normal conditions. This parameter change allows the system to maintain both motor cooling and prevent liquid compression.
2Temperature
If the injection refrigerant passes through the electric motor for cooling, then the motor temperature is reduced, but the operable range is restricted under certain conditions
Solution Approach 1:
The patent segments the injection refrigerant supply into two independent circuits: the first circuit for cooling the electric motor and the second circuit for preventing liquid compression. This segmentation allows the system to independently control the injection mode based on different operational conditions, thereby expanding the operable range while maintaining effective motor cooling.
Solution Approach 2:
The patent employs feedback control by monitoring the electric motor's temperature conditions and automatically selecting the appropriate injection circuit. The switching mechanism responds to temperature feedback, activating the first circuit when overheating is detected and the second circuit under normal conditions, thus adapting to various operational scenarios and expanding the operable range.
3Reliability
If the switching mechanism is added to select between first and second circuits, then the appropriate injection mode is achieved, but the device complexity increases
Solution Approach 1:
The switching mechanism operates autonomously based on the electric motor's temperature conditions without requiring external control. The system self-regulates by automatically selecting the appropriate injection circuit (first or second) according to the thermal state, thereby achieving reliable injection mode selection while minimizing control complexity.
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 design enhances system efficiency by effectively cooling the electric motor using injection refrigerants, expanding the operable range while preventing liquid compression in the high-stage side compression mechanism.
Implementation Method 1
the injection refrigerant is heated by working heat of the electric motor so that a liquid portion is vaporized
Implementation Method 2
a liquid portion is vaporized thus becoming a dried gas refrigerant
Implementation Method 3
the injection refrigerant is heated by working heat of the electric motor so that a liquid portion is vaporized
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
It is an object of the present invention to prevent liquid compression in a high-stage side compression mechanism of a multi-stage compressor, and to effectively cool an electric motor at all times by means of an injection refrigerant thus expanding an operable range. A multi-stage compressor (2) according to the present invention includes: a housing (11) having a sealed container shape; a low-stage side compression mechanism (13) and a high-stage side compression mechanism (14) which are installed in the housing (11); an electric motor (12) which drives the low-stage side compression mechanism (13) and the high-stage side compression mechanism (14), the electric motor (12) being installed in an intermediate pressure zone in the housing (11); an injection nozzle (37) installed into the housing (11) in a penetrating manner so as to face the electric motor (12); and a refrigerant supply part (50) which extracts a gas phase portion and a liquid phase portion of a compressed refrigerant discharged from the high-stage side compression mechanism (14), and selectively supplies the gas phase portion and the liquid phase portion to the injection nozzle (37) as an injection refrigerant.