Multistage Compressor Gas Injection CO2 Cycle Efficiency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing multistage compressors designed for chlorofluorocarbon or HFC refrigerants do not achieve desired compression efficiency and performance when applied to a supercritical CO2 cycle using CO2 refrigerant, as the combination of low-stage and high-stage compression elements does not effectively consider CO2 refrigerant characteristics.
Innovation Solution
A multistage compressor with a low-stage rotary compressing mechanism and a high-stage scroll compressing mechanism, where the pressure ratios and displacement volume ratios of both mechanisms are equivalent, utilizing a gas injection system to inject intermediate pressure CO2 refrigerant gas into the closed housing, minimizing pressure loss and enhancing compression efficiency and COP through an economizer effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a multistage compressor designed for chlorofluorocarbon or HFC refrigerants is applied to a supercritical CO2 cycle, then the basic compression function is achieved, but the compression efficiency and compression performance are insufficient
Solution Approach 1:
The patent changes the key parameter of displacement volume ratio between low-stage and high-stage compression elements from conventional values (1:0.65-1:0.85 for R410A, 1:0.56-1:0.8 for CO2 without injection) to 1:0.85-1:0.95 when gas injection is employed. This parameter adjustment optimizes the compression efficiency specifically for CO2 refrigerant in supercritical cycles with gas injection, resolving the contradiction between maintaining basic compression function and achieving high compression efficiency.
2Productivity
If a gas injection system is added to improve compression performance, then the economizer effect is achieved, but the device complexity increases
Solution Approach 1:
The gas injection system is integrated into the existing multistage compressor structure, where the injected intermediate pressure refrigerant gas serves multiple functions: it cools the compression elements, lubricates the moving parts, and improves compression efficiency through the economizer effect. This multi-functionality approach justifies the added complexity by delivering multiple benefits from a single system addition.
3Productivity
If the displacement volume ratio of low-stage to high-stage compression elements is set to conventional values (1:0.65-1:0.85), then the compressor structure is simple, but the compression efficiency is insufficient for CO2 cycle with gas injection
Solution Approach 1:
The patent specifically adjusts the displacement volume ratio parameter to 1:0.85-1:0.95 for the combination of low-stage rotary compression element and high-stage scroll compression element when gas injection is employed. This optimized ratio ensures that the high-stage element receives sufficient refrigerant gas (including injected gas) while maintaining efficient two-stage compression, achieving high compression efficiency without overly complicating the configuration.
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
The solution achieves high compression performance and COP by minimizing pressure loss and leveraging the low leakage of scroll compressing mechanisms at high pressure differences, ensuring sufficient refrigerant intake and improved two-stage compression efficiency, even with CO2's high dryness function.
Implementation Method 1
minimizing pressure loss and enhancing compression efficiency and COP through an economizer effect
Implementation Method 2
taking intermediate pressure refrigerant gas in the closed housing by the high-stage side scroll compressing mechanism
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
It is an object of the present invention to provide a multistage compressor employing a gas injection system for a CO2 cycle which is able to improve the compression efficiency and the compression performance thereof. In a multistage compressor (2) for a CO2 cycle (1) that carries out two-stage compression by discharging CO2 refrigerant gas compressed in a low-stage side rotary compressing mechanism (4) into a closed housing (3) and taking intermediate pressure refrigerant gas in the closed housing (3) by a high-stage side scroll compressing mechanism (5), a gas injection circuit (15) for injecting intermediate pressure CO2 refrigerant gas extracted from a refrigerant circuit into the closed housing (3) is connected to the closed housing (3), and the pressure ratios of the low-stage side rotary compressing mechanism (4) and the high-stage side scroll compressing mechanism (5) are substantially equivalent, and the ratios of displacement volume are substantially equivalent.