Carbon dioxide transcritical injection refrigeration system and control method

Abstract

The invention relates to the technical field of refrigeration, discloses a carbon dioxide transcritical injection refrigeration system and a control method, solves the problem that an electronic expansion valve stops supplying liquid when the boosting capacity of an injector is insufficient by using a mode of combining gravity liquid supply and direct expansion liquid supply, simplifies the control number of valves in the system operation process, and improves the reliability of the system. The transient load change requirement and the precise control of the outlet pressure of the air cooler are met; the system comprises an ejector, the ejector is connected with a compressor, a gas-liquid separator and an evaporator, and the compressor is connected with the gas-liquid separator so as to suck medium-pressure CO2 gas and compress the medium-pressure CO2 gas to be supercritical; the compressor is further sequentially connected with an oil separator and an air cooler. The air cooler is further connected with the ejector, and a first electric ball valve is installed on a connecting pipeline between the air cooler and the ejector so as to control the optimal pressure of an outlet of the air cooler. The gas-liquid separator is further connected with the evaporator, and a second electric ball valve and an electronic expansion valve are installed on a connecting pipeline between the gas-liquid separator and the evaporator.

Description

Technical Field

[0001] The present invention relates to the field of refrigeration technology, and in particular to a carbon dioxide transcritical injection refrigeration system and a control method. Background Art

[0002] Under typical operating conditions, CO2 refrigeration systems easily enter a transcritical state, with the high-pressure side in the supercritical region and the low-pressure side in the subcritical region. There is a significant pressure difference of 5-8 MPa on both sides. This results in large energy losses in the throttling process of traditional CO2 transcritical refrigeration systems, and the system coefficient of performance (COP) is lower than that of systems using conventional refrigerants, affecting the economic efficiency and market competitiveness of the technology. To break through the energy efficiency bottleneck, replacing high-pressure throttle valves with ejectors has become the mainstream technical solution. Ejectors can recover the kinetic energy of the expansion process, eject low-pressure gas from the evaporator outlet, and increase the suction pressure of the compressor, converting the expansion work into useful work. A large amount of research data shows that this technology can increase the system COP by 10%-30%, bringing new opportunities for the development of CO2 transcritical refrigeration technology.

[0003] However, this technology still has many limitations. In terms of system design, taking the dry direct expansion liquid supply method as an example, the opening of the electronic expansion valve is usually controlled according to the superheat of the evaporator. However, in the carbon dioxide transcritical jet refrigeration system, when the ejector's boosting capacity is insufficient, the pressure difference before and after the electronic expansion valve continues to decrease, which may eventually cause the electronic expansion valve to stop supplying liquid, causing the refrigeration system to paralyze. In order to ensure the reliability of the system, it is often necessary to add valves and pipelines to switch to the conventional compression cycle when the ejector fails, but this undoubtedly increases the complexity of system control and the cost of the unit. In terms of ejector design and control, there are currently two mainstream forms: 1. Adjustable ejector, which dynamically matches the system load changes by adjusting the nozzle throat area, but there are complex structures, high control difficulties and durability issues. 2. Multi-nozzle ejector, which matches the system load changes by connecting multiple groups of fixed-size ejectors in parallel, but the adjustment accuracy is low. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems raised in the above background technology, and then proposes a carbon dioxide transcritical injection refrigeration system and a control method.

[0005] The technical solution adopted by the present invention to solve the technical problem is:

[0006] On the one hand, the present invention proposes a carbon dioxide transcritical ejector refrigeration system, comprising an ejector, which is connected to a compressor, a gas-liquid separator and an evaporator, and the compressor is connected to the gas-liquid separator to inhale medium-pressure CO2 gas and compress it to supercriticality; the compressor is also connected to an oil separator and an air cooler in sequence; the air cooler is also connected to the ejector, and an electric ball valve 1 is installed on the connecting pipeline between the air cooler and the ejector to form medium-pressure gas entering the gas-liquid separator; the gas-liquid separator is also connected to the evaporator, and an electric ball valve 2 and an electronic expansion valve are installed on the connecting pipeline between the gas-liquid separator and the evaporator.

[0007] Furthermore, the above solution opens when the ejector exceeds the working range, and the liquid CO2 flows directly into the evaporator under the action of gravity. The electronic expansion valve opens under normal working conditions of the ejector to control the throttling of the liquid CO2 into the evaporator.

[0008] Furthermore, the above scheme is further provided with a first check valve installed on the connecting pipeline between the gas-liquid separator and the evaporator. When the ejector cannot eject the low-pressure fluid of the evaporator, the low-pressure fluid at the outlet of the evaporator is allowed to flow into the gas-liquid separator. A second check valve is installed on the connecting pipeline between the ejector and the evaporator to prevent the medium-pressure fluid of the gas-liquid separator from flowing back to the evaporator, and the connecting pipeline between the gas-liquid separator and the evaporator is connected to the connecting pipeline between the ejector and the evaporator.

[0009] The above solution goes further, the oil separator is connected to an oil collector, and a solenoid valve 1 and a ball valve are installed on the connecting pipeline between the oil separator and the oil collector. The oil collector is also connected to the compressor, and a solenoid valve 2 and a pressure reducing valve are installed on the connecting pipeline between the oil collector and the compressor.

[0010] The above scheme goes a step further, matching the number of ejectors according to the capacity of the compressor, designing different flow rates for each group of ejectors, and designing the total flow rate of the ejectors to cover the flow rate variation range of the compressor. An electric ball valve is installed in front of each group of ejectors, and the circulation amount of the refrigerant is controlled by adjusting the opening of the electric ball valve, thereby controlling the optimal pressure at the outlet of the air cooler. The switch and opening of the electric ball valve are controlled according to the difference between the actual outlet pressure of the air cooler and the optimal pressure corresponding to the outlet temperature of the air cooler.

[0011] The above solution is further developed, wherein the compressors are arranged in five groups and connected in parallel, and the working flow rate is 0-6000m 3 / h range, and equipped with three sets of ejectors, each set of ejectors has a flow rate of 1000m 3 / h, 2000m 3 / h, 3500m 3 / h, forming eight combinations to control the circulation amount of the system refrigerant.

[0012] The above scheme further adopts that the difference ΔP between the actual outlet pressure of the air cooler and the optimal outlet pressure of the air cooler is within ±2 bar; when ΔP>5 bar, the electric ball valve in front of the injector with the smallest flow rate among the unopened injectors is opened; when 2 bar<ΔP≤5 bar, the electric ball valve in front of the injector with the smallest flow rate among the unopened injectors is gradually opened in steps of 5%; when ΔP<-5 bar, the electric ball valve in front of the injector with the smallest flow rate among the opened injectors is closed; when -5 bar≤ΔP<-2 bar, the electric ball valve in front of the injector with the smallest flow rate among the opened injectors is closed in steps of 5%; when -2 bar<ΔP<-2 bar, the control of the electric ball valve is ended.

[0013] Furthermore, in the above solution, when the ejector is in the applicable range, the evaporation pressure of the evaporator is controlled by the frequency of the compressor and the opening of the electronic expansion valve.

[0014] Furthermore, in the above solution, when the ejector jumps out of the applicable range, the evaporation pressure of the evaporator is controlled by the frequency of the compressor and the opening of the electric ball valve.

[0015] Another aspect of the present invention provides a carbon dioxide transcritical ejector refrigeration method, including an ejector applicable interval control mode and an ejector jump applicable interval control mode;

[0016] In the injector applicable range control mode:

[0017] The second electric ball valve is closed and the electronic expansion valve is opened. The compressor draws in medium-pressure CO2 gas from the gas-liquid separator and compresses it to supercriticality. After passing through the oil separator and air cooler, the high-pressure CO2 enters the ejector and ejects the low-pressure CO2 at the evaporator outlet. The mixed medium-pressure CO2 enters the gas-liquid separator, where the gaseous portion is drawn in by the compressor and the liquid portion is throttled by the electronic expansion valve and enters the evaporator for heat exchange.

[0018] In the injector jump-out applicable range control mode:

[0019] The second electric ball valve opens and the electronic expansion valve closes; the compressor draws in medium-pressure CO2 gas from the gas-liquid separator and compresses it to supercriticality. After passing through the oil separator and air cooler, the high-pressure CO2 is throttled directly to medium pressure in the ejector and enters the gas-liquid separator; the liquid CO2 in the gas-liquid separator enters the evaporator through the second electric ball valve under the action of gravity, and the evaporator gas returns to the gas-liquid separator under the suction of the compressor.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention uses a combination of gravity liquid supply and direct expansion liquid supply to solve the problem of the electronic expansion valve stopping liquid supply when the boosting capacity of the ejector is insufficient. By detecting the pressure and temperature of the primary flow at the secondary flow inlet of the ejector, it is determined whether the current working condition is within the applicable range of the ejector. When it is not within the applicable range of the ejector, the electronic expansion valve is closed and the electric ball valve is opened for gravity liquid supply. When it is detected that the working condition is within the operating range of the ejector, the electric ball valve is closed and the electronic expansion valve is opened for direct expansion liquid supply. This design reduces the valves and pipelines of the traditional design, simplifies the number of valves controlled during system operation, reduces the system volume and cost, has a fast response speed, and meets the needs of transient load changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the present invention;

[0023] Figure 2 This is a schematic diagram of the connection position of the oil collector;

[0024] Figure 3 is a control flow chart of the present invention;

[0025] Among them: 1. Ejector; 2. Compressor; 3. Gas-liquid separator; 4. Evaporator; 5. Oil separator; 6. Air cooler; 7. Electric ball valve 1; 8. Electric ball valve 2; 9. Electronic expansion valve; 10. Check valve 1; 11. Check valve 2; 12. Oil collector; 13. Solenoid valve 1; 14. Ball valve; 15. Solenoid valve 2; 16. Pressure reducing valve. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The present invention is further described in conjunction with the drawings and embodiments:

[0027] On the one hand, the present invention proposes a carbon dioxide transcritical injection refrigeration system. Figure 1As shown, it includes an ejector 1, which is connected to a compressor 2, a gas-liquid separator 3 and an evaporator 4, and the compressor 2 is connected to the gas-liquid separator 3 to inhale medium-pressure CO2 gas and compress it to supercriticality; the compressor 2 is also connected to an oil separator 5 and an air cooler 6 in sequence; the air cooler 6 is also connected to the ejector 1, and an electric ball valve 7 is installed on the connecting pipeline between the air cooler 6 and the ejector 1 to form medium-pressure gas entering the gas-liquid separator 3; the gas-liquid separator 3 is also connected to the evaporator 4, and an electric ball valve 2 8 and an electronic expansion valve 9 are installed on the connecting pipeline between the gas-liquid separator 3 and the evaporator 4. The electric ball valve 2 8 opens when the ejector 1 exceeds the working range, and the liquid CO2 flows directly into the evaporator 4 under the action of gravity. The electronic expansion valve 9 opens under normal operating conditions of the ejector 1 to control the throttling of liquid CO2 into the evaporator 4.

[0028] Among them, a check valve 10 is also installed on the connecting pipeline between the gas-liquid separator 3 and the evaporator 4. When the ejector 1 cannot eject the low-pressure fluid of the evaporator 4, the low-pressure fluid at the outlet of the evaporator 4 is allowed to flow into the gas-liquid separator 3. A check valve 2 11 is installed on the connecting pipeline between the ejector 1 and the evaporator 4 to prevent the medium-pressure fluid of the gas-liquid separator 3 from flowing back to the evaporator 4, ensuring that the flow direction is unique, and the connecting pipeline between the gas-liquid separator 3 and the evaporator 4 is connected to the connecting pipeline between the ejector 1 and the evaporator 4. Under this working condition, the pressure of the gas-liquid separator 3 is medium pressure, so the low-pressure CO2 at the outlet of the evaporator 4 will only flow through the check valve 10, and will not flow through the check valve 2 11. In addition, due to the presence of the check valve 2 11, the medium-pressure gaseous refrigerant of the gas-liquid separator 3 will not flow back to the evaporator 4.

[0029] In addition, refer to the attached Figure 2 As shown, the oil separator 5 is connected to the oil collector 12, and a solenoid valve 13 and a ball valve 14 are installed on the connecting pipeline between the oil separator 5 and the oil collector 12. The oil collector 12 is also connected to the compressor 2, and a solenoid valve 2 15 and a pressure reducing valve 16 are installed on the connecting pipeline between the oil collector 12 and the compressor 2. The oil separator 5 separates the lubricating oil in the exhaust gas of the compressor 2 to prevent the lubricating oil from entering the air cooler 6 and the evaporator 4 and affecting the heat exchange efficiency. The oil collector 12 collects the separated lubricating oil and controls the solenoid valve 2 15 and the pressure reducing valve 16 to return the oil to the compressor 2 to realize the circulation of the lubricating oil.

[0030] When the ejector 1 is in the applicable range, the electric ball valve 2 8 is closed, the electronic expansion valve 9 is opened, the compressor 2 inhales medium-pressure CO2 gas from the gas-liquid separator 3, compresses it to supercriticality, passes through the oil separator 5 and enters the air cooler 6, the high-pressure CO2 (primary flow) coming out of the air cooler 6 enters the ejector 1, and the low-pressure CO2 (secondary flow) at the outlet of the evaporator 4 is ejected, and after mixing, medium-pressure gas is formed, which enters the gas-liquid separator 3, the gas in the gas-liquid separator 3 is sucked out by the compressor 2, and the liquid medium-pressure CO2 is throttled by the electronic expansion valve 9 and enters the evaporator 4 for heat exchange. The gas in the gas-liquid separator 3 is sucked out by the compressor 2, and the liquid medium-pressure CO2 is throttled by the electronic expansion valve 9 and enters the evaporator 4 for heat exchange;

[0031] When the ejector 1 jumps out of the applicable range, the electric ball valve 2 8 opens, the electronic expansion valve 9 closes, the compressor 2 inhales medium-pressure CO2 gas from the gas-liquid separator 3, compresses it to supercriticality, and enters the air cooler 6 through the oil separator 5. The high-pressure CO2 (primary flow) coming out of the air cooler 6 enters the ejector 1. In this state, the ejector 1 cannot eject the CO2 at the outlet of the evaporator 4. The high-pressure CO2 from the air cooler 6 is directly throttled to medium pressure in the ejector 1 and enters the gas-liquid separator 3. The gas in the gas-liquid separator 3 is sucked out by the compressor 2. Under the action of gravity, the liquid medium-pressure CO2 passes through the electric ball valve 2 8 and enters the evaporator 4. The gas in the evaporator 4 returns to the gas-liquid separator 3 under the suction of the compressor 2 and is sucked back by the compressor 2.

[0032] In addition, the number of ejectors 1 is matched according to the capacity of the compressor 2. Each group of ejectors 1 is designed with a different flow rate to ensure that the total flow rate of the ejectors 1 covers the flow rate variation range of the compressor 2. An electric ball valve 7 is installed in front of each ejector 1. By adjusting the opening of the electric ball valve 7, the circulation amount of the refrigerant is controlled, and then the optimal pressure at the outlet of the air cooler 6 is controlled. For example: by connecting five groups of compressors 2 in parallel, the working flow rate is 0-6000m 3 / h range, three groups of ejectors 1 are installed, and the flow rate of each group of ejectors is 1000m 3 / h, 2000m 3 / h, 3500m 3 / h, so there are eight combinations to control the circulation volume of the system refrigerant, as shown in the following table:

[0033]

[0034] During implementation, please refer to the attached Figure 3As shown, the difference ΔP between the actual outlet pressure of the air cooler 6 and the optimal outlet pressure of the air cooler 6 is within ±2 bar; when ΔP>5 bar, the electric ball valve 7 in front of the injector 1 with the smallest flow rate among the unopened injectors 1 is opened (maintained for 10 seconds each time for detection); when 2 bar<ΔP≤5 bar, the electric ball valve 7 in front of the injector 1 with the smallest flow rate among the unopened injectors 1 is gradually opened with a step size of 5%; when ΔP<-5 bar, the electric ball valve 7 in front of the injector 1 with the smallest flow rate among the opened injectors 1 is closed; when -5 bar≤ΔP<-2 bar, the electric ball valve 7 in front of the injector 1 with the smallest flow rate among the opened injectors 1 is closed with a step size of 5%; when -2 bar<ΔP<-2 bar, the control of the electric ball valve 7 is ended.

[0035] In this way, the actual outlet pressure of the system air cooler 6 can be stabilized within the range of ±5 bar of the optimal pressure; controlling multiple groups of ejectors 1 in this way can match the system load changes in real time, with simple and reliable logic, while also ensuring that the difference between the actual outlet pressure of the air cooler 6 and the optimal pressure of the air cooler 6 fluctuates within ±2 bar, further improving the efficiency of the system; and through the dual optimization mechanism of "minimum flow rate priority + last operation valve fine-tuning", rapid and stable pressure regulation is achieved, solving the problems of response lag and insufficient accuracy of traditional methods.

[0036] In addition, when the ejector 1 is in the applicable range, the evaporation pressure of the evaporator 4 is controlled by the frequency of the compressor 2 and the opening of the electronic expansion valve 9; when the ejector 1 jumps out of the applicable range, the evaporation pressure of the evaporator 4 is controlled by the frequency of the compressor 2 and the opening of the electric ball valve 14.

[0037] In addition, another aspect of the present invention provides a carbon dioxide transcritical injection refrigeration control method, including an ejector 1 applicable interval control mode and an ejector 1 jump-out applicable interval control mode;

[0038] In the injector 1 applicable range control mode:

[0039] The electric ball valve 8 is closed and the electronic expansion valve 9 is opened. The compressor 2 draws medium-pressure CO2 gas from the gas-liquid separator 3 and compresses it to supercriticality. After passing through the oil separator 5 and the air cooler 6, the high-pressure CO2 enters the ejector 1 and ejects the low-pressure CO2 at the outlet of the evaporator 4. The mixed medium-pressure CO2 enters the gas-liquid separator 3, the gaseous portion is drawn into the compressor 2, and the liquid portion is throttled by the electronic expansion valve 9 and enters the evaporator 4 for heat exchange.

[0040] In the ejector 1 jumps out of the applicable range control mode: the electric ball valve 2 8 is opened and the electronic expansion valve 9 is closed; the compressor 2 sucks in the medium-pressure CO2 gas from the gas-liquid separator 3 and compresses it to supercriticality. After passing through the oil separator 5 and the air cooler 6, the high-pressure CO2 is directly throttled to the medium pressure in the ejector 1 and enters the gas-liquid separator 3; the liquid CO2 in the gas-liquid separator 3 enters the evaporator 4 through the electric ball valve 2 8 under the action of gravity, and the gas in the evaporator 4 returns to the gas-liquid separator 3 under the suction of the compressor 2.

[0041] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above-described embodiments. The above-described embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A carbon dioxide transcritical ejector refrigeration system, comprising an ejector (1), characterized in that: The ejector (1) is connected to a compressor (2), a gas-liquid separator (3) and an evaporator (4); The compressor (2) is connected to the gas-liquid separator (3) to absorb the medium-pressure CO2 gas and compress it to supercritical pressure; The compressor (2) is also connected in sequence to an oil separator (5) and an air cooler (6); The air cooler (6) is also connected to the ejector (1), and an electric ball valve (7) is installed on the connecting pipeline between the air cooler (6) and the ejector (1) to control the optimal pressure at the outlet of the air cooler (6); The gas-liquid separator (3) is also connected to the evaporator (4), and a second electric ball valve (8) and an electronic expansion valve (9) are installed on the connecting pipeline between the gas-liquid separator (3) and the evaporator (4).

2. The carbon dioxide transcritical jet refrigeration system according to claim 1, characterized in that: The second electric ball valve (8) opens when the ejector (1) exceeds the working range, and the liquid CO2 flows directly into the evaporator (4) under the action of gravity. The electronic expansion valve (9) opens under the normal working condition of the ejector (1) to control the throttling of the liquid CO2 into the evaporator (4).

3. The carbon dioxide transcritical jet refrigeration system according to claim 2, characterized in that: A check valve (10) is also installed on the connecting pipeline between the gas-liquid separator (3) and the evaporator (4) to allow the low-pressure fluid at the outlet of the evaporator (4) to flow into the gas-liquid separator (3) when the ejector (1) is unable to eject the low-pressure fluid from the evaporator (4); A second check valve (11) is installed on the connecting pipeline between the ejector (1) and the evaporator (4) to prevent the medium-pressure fluid of the gas-liquid separator (3) from flowing back to the evaporator (4); Furthermore, the connecting pipeline between the gas-liquid separator (3) and the evaporator (4) is connected to the connecting pipeline between the ejector (1) and the evaporator (4).

4. The carbon dioxide transcritical jet refrigeration system according to claim 3, characterized in that: The oil separator (5) is connected to an oil collector (12), and a solenoid valve (13) and a ball valve (14) are installed on the connecting pipeline between the oil separator (5) and the oil collector (12); The oil collector (12) is also connected to the compressor (2), and a second solenoid valve (15) and a pressure reducing valve (16) are installed on the connecting pipeline between the oil collector (12) and the compressor (2).

5. The carbon dioxide transcritical ejector refrigeration system according to claim 4, characterized in that: The number of ejectors (1) is matched according to the capacity of the compressor (2), and each group of ejectors (1) is designed with a different flow rate, and the design of the total flow rate of the ejectors (1) covers the flow rate variation range of the compressor (2). An electric ball valve (7) is installed in front of each group of ejectors (1). The circulation amount of the refrigerant is controlled by adjusting the opening of the electric ball valve (7), thereby controlling the optimal pressure at the outlet of the air cooler (6). The switch and opening of the electric ball valve (7) are controlled according to the difference between the actual outlet pressure of the air cooler (6) and the optimal pressure corresponding to the outlet temperature of the air cooler (6).

6. The carbon dioxide transcritical jet refrigeration system according to claim 5, characterized in that: The compressors (2) have five groups connected in parallel, and the working flow rate is 0-6000m 3 / h range, and equipped with three sets of ejectors (1), each set of ejector flow is 1000m 3 / h, 2000m 3 / h, 3500m 3 / h, forming eight combinations to control the circulation amount of the system refrigerant.

7. The carbon dioxide transcritical jet refrigeration system according to claim 6, characterized in that: The difference ΔP between the actual outlet pressure of the air cooler (6) and the optimal outlet pressure of the air cooler (6) is within ±2 bar; when ΔP>5 bar, the electric ball valve (7) in front of the injector (1) with the smallest flow rate among the unopened injectors (1) is opened; when 2 bar < ΔP ≤ 5 bar, the electric ball valve (7) in front of the injector (1) with the smallest flow rate among the unopened injectors (1) is gradually opened in 5% steps; when ΔP < -5 bar, the electric ball valve (7) in front of the injector (1) with the smallest flow rate among the opened injectors (1) is closed; when -5 bar ≤ ΔP < -2 bar, the electric ball valve (7) in front of the injector (1) with the smallest flow rate among the opened injectors (1) is closed and gradually closed in 5% steps; when -2 bar < ΔP < -2 bar, the control of the electric ball valve (7) is terminated.

8. The carbon dioxide transcritical jet refrigeration system according to claim 7, characterized in that: When the ejector (1) is in the applicable range, the evaporation pressure of the evaporator (4) is controlled by the frequency of the compressor (2) and the opening of the electronic expansion valve (9).

9. The carbon dioxide transcritical ejector refrigeration system according to claim 8, characterized in that: When the ejector (1) jumps out of the applicable range, the evaporation pressure of the evaporator (4) is controlled by the frequency of the compressor (2) and the opening of the second electric ball valve (8).

10. A carbon dioxide transcritical jet refrigeration control method, characterized in that: It includes an injector (1) applicable interval control mode and an injector (1) jump-out applicable interval control mode; In the injector (1) applicable range control mode: The second electric ball valve (8) is closed, and the electronic expansion valve (9) is opened; the compressor (2) sucks in medium-pressure CO2 gas from the gas-liquid separator (3) and compresses it to supercriticality. After passing through the oil separator (5) and the air cooler (6), the high-pressure CO2 enters the ejector (1) and ejects the low-pressure CO2 at the outlet of the evaporator (4); the mixed medium-pressure CO2 enters the gas-liquid separator (3), the gaseous part is sucked in by the compressor (2), and the liquid part is throttled by the electronic expansion valve (9) and enters the evaporator (4) for heat exchange; In the ejector (1) jump-out applicable range control mode: The electric ball valve 2 (8) is opened and the electronic expansion valve (9) is closed; the compressor (2) sucks in the medium-pressure CO2 gas from the gas-liquid separator (3) and compresses it to supercriticality. After passing through the oil separator (5) and the air cooler (6), the high-pressure CO2 is directly throttled to the medium pressure in the ejector (1) and enters the gas-liquid separator (3); the liquid CO2 in the gas-liquid separator (3) enters the evaporator (4) through the electric ball valve 2 (8) under the action of gravity, and the gas in the evaporator (4) returns to the gas-liquid separator (3) under the suction force of the compressor (2).

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