CN117989739A - Two-stage centrifugal compressor heat pump system - Google Patents

Abstract

The invention relates to the technical field of heat management, in particular to a two-stage centrifugal compressor heat pump system which comprises a low-pressure stage compressor, a high-pressure stage compressor, a low-pressure stage oil separator and a high-pressure stage oil separator. Wherein, the air inlet of the high-pressure stage compressor is communicated with the air outlet of the low-pressure stage compressor. The low-pressure-stage oil separator can supply lubricating oil to the low-pressure-stage compressor and store oil return, and a gas phase chamber in the low-pressure-stage oil separator is communicated with an air inlet of the low-pressure-stage compressor. The high-pressure oil separator can supply lubricating oil to the high-pressure compressor and store oil return, and a gas phase chamber in the high-pressure oil separator is communicated with an air inlet of the high-pressure compressor. Through setting up two oil separators and supplying oil and storing the oil return to low pressure level compressor and high pressure level compressor respectively, can be when unit operation single compressor mode, low pressure level oil separator's pressure can not be too big, and low pressure level compressor can normally return oil, can not lead to the unit to shut down because of the oil return is blocked.

Description

Two-stage centrifugal compressor heat pump system

Technical Field

The invention relates to the technical field of heat management, in particular to a two-stage centrifugal compressor heat pump system.

Background

The two-stage centrifugal compressor heat pump system comprises a high-pressure stage compressor and a low-pressure stage compressor, gear drive systems at the gear box sides of the two-stage compressors are required to be lubricated, and lubricating oil flows back to an external oil groove through an oil return port. When such a conventional lubrication unit is applied to a two-stage centrifugal compressor heat pump system, if the high-pressure stage compressor and the low-pressure stage compressor share one external oil tank, a problem of oil return blockage occurs in a single compressor operation mode, resulting in abnormal shutdown of the unit report. Specifically, when the unit operates in a single compressor mode, namely the low-pressure stage compressor operates, and the high-pressure stage compressor does not operate, because the exhaust port of the low-pressure stage compressor is directly communicated with the air suction port of the high-pressure stage compressor, the air suction port of the high-pressure stage compressor is also in a high-pressure state, high-pressure air flows from the impeller side of the high-pressure stage compressor to the gear box side and flows into the external oil groove along the oil return pipe of the high-pressure stage compressor, the pressure in the external oil groove is continuously increased, finally, oil in the gear box and the oil return pipe of the low-pressure stage compressor cannot flow into the external oil groove, namely the oil return is blocked, the oil in the external oil groove is less and less, and the unit is abnormally stopped.

Accordingly, there is a need for a two-stage centrifugal compressor heat pump system that addresses the above-described issues.

Disclosure of Invention

The invention aims at: the heat pump system of the two-stage centrifugal compressor can ensure that the low-pressure stage compressor can return oil normally when a unit runs in a single-compressor mode, and solves the problem that the unit is stopped due to the blocking of oil return.

To achieve the purpose, the invention adopts the following technical scheme:

there is provided a two-stage centrifugal compressor heat pump system comprising:

A low pressure stage compressor;

The air inlet of the high-pressure stage compressor is communicated with the air outlet of the low-pressure stage compressor;

The low-pressure-stage oil separator can supply lubricating oil to the low-pressure-stage compressor and store oil return, and a gas phase chamber in the low-pressure-stage oil separator is communicated with an air inlet of the low-pressure-stage compressor;

The high-pressure oil separator can supply lubricating oil to the high-pressure compressor and store oil return, and a gas phase chamber in the high-pressure oil separator is communicated with an air inlet of the high-pressure compressor.

As a preferable scheme of the two-stage centrifugal compressor heat pump system, the system further comprises a first oil way and a first one-way valve, wherein two ends of the first oil way are respectively communicated with an oil cavity of the low-pressure stage oil separator and an oil cavity of the high-pressure stage oil separator, and the first one-way valve is arranged on the first oil way so that the trend of lubricating oil in the first oil way is from the high-pressure stage oil separator to the low-pressure stage oil separator;

And/or, the oil pump and the second one-way valve are arranged on the second oil path, so that the trend of lubricating oil in the second oil path is from the low-pressure-stage oil separator to the high-pressure-stage oil separator.

As a preferred scheme of the two-stage centrifugal compressor heat pump system, the system further comprises a liquid storage tank, wherein the liquid storage tank can release the refrigerant when the two-stage centrifugal compressor heat pump system is switched to a refrigerating mode and store the refrigerant when the two-stage centrifugal compressor heat pump system is switched to a heating mode.

As a preferred scheme of the two-stage centrifugal compressor heat pump system, the system further comprises a four-way reversing valve, a wind side heat exchanger, a water side heat exchanger and an economizer heat exchanger, wherein a D port of the four-way reversing valve is selectively communicated with an exhaust port of the low-pressure stage compressor and an exhaust port of the high-pressure stage compressor, a C port of the four-way reversing valve is communicated with one port of the wind side heat exchanger, the other port of the wind side heat exchanger is communicated with one port of the first side of the economizer heat exchanger, the other port of the first side of the economizer heat exchanger is communicated with one port of the first side of the water side heat exchanger, the other port of the first side of the water side heat exchanger is communicated with an E port of the four-way reversing valve, and an S port of the four-way reversing valve is communicated with an air inlet of the low-pressure stage compressor.

As a preferred embodiment of the two-stage centrifugal compressor heat pump system, one port on the second side of the economizer heat exchanger is selectively in communication with the inlet port of the high pressure stage compressor.

As a preferable scheme of the two-stage centrifugal compressor heat pump system, the liquid inlet of the liquid storage tank can be selectively communicated with the other port of the wind side heat exchanger, the gas phase chamber of the liquid storage tank can be selectively communicated with a communication pipeline between the air inlet of the high-pressure stage compressor and one port of the second side of the economizer heat exchanger, and the liquid outlet of the liquid storage tank can be selectively communicated with one port of the first side of the water side heat exchanger.

As a preferred scheme of the two-stage centrifugal compressor heat pump system, the system further comprises a first liquid level sensor, wherein the first liquid level sensor is used for measuring the liquid level of the low-pressure-stage oil separator;

and/or, further comprising a second liquid level sensor for measuring the liquid level of the high-pressure stage oil separator;

and/or, the device further comprises a third liquid level sensor, wherein the third liquid level sensor is used for measuring the liquid level of the liquid storage tank.

As a preferred scheme of the two-stage centrifugal compressor heat pump system, the system further comprises a low-pressure oil cooler, wherein the inlet end of the first side of the low-pressure oil cooler is communicated with the oil outlet end of the low-pressure oil cooler, and the outlet end of the first side of the low-pressure oil cooler is communicated with the oil inlet of the gear box of the low-pressure compressor;

The high-pressure oil cooler is characterized by further comprising a high-pressure oil cooler, wherein the inlet end of the first side of the high-pressure oil cooler is communicated with the oil outlet end of the high-pressure oil cooler, and the outlet end of the first side of the high-pressure oil cooler is communicated with the oil inlet of the gear box of the high-pressure compressor.

As a preferred scheme of the two-stage centrifugal compressor heat pump system, the system further comprises a low-pressure stage oil filter, wherein the low-pressure stage oil filter is arranged on a pipeline between an outlet end of a first side of the low-pressure stage oil cooler and an oil inlet of a gear box of the low-pressure stage compressor;

The high-pressure oil cooler is characterized by further comprising a high-pressure level oil filter, wherein the high-pressure level oil filter is arranged on a pipeline between the outlet end of the first side of the high-pressure level oil cooler and the oil inlet of the gear box of the high-pressure level compressor.

As a preferred scheme of the two-stage centrifugal compressor heat pump system, the system further comprises a first three-way valve, wherein a first end of the first three-way valve is communicated with an oil outlet end of the low-pressure stage oil separator, a second end of the first three-way valve is communicated with an outlet end of a first side of the low-pressure stage oil cooler, and a third end of the first three-way valve is communicated with an inlet of the low-pressure stage oil filter;

The high-pressure oil filter further comprises a second three-way valve, wherein the first end of the second three-way valve is communicated with the oil outlet end of the high-pressure oil separator, the second end of the second three-way valve is communicated with the outlet end of the first side of the high-pressure oil cooler, and the third end of the second three-way valve is communicated with the inlet of the high-pressure oil filter.

The invention has the beneficial effects that:

The invention provides a two-stage centrifugal compressor heat pump system which comprises a low-pressure stage compressor, a high-pressure stage compressor, a low-pressure stage oil separator and a high-pressure stage oil separator. Wherein, the air inlet of the high-pressure stage compressor is communicated with the air outlet of the low-pressure stage compressor. The low-pressure-stage oil separator can supply lubricating oil to the low-pressure-stage compressor and store oil return, and a gas phase chamber in the low-pressure-stage oil separator is communicated with an air inlet of the low-pressure-stage compressor. The high-pressure oil separator can supply lubricating oil to the high-pressure compressor and store oil return, and a gas phase chamber in the high-pressure oil separator is communicated with an air inlet of the high-pressure compressor. Through setting up two oil separators and supplying oil and storing the oil return to low pressure level compressor and high pressure level compressor respectively, can be when unit operation single compressor mode, low pressure level oil separator's pressure can not be too big, and low pressure level compressor can normally return oil, can not lead to the unit to shut down because of the oil return is blocked.

Drawings

FIG. 1 is a schematic diagram of a two-stage centrifugal compressor heat pump system according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a single stage refrigeration mode of a two-stage centrifugal compressor heat pump system provided by an embodiment of the present invention;

FIG. 3 is a schematic diagram of a two-stage compression refrigeration mode of a two-stage centrifugal compressor heat pump system provided by an embodiment of the present invention;

FIG. 4 is a schematic diagram of a two-stage compression heating mode of a two-stage centrifugal compressor heat pump system provided by an embodiment of the invention;

FIG. 5 is a schematic diagram of a cooling, switching and heating intermediate mode of a two-stage centrifugal compressor heat pump system according to an embodiment of the present invention;

fig. 6 is a schematic diagram of a heating, switching and refrigerating intermediate mode of a two-stage centrifugal compressor heat pump system according to an embodiment of the present invention.

In the figure:

1. A low pressure stage compressor; 2. a high pressure stage compressor; 3. a water side heat exchanger; 4. a wind side heat exchanger; 5. an economizer heat exchanger; 6. a four-way reversing valve; 7. a gas-liquid separator; 8. a low pressure stage oil separator; 9. high-pressure-stage oil separator; 10. drying the filter; 11. a liquid storage tank; 12. a low-pressure stage oil cooler; 13. a high-pressure stage oil cooler; 14. a low pressure stage oil filter; 15. a high pressure stage oil filter; 16. an oil pump; 17. a second three-way valve; 18. a first three-way valve; 19. a third liquid level sensor; 20. a second liquid level sensor; 21. a first liquid level sensor; 22. a first oil passage; 23. a second oil path;

31. A third one-way valve; 32. a fourth one-way valve; 33. a first drain solenoid valve; 34. a refrigeration one-way valve; 35. a heating one-way valve; 36. a liquid path stop valve; 37. heating EEV; 38. a second drain solenoid valve; 39. a third liquid discharge electromagnetic valve; 40. refrigerating EEV; 41. an economizer EEV; 42. a liquid discharge one-way valve; 43. an economizer check valve; 44. a first one-way valve; 45. a second one-way valve; 46. a first electromagnetic valve;

51. Suction pressure and temperature sensors; 52. low pressure stage exhaust pressure and temperature sensors; 53. high pressure stage exhaust pressure and temperature sensors; 54. low pressure stage oil supply pressure and temperature sensors; 55. high pressure stage oil supply pressure and temperature sensors; 56. a low pressure stage sump pressure sensor; 57. a high pressure stage sump pressure sensor; 58. liquid phase pressure and temperature sensors; 59. and an economizer make-up gas pressure and temperature sensor.

Detailed Description

The technical scheme of the invention is further described below with reference to the attached drawings and the embodiments. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting thereof. It should be further noted that, for convenience of description, only some, but not all of the drawings related to the present invention are shown.

In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixed or removable, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.

In the present invention, unless expressly stated or limited otherwise, a first feature "above" or "below" a second feature may include both the first and second features being in direct contact, as well as the first and second features not being in direct contact but being in contact with each other through additional features therebetween. Moreover, a first feature being "above," "over" and "on" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicating that the first feature is higher in level than the second feature. The first feature being "under", "below" and "beneath" the second feature includes the first feature being directly under and obliquely below the second feature, or simply means that the first feature is less level than the second feature.

As shown in fig. 1, the two-stage centrifugal compressor heat pump system of the present embodiment includes a low-pressure stage compressor 1, a high-pressure stage compressor 2, a low-pressure stage oil separator 8, and a high-pressure stage oil separator 9. Wherein the inlet of the high-pressure stage compressor 2 is communicated with the outlet of the low-pressure stage compressor 1. The low-pressure stage oil separator 8 can supply lubricating oil to the low-pressure stage compressor 1 and store return oil, and a gas phase chamber in the low-pressure stage oil separator 8 is communicated with an air inlet of the low-pressure stage compressor 1. The high-pressure stage oil separator 9 can supply lubricating oil to the high-pressure stage compressor 2 and store return oil, and a gas phase chamber in the high-pressure stage oil separator 9 is communicated with an air inlet of the high-pressure stage compressor 2.

Through setting up two oil separators and supplying oil and storing the oil return to low pressure level compressor 1 and high pressure level compressor 2 respectively, can be when unit operation list compressor mode, the pressure of low pressure level oil separator 8 can not be too big, and low pressure level compressor 1 can normally return oil, can not lead to the unit to shut down because of the oil return is obstructed. The pressure of the high-pressure-stage oil separator 9 of the high-pressure-stage compressor 2 is balanced to the volute intake pressure of the high-pressure-stage compressor 2, and the pressure of the low-pressure-stage oil separator 8 of the low-pressure-stage compressor 1 is balanced to the volute intake pressure of the low-pressure-stage compressor 1, so that the respective oil supply pressure is ensured to be higher than the oil groove pressure, namely, the oil suction pressure is higher than the suction pressure of the respective compressor by 250kpa, the lubricating oil can be ensured to normally flow into the compressor, the lubricating oil can be normally returned, and the normal operation of the compressor is ensured.

In order to facilitate the adjustment of the oil amounts in the two oil separators, the two-stage centrifugal compressor heat pump system preferably further comprises a first oil passage 22 and a first check valve 44, wherein two ends of the first oil passage 22 are respectively communicated with the oil chamber of the low-pressure stage oil separator 8 and the oil chamber of the high-pressure stage oil separator 9, and the first check valve 44 is arranged on the first oil passage 22 so that the lubricating oil in the first oil passage 22 runs from the high-pressure stage oil separator 9 to the low-pressure stage oil separator 8.

Preferably, the first oil passage 22 is further provided with a first solenoid valve 46 for controlling whether the lubricating oil is circulated or not, and for regulating the flow rate of the lubricating oil in the circulated state. When the oil level in the high-pressure stage oil separator 9 is higher than the normal level, and the oil level in the low-pressure stage oil separator 8 is lower than the normal level, the first electromagnetic valve 46 may be opened to allow the lubricating oil to flow from the high-pressure stage oil separator 9 to the low-pressure stage oil separator 8.

Preferably, the two-stage centrifugal compressor heat pump system further comprises a second oil path 23, an oil pump 16 and a second check valve 45, wherein two ends of the second oil path 23 are respectively communicated with the oil cavity of the low-pressure stage oil separator 8 and the oil cavity of the high-pressure stage oil separator 9, and the oil pump 16 and the second check valve 45 are arranged on the second oil path 23 so that the lubricating oil in the second oil path 23 flows from the low-pressure stage oil separator 8 to the high-pressure stage oil separator 9. When the oil level in the low-pressure-stage oil separator 8 is higher than the normal level and the oil level in the high-pressure-stage oil separator 9 is lower than the normal level, the oil pump 16 is turned on to pump the lubricating oil from the low-pressure-stage oil separator 8 to the high-pressure-stage oil separator 9.

The two-stage centrifugal compressor heat pump system has different refrigerant filling amounts under the refrigerating mode and the heating mode, and takes a 15kW air-cooled heat pump unit with a certain typical design as an example. The finned tube heat exchanger used a 600×600 size microchannel heat exchanger having a capacity of 1.32L, and used for refrigerating 1.25kg of refrigerant stored in the condenser and heating 0.55kg of refrigerant stored in the evaporator. The evaporator adopts two plate evaporators, the total volume of the two plate evaporators is 0.54L, and 0.22kg of refrigerant stored when the two plate evaporators are used for refrigerating the evaporator; 0.52kg of refrigerant stored in the condenser and 0.21kg of refrigerant in the liquid pipe were heated. The total refrigerant charge in the cooling mode is 1.25+0.22+0.21=1.68 kg; the total refrigerant charge in the heating mode was 0.55+0.52+0.21=1.28 kg. I.e., the refrigerant charge required for the cooling mode and the heating mode, is different, it is necessary to store and release the refrigerant of the phase difference required for the two modes to ensure reliable operation in each mode. It is therefore preferred that the two-stage centrifugal compressor heat pump system further comprises a liquid storage tank 11, the liquid storage tank 11 being capable of releasing the refrigerant when the two-stage centrifugal compressor heat pump system is switched to the cooling mode and storing the refrigerant when switched to the heating mode. Alternatively, the reservoir 11 is a medium pressure reservoir.

Preferably, the two-stage centrifugal compressor heat pump system further comprises a four-way reversing valve 6, a wind side heat exchanger 4, a water side heat exchanger 3 and an economizer heat exchanger 5. Alternatively, the wind side heat exchanger 4 is a fin tube heat exchanger.

The D port of the four-way reversing valve 6 is selectively communicated with the exhaust port of the low-pressure stage compressor 1 and the exhaust port of the high-pressure stage compressor 2. In order to facilitate control of the selective communication, optionally, a third check valve 31 is provided on the communication line of the D port with the discharge port of the low-pressure stage compressor 1, and a fourth check valve 32 is provided on the communication line of the D port with the discharge port of the high-pressure stage compressor 2.

The C port of the four-way reversing valve 6 is connected to one port of the wind side heat exchanger 4, and the other port of the wind side heat exchanger 4 is connected to one port of the first side of the economizer heat exchanger 5. Optionally, a drier-filter 10 is also arranged between the wind side heat exchanger 4 and the economizer heat exchanger 5. Optionally, a refrigerating check valve 34 and a liquid path stop valve 36 are sequentially arranged on a pipeline between the wind side heat exchanger 4 and the dry filter 10.

The other port of the first side of the economizer heat exchanger 5 is connected to one port of the first side of the water side heat exchanger 3, optionally with a refrigeration EEV (electronic expansion valve ) 40 disposed in the connection line therebetween.

The other port of the first side of the water side heat exchanger 3 is communicated with the E port of the four-way reversing valve 6, and the S port of the four-way reversing valve 6 is communicated with the air inlet of the low-pressure stage compressor 1. Optionally, a gas-liquid separator 7 is also provided between the S port and the inlet of the low pressure stage compressor 1.

Preferably, one port of the second side of the economizer heat exchanger 5 is selectively communicable with the inlet port of the high pressure stage compressor 2. Optionally, an economizer check valve 43 is provided on the communication line between one port of the second side of the economizer heat exchanger 5 and the intake port of the high pressure stage compressor 2 to control the flow direction of the refrigerant from the economizer heat exchanger 5 to the intake port of the high pressure stage compressor 2. The other port of the second side of the economizer heat exchanger 5 is selectively communicated with the other port of the first side of the economizer heat exchanger 5, and an economizer EEV41 is provided on the communicating pipe.

Preferably, the liquid inlet of the liquid storage tank 11 can be selectively communicated with the other port of the wind side heat exchanger 4, and a first liquid discharge electromagnetic valve 33 is arranged on a communicating pipeline between the two. Preferably, the gas phase chamber of the liquid storage tank 11 is selectively communicated with a communication pipeline between the gas inlet of the high-pressure stage compressor 2 and one port on the second side of the economizer heat exchanger 5. Optionally, the other end of the first line communicating with the gas phase chamber of the liquid storage tank 11 is connected to the line upstream of the economizer check valve 43, and a third drain solenoid valve 39 is provided on the first line. Preferably, the liquid outlet of the liquid storage tank 11 is selectively communicated with one port on the first side of the water side heat exchanger 3, and a second liquid discharge electromagnetic valve 38 and a liquid discharge one-way valve 42 are sequentially arranged on a communicating pipeline between the liquid storage tank 11 and the water side heat exchanger to control the refrigerant to flow from the liquid storage tank 11 to the water side heat exchanger 3 so as to supplement the refrigerant when the operation mode is switched.

In order to facilitate the detection of the liquid level, the two-stage centrifugal compressor heat pump system preferably further comprises a first liquid level sensor 21, the first liquid level sensor 21 being adapted to measure the liquid level of the low-pressure stage oil separator 8. Preferably, the two-stage centrifugal compressor heat pump system further comprises a second liquid level sensor 20, the second liquid level sensor 20 being for measuring the liquid level of the high-pressure stage oil separator 9. Preferably, the two-stage centrifugal compressor heat pump system further comprises a third liquid level sensor 19, the third liquid level sensor 19 being for measuring the liquid level of the liquid storage tank 11.

In order to facilitate regulation of the temperature of the lubricating oil injected into the compressor, the two-stage centrifugal compressor heat pump system preferably further comprises a low-pressure stage oil cooler 12, wherein the inlet end of the first side of the low-pressure stage oil cooler 12 is communicated with the oil outlet end of the low-pressure stage oil separator 8, and the outlet end of the first side of the low-pressure stage oil cooler 12 is communicated with the oil inlet port of the gear box of the low-pressure stage compressor 1. Preferably, the two-stage centrifugal compressor heat pump system further comprises a high-pressure stage oil cooler 13, wherein an inlet end of a first side of the high-pressure stage oil cooler 13 is communicated with an oil outlet end of the high-pressure stage oil separator 9, and an outlet end of the first side of the high-pressure stage oil cooler 13 is communicated with an oil inlet of a gear box of the high-pressure stage compressor 2.

Optionally, heaters are arranged in the oil cavities of the two oil separators to heat the lubricating oil and ensure the oil temperature of the output lubricating oil. The output ports of the two heaters are respectively communicated with the inlet ends of the first sides of the two oil coolers.

Alternatively, the inlet end of the second side of the high-pressure stage oil cooler 13 and the inlet end of the second side of the low-pressure oil cooler are both connected to a pipe downstream of the dry filter 10, so that the refrigerant downstream of the dry filter 10 is fed into the oil cooler for heat exchange and temperature adjustment with the lubricating oil. Alternatively, the outlet end of the second side of the high-pressure stage oil cooler 13 and the outlet end of the second side of the low-pressure oil cooler are both communicated with a line upstream of the gas-liquid separator 7, so that the refrigerant after heat exchange is fed upstream of the gas-liquid separator 7.

For filtering the lubrication oil injected into the compressor, the two-stage centrifugal compressor heat pump system preferably further comprises a low pressure stage oil filter 14, the low pressure stage oil filter 14 being arranged in a line between the outlet end of the first side of the low pressure stage oil cooler 12 and the oil inlet of the gearbox of the low pressure stage compressor 1. The two-stage centrifugal compressor heat pump system further comprises a high-pressure stage oil filter 15, the high-pressure stage oil filter 15 being arranged on a line between the outlet end of the first side of the high-pressure stage oil cooler 13 and the oil inlet of the gearbox of the high-pressure stage compressor 2.

In order to facilitate further control of the oil temperature of the lubricating oil input to the compressor, the two-stage centrifugal compressor heat pump system preferably further comprises a first three-way valve 18, a first end of the first three-way valve 18 is communicated with the oil outlet end of the low-pressure stage oil separator 8, a second end of the first three-way valve 18 is communicated with the outlet end of the first side of the low-pressure stage oil cooler 12, and a third end of the first three-way valve 18 is communicated with the inlet of the low-pressure stage oil filter 14. The two-stage centrifugal compressor heat pump system further comprises a second three-way valve 17, wherein a first end of the second three-way valve 17 is communicated with an oil outlet end of the high-pressure stage oil separator 9, a second end of the second three-way valve 17 is communicated with an outlet end of the first side of the high-pressure stage oil cooler 13, and a third end of the second three-way valve 17 is communicated with an inlet of the high-pressure stage oil filter 15.

Optionally, the other output of the first side of the water side heat exchanger 3 is connected via a second line to the line between the refrigeration check valve 34 and the liquid line shut-off valve 36 to enable the refrigerant to flow from the water side heat exchanger 3 to the economizer heat exchanger 5 via the drier-filter 10 in the heating mode. A heating check valve 35 is provided on the second line to control the flow direction of the refrigerant.

Optionally, another port on the first side of the economizer heat exchanger 5 is in communication with another port of the wind side heat exchanger 4 via a third line, on which a heating EEV37 is disposed.

For monitoring the pressure and temperature of the system, optionally, a suction pressure and temperature sensor 51 is provided on the downstream line of the gas-liquid separator 7, a low-pressure stage discharge pressure and temperature sensor 52 is provided on the downstream line of the discharge port of the low-pressure stage compressor 1, a high-pressure stage discharge pressure and temperature sensor 53 is provided on the downstream line of the discharge port of the high-pressure stage compressor 2, a low-pressure stage oil supply pressure and temperature sensor 54 is provided on the lubricating oil input line of the low-pressure stage compressor 1, and a high-pressure stage oil supply pressure and temperature sensor 55 is provided on the lubricating oil input line of the high-pressure stage compressor 2. A low-pressure stage oil tank pressure sensor 56 is provided at the gas-phase chamber of the low-pressure stage oil separator 8 to measure the pressure of the gas-phase chamber of the low-pressure stage oil separator 8, and a high-pressure stage oil tank pressure sensor 57 is provided at the gas-phase chamber of the high-pressure stage oil separator 9 to measure the pressure of the gas-phase chamber of the high-pressure stage oil separator 9. A liquid phase pressure and temperature sensor 58 is provided in the downstream line of the drier filter 10 and an economizer make-up gas pressure and temperature sensor 59 is provided in the downstream line of one port on the second side of the economizer heat exchanger 5.

Fig. 2 is a schematic diagram of a single-stage refrigeration mode, and fig. 3 is a schematic diagram of a two-stage compression refrigeration mode. In the single-machine cooling mode, the high-pressure stage compressor 2 is not put into operation, so that the oil supply pipeline system is also in a closed state, and the high-pressure stage oil cooler 13, the second three-way valve 17 and the high-pressure stage oil filter 15 are not operated. When the high-pressure stage compressor 2 is not in operation, the refrigerant discharged from the discharge port of the low-pressure stage compressor 1 enters the D port of the four-way reversing valve 6 through the third check valve 31, and the high-pressure stage compressor 2 is bypassed. Therefore, the system allows the low-pressure stage compressor 1 to independently operate, if the system needs to switch to the two-stage compression refrigeration mode to operate the two-stage compression refrigeration cycle, only the high-pressure stage compressor 2 needs to be started, the high-pressure stage compressor 2 sucks gas from the exhaust port of the low-pressure stage compressor 1, meanwhile, the middle air supplementing of the economizer heat exchanger 5 enters the air suction port of the high-pressure stage compressor 2, the exhaust gas of the high-pressure stage compressor 2 enters the pipeline of the fourth one-way valve 32, the third one-way valve 31 is reversely cut off, and the system stably operates in the two-stage compression refrigeration mode.

When the unit is operated in the two-stage compression cooling mode shown in fig. 3 and the single-stage cooling mode shown in fig. 2, if it is required to switch to the heating mode, the first drain solenoid valve 33 is opened according to the switching of the cooling and heating intermediate mode shown in fig. 5, a part of the liquid-phase refrigerant is transferred into the liquid tank 11 by the high pressure of the wind side heat exchanger 4, and the liquid level is controlled by the third liquid level sensor 19, and the difference between the refrigerant charge amounts of the cooling mode and the heating mode can be controlled by the liquid level of the liquid tank 11. When the liquid level in the liquid storage tank 11 reaches a calibrated value, the first drain solenoid valve 33 is closed, and the two-stage compression heating mode shown in fig. 4 is switched.

When the unit is operated in the two-stage compression heating mode shown in fig. 4 and needs to be switched to the refrigeration mode, the intermediate mode of refrigeration is switched according to the heating shown in fig. 6, the liquid-phase refrigerant is output from the liquid storage tank 11 is controlled, the second liquid discharge electromagnetic valve 38 is opened, and the refrigerant with intermediate pressure in the liquid storage tank 11 is discharged into the water side heat exchanger 3 with low pressure, namely, the low pressure side after the EEV40 is refrigerated. After the liquid level in the liquid storage tank 11 is lowered to the calibration position, the mode can be switched to the two-stage compression refrigeration mode as shown in fig. 3.

When in the single-stage compression mode, the first solenoid valve 46 is closed, the oil passage of the high-pressure stage is at the discharge pressure of the low-pressure stage compressor 1, and therefore the high-pressure stage oil separator 9 of the high-pressure stage compressor 2 is at a relatively high pressure, and the first solenoid valve 46 can ensure that the lubricating oil in the high-pressure stage oil separator 9 does not migrate into the low-pressure stage oil separator 8. When the unit is in the two-stage compression refrigeration mode shown in fig. 3 and the two-stage compression heating mode shown in fig. 4, the oil separators of the two-stage compressors are both in operation.

By adopting the design of the first solenoid valve 46, the first check valve 44, the oil pump 16 and the second check valve 45, it is ensured that the oil levels of the oil separators of the two compressors are balanced at any time, regardless of whether any compressor is in a standby state or an operating state, in a complex operating mode such as a single-stage cooling mode, a single-stage heating mode, a two-stage compression cooling mode or a two-stage compression heating mode.

The oil path management module of the system can detect the oil level parameter of the second liquid level sensor 20 of the high-pressure stage compressor 2, the oil level parameter of the first liquid level sensor 21 of the low-pressure stage compressor 1 from time to time, and according to the oil level parameters of the two oil separators, the lubricating oil of the high-pressure stage oil separator 9 can be actively migrated into the low-pressure stage oil separator 8 by controlling the first electromagnetic valve 46. By controlling the oil pump 16, the lubricating oil of the low-pressure-stage oil separator 8 can be actively transferred to the high-pressure-stage oil separator 9, ensuring that the oil levels in the oil separators of both compressors are within a reasonable range.

It is to be understood that the above examples of the present invention are provided for clarity of illustration only and are not limiting of the embodiments of the present invention. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the invention are desired to be protected by the following claims.

Claims (10)

1. A two-stage centrifugal compressor heat pump system, comprising:

A low-pressure stage compressor (1);

a high-pressure stage compressor (2), wherein an air inlet of the high-pressure stage compressor (2) is communicated with an air outlet of the low-pressure stage compressor (1);

a low-pressure-stage oil separator (8), wherein the low-pressure-stage oil separator (8) can supply lubricating oil to the low-pressure-stage compressor (1) and store oil return, and a gas-phase chamber in the low-pressure-stage oil separator (8) is communicated with an air inlet of the low-pressure-stage compressor (1);

the high-pressure-stage oil separator (9) can supply lubricating oil to the high-pressure-stage compressor (2) and store oil return, and a gas phase chamber in the high-pressure-stage oil separator (9) is communicated with an air inlet of the high-pressure-stage compressor (2).

2. The two-stage centrifugal compressor heat pump system according to claim 1, further comprising a first oil passage (22) and a first check valve (44), wherein both ends of the first oil passage (22) are respectively communicated with the oil chamber of the low-pressure stage oil separator (8) and the oil chamber of the high-pressure stage oil separator (9), and the first check valve (44) is arranged on the first oil passage (22) so that the direction of lubricating oil in the first oil passage (22) is from the high-pressure stage oil separator (9) to the low-pressure stage oil separator (8);

And/or, still include second oil circuit (23), oil pump (16) and second check valve (45), the both ends of second oil circuit (23) communicate respectively in the oil pocket of low pressure level oil separator (8) with the oil pocket of high pressure level oil separator (9), oil pump (16) with second check valve (45) set up on second oil circuit (23), so that the trend of lubricating oil in second oil circuit (23) is low pressure level oil separator (8) to high pressure level oil separator (9).

3. A two-stage centrifugal compressor heat pump system according to any one of claims 1-2, further comprising a liquid reservoir (11), the liquid reservoir (11) being capable of releasing refrigerant when the two-stage centrifugal compressor heat pump system is switched to a cooling mode and storing the refrigerant when switched to a heating mode.

4. A two-stage centrifugal compressor heat pump system according to claim 3, further comprising a four-way reversing valve (6), a wind side heat exchanger (4), a water side heat exchanger (3) and an economizer heat exchanger (5), wherein the D port of the four-way reversing valve (6) is selectively communicable with the exhaust port of the low pressure stage compressor (1) and the exhaust port of the high pressure stage compressor (2), wherein the C port of the four-way reversing valve (6) is communicable with one port of the wind side heat exchanger (4), wherein the other port of the wind side heat exchanger (4) is communicable with one port of the first side of the economizer heat exchanger (5), wherein the other port of the first side of the economizer heat exchanger (5) is communicable with one port of the first side of the water side heat exchanger (3), wherein the other port of the first side of the water side heat exchanger (3) is communicable with the E port of the four-way reversing valve (6), and wherein the S port of the four-way reversing valve (6) is communicable with the air inlet of the low pressure stage compressor (1).

5. The two-stage centrifugal compressor heat pump system according to claim 4, wherein one port of the second side of the economizer heat exchanger (5) is selectively communicable with the intake port of the high pressure stage compressor (2).

6. The two-stage centrifugal compressor heat pump system according to claim 4, wherein the inlet of the liquid storage tank (11) is selectively communicated with the other port of the wind side heat exchanger (4), the gas phase chamber of the liquid storage tank (11) is selectively communicated with a communication pipeline between the gas inlet of the high pressure stage compressor (2) and one port of the second side of the economizer heat exchanger (5), and the liquid outlet of the liquid storage tank (11) is selectively communicated with one port of the first side of the water side heat exchanger (3).

7. A two-stage centrifugal compressor heat pump system according to claim 3, further comprising a first liquid level sensor (21), the first liquid level sensor (21) being adapted to measure the liquid level of the low pressure stage oil separator (8);

And/or further comprising a second liquid level sensor (20), the second liquid level sensor (20) being for measuring the liquid level of the high-pressure stage oil separator (9);

and/or, a third level sensor (19) is further included, the third level sensor (19) being for measuring the level of the liquid reservoir (11).

8. The two-stage centrifugal compressor heat pump system according to any one of claims 1-2, further comprising a low pressure stage oil cooler (12), an inlet end of a first side of the low pressure stage oil cooler (12) being in communication with an oil outlet end of the low pressure stage oil separator (8), an outlet end of the first side of the low pressure stage oil cooler (12) being in communication with an oil inlet of a gearbox of the low pressure stage compressor (1);

The high-pressure oil cooler (13) is further included, the inlet end of the first side of the high-pressure oil cooler (13) is communicated with the oil outlet end of the high-pressure oil separator (9), and the outlet end of the first side of the high-pressure oil cooler (13) is communicated with the oil inlet of the gear box of the high-pressure compressor (2).

9. The two-stage centrifugal compressor heat pump system according to claim 8, further comprising a low pressure stage oil filter (14), the low pressure stage oil filter (14) being arranged on a line between an outlet end of a first side of the low pressure stage oil cooler (12) and an oil inlet of a gearbox of the low pressure stage compressor (1);

The high-pressure oil cooler is characterized by further comprising a high-pressure level oil filter (15), wherein the high-pressure level oil filter (15) is arranged on a pipeline between the outlet end of the first side of the high-pressure level oil cooler (13) and the oil inlet of the gear box of the high-pressure level compressor (2).

10. The two-stage centrifugal compressor heat pump system according to claim 9, further comprising a first three-way valve (18), a first end of the first three-way valve (18) being in communication with an oil outlet end of the low pressure stage oil separator (8), a second end of the first three-way valve (18) being in communication with an outlet end of a first side of the low pressure stage oil cooler (12), a third end of the first three-way valve (18) being in communication with an inlet of the low pressure stage oil filter (14);

The high-pressure oil filter further comprises a second three-way valve (17), wherein the first end of the second three-way valve (17) is communicated with the oil outlet end of the high-pressure oil separator (9), the second end of the second three-way valve (17) is communicated with the outlet end of the first side of the high-pressure oil cooler (13), and the third end of the second three-way valve (17) is communicated with the inlet of the high-pressure oil filter (15).