CN114543206A

CN114543206A - Air conditioning system and control method thereof

Info

Publication number: CN114543206A
Application number: CN202011336346.0A
Authority: CN
Inventors: 张薇
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 2020-11-25
Filing date: 2020-11-25
Publication date: 2022-05-27

Abstract

The invention relates to an air conditioning system and a control method thereof. The air conditioning system has an ejector cycle including an ejector that takes a high pressure liquid stream from the condenser and a low pressure steam stream or a low pressure two-phase stream from the evaporator, mixes the high pressure liquid stream and the low pressure steam stream or the low pressure two-phase stream in the ejector into an intermediate pressure two-phase stream and is delivered to a gas-liquid separator, and includes a compressor, a condenser, and an evaporator connected in this order in a loop, wherein the gas-liquid separator delivers the separated gas-phase stream to a bearing of the compressor to lubricate the bearing.

Description

Air conditioning system and control method thereof

Technical Field

The invention relates to the technical field of air conditioners; in particular, the present invention relates to an air conditioning system having an ejector cycle, and further relates to a control method of the air conditioning system.

Background

Air conditioning systems are conventional air conditioning, air quality improving systems in which the bearings of the compressor typically use lubricating oil as a lubricating medium.

Compared with a compressor adopting lubricating oil as a lubricating medium, the oil-free compressor can save a whole set of oil circuit system, save space and save cost. In this case, as an oil-free solution, the bearings of the oil-free compressor have the advantages of an oil-free lubrication system and low maintenance costs. In addition, the gas has smaller viscosity than lubricating oil, is high temperature resistant and has no pollution; at the same time, the use of such bearings is cheaper and has simpler control logic than solutions using magnetic bearings. The lubrication medium for such bearings can be achieved by bleeding air from one or two stages of the compressor, often requiring changes to the compressor design; in addition, bleeding air from the compressor also has the potential to affect the performance of the compressor.

An air conditioning system with ejector cycle is shown in fig. 1. In the illustrated ejector cycle, the ejector 1 obtains a high-pressure liquid flow from the condenser 2 as a working flow, and obtains a low-pressure steam flow or a low-pressure two-phase flow from the evaporator 3 as an injection flow, the two flows are mixed in the ejector 1 and output in the form of a medium-pressure two-phase flow, after being processed by the gas-liquid separator 4, the obtained liquid phase flow returns to the evaporator 3, and the obtained gas phase flow is conveyed to the compressor 5 to be used as a refrigerating medium to directly participate in the refrigeration cycle. In such a system of fig. 1, the provision of an ejector cycle results in a certain pre-pressure of the input of the compressor 5, i.e. the gas phase stream from the gas-liquid separator 4, for advantageously saving the compression work of the compressor. For example, in this example, the compressor may be made to omit one compression stage as compared to a compressor of a conventional air conditioning system. It can be seen that in the air conditioning system of fig. 1, the ejector cycle serves as a work recovery.

Disclosure of Invention

It is an object of one aspect of the present invention to provide an improved air conditioning system.

It is an object of another aspect of the present invention to provide a control method of the air conditioning system of the foregoing aspect.

In order to achieve the foregoing object, an aspect of the present invention provides an air conditioning system having an ejector cycle including an ejector, a compressor, a condenser, and an evaporator connected in series in a circuit, wherein,

the ejector takes a high pressure liquid stream from the condenser and a low pressure steam stream or a low pressure two-phase stream from the evaporator, the high pressure liquid stream and the low pressure steam stream or the low pressure two-phase stream are mixed into an intermediate pressure two-phase stream within the ejector and delivered to a gas-liquid separator, wherein the gas-liquid separator delivers the separated gas-phase stream to bearings of the compressor to lubricate the bearings.

Optionally, in the air conditioning system as described above, the liquid phase stream separated by the gas-liquid separator is sent to a motor of the compressor to cool the motor.

Alternatively, in the air conditioning system as described above, the liquid condensed at the motor is collected at the bottom of the motor and returned to the evaporator, or a part of the liquid phase stream separated by the gas-liquid separator is directly returned to the evaporator.

Optionally, in an air conditioning system as hereinbefore described, the high pressure liquid stream enters the ejector from a working fluid inlet of the ejector and the low pressure steam stream or low pressure two-phase stream enters the ejector from a motive fluid inlet of the ejector.

Optionally, in the air conditioning system as described above, a first throttle valve is provided between the condenser and the working fluid inlet of the ejector, and/or a second throttle valve is provided between the evaporator and the ejector fluid inlet of the ejector.

Optionally, in the air conditioning system as described above, a pressure ratio between the mixing fluid outlet and the ejector fluid inlet of the ejector is between 1 and 2.

Optionally, in the air conditioning system as described above, a pressure ratio between the mixed fluid outlet of the ejector and the ejector fluid inlet is between 1.2 and 1.8.

Alternatively, in the air conditioning system as described above, an air tank is connected between the gas-phase outflow port of the gas-liquid separator and the bearing, the gas-phase flow separated by the gas-liquid separator is stored in the air tank before being supplied to the bearing, and the air tank has a temperature and a pressure controlled so that a phase change does not occur when the gas-phase flow enters the bearing.

Optionally, in an air conditioning system as hereinbefore described, the outlet end of the reservoir is provided with a third throttle to control the flow of gaseous phase supplied to the bearing.

In order to achieve the foregoing object, another aspect of the present invention provides a control method of an air conditioning system as set forth in any of the foregoing aspects, wherein an amount of air supplied to the bearing is controlled by adjusting a flow rate of at least one of:

a high pressure liquid stream taken by the ejector from the condenser;

a low pressure steam stream or a low pressure two-phase stream taken by the ejector from the evaporator; and

a gas phase flow delivered to bearings of the compressor.

Drawings

The disclosure of the present invention will be more apparent with reference to the accompanying drawings. It is to be understood that these drawings are solely for purposes of illustration and are not intended as a definition of the limits of the invention. In the figure:

FIG. 1 is a schematic diagram of a prior art ejector cycle; and

fig. 2 is a schematic diagram of an air conditioning system according to the present invention including an ejector cycle.

Detailed Description

The following describes in detail a specific embodiment of the present invention with reference to the drawings. The following description is merely exemplary of technical aspects of certain embodiments of the present invention, and should not be construed as a complete or restrictive definition of the technical aspects of the present invention.

The terms of orientation of top, bottom, etc. as used in this specification are defined with respect to the orientation as shown in the drawings and these and other terms of orientation should not be construed as limiting terms. Furthermore, the terms "first," "second," "third," and the like are used for descriptive and descriptive purposes only and not for purposes of indicating or implying relative importance between the respective components.

As shown in fig. 2, in this example, the air conditioning system 100 may include a compressor 110, a condenser 120, an expansion valve 130, an evaporator 140, etc. connected in sequence to form a loop, which is used to implement a compression process, a condensation process, an expansion process, and an evaporation process, respectively, so as to perform cooling and air conditioning.

Specifically, when the air conditioning system is in operation, the compressor 110 discharges a high-temperature and high-pressure gas-phase refrigerant, enters the condenser 120 to be condensed into a normal-temperature and high-pressure liquid refrigerant (to dissipate heat), then enters the evaporator 140 through the expansion valve 130, and evaporates (to absorb heat) in the evaporator 140, i.e., to cool. Thereafter, the low-pressure gaseous or two-phase refrigerant resulting from the evaporation returns to the compressor 110 to continue compression and to continue the cycle.

In alternative embodiments, the air conditioning system may omit components in the figure that are not necessary for the refrigeration cycle, or implement each component in a different form, according to different specific needs, or add corresponding components according to specific needs.

An ejector cycle is also provided in the air conditioning system 100, as shown. The ejector cycle may include an ejector 150.

The ejector 150 has a working fluid inlet 151, a motive fluid inlet 152, and a high pressure liquid stream enters the first nozzle of the ejector 150 from the working fluid inlet 151, is converted into a high velocity gas-liquid two-phase stream, and entrains a low pressure vapor stream or a low pressure two-phase stream entering from the motive fluid inlet 152, which enters and mixes in a mixing chamber (not shown), and then passes through a diffusion chamber (not shown) for pressure recovery. At the outlet of the diffusion chamber, i.e., the mixed fluid outlet 153 of the ejector 150, the pressure of the output mixed fluid (medium pressure two-phase fluid) is higher than the pressure of the low pressure steam stream or low pressure two-phase stream upon entering the receiving chamber.

Referring to the illustration, in the ejector cycle, the ejector 150 may take a high pressure liquid stream from the condenser 120 and a low pressure steam stream or a low pressure two-phase stream from the evaporator 140, and the taken high pressure liquid stream and low pressure steam stream or low pressure two-phase stream are mixed into a medium pressure two-phase fluid in the ejector 150 and delivered to the gas-liquid separator 160.

Here, the gas-liquid separator 160 functions to separate the gas and the liquid of the medium-pressure two-phase fluid from the ejector 150. In the illustrated example, the separated vapor phase stream is output from the top of the vapor-liquid separator 160, while the separated liquid phase stream is output from the bottom of the vapor-liquid separator 160. In different embodiments, an appropriate type of gas-liquid separator can be selected according to specific needs, which is not described herein.

According to the illustrated example, the gas-phase stream separated by the gas-liquid separator 160 is delivered to the

bearings

112, 113 of the compressor 110 to serve as a lubricating medium for the bearings. The

bearings

112 and 113 are bearings in which refrigerant gas is used as a lubricant and elastic deformation of the foil thereof is used as a support, and air or the like is used as a lubricant, and in the case of a compressor or the like, a gas phase working medium is used as a lubricant. The bearings do not need external control once the bearings are suspended in use, are free of friction and self-adapting, have much lower friction resistance than oil-lubricated bearings, and are applicable to a wide range of speeds and temperatures.

In conventional applications, such bearings in air conditioning system compressors usually need to be additionally provided with air sources, or bleed air from the compressor, often need additional air pumps and the like, but still have the problems of unstable air source supply, liquid-phase components and the like, so that the performance of the bearings cannot be optimally realized, and the service life of the bearings is even affected. The illustrated embodiment advantageously solves this problem by using an eductor in conjunction with a gas-liquid separator, which advantageously ensures bearing performance, extends bearing life, and improves system operational stability.

According to the illustrated example, the liquid phase separated by the gas-liquid separator 160 is directed to the motor 111 of the compressor 110, serving as a cooling medium for the motor 111 of the compressor 110, providing cooling thereto.

For a conventional compressor motor of an air conditioning system, high-pressure liquid flow is usually directly extracted from a condenser and is injected into a motor cavity through a series of cylindrical pore canals in the circumferential direction and the axial direction of the motor cavity to generate flash evaporation and achieve a cooling effect. In contrast, in the illustrated embodiment, the pressure difference between the condenser and the evaporator is further utilized, and through the ejector and the related components, two objectives can be achieved simultaneously: the bearing cooling device can provide a stable air supply source for the bearing and also can provide a cooling source for cooling the motor. The cooling of the compressor motor in this embodiment can be used as a supplement to its existing cooling or can be used to cool the motor separately.

In other embodiments, the liquid phase stream separated by the gas-liquid separator may also be used as a cooling medium for other components of the air conditioning system, depending on particular needs. In an alternative embodiment, the liquid phase stream separated by the gas-liquid separator may also be returned, in whole or in part, to the evaporator for further circulation.

According to the embodiment as shown in the drawing, the working fluid inlet 151 of the ejector 150 is connected to the outlet of the condenser 120, and a first throttle valve 181 may be disposed between the working fluid inlet 151 of the ejector 150 and the outlet of the condenser 120. The ejector fluid inlet 152 of the ejector 150 is connected to the outlet of the evaporator 140, and a second throttle 182 may be provided between the ejector fluid inlet 152 of the ejector 150 and the outlet of the evaporator 140. The mixed fluid outlet 153 of the ejector 150 is connected to the gas-liquid separator 160. These

throttles

181, 182 may be used to effect flow control and pressure control of the high pressure liquid stream and the low pressure vapor stream or the low pressure two-phase stream introduced into the ejector 150, and thus the intermediate pressure two-phase mixed stream output by the ejector 150.

In alternative embodiments, the first and

second throttles

181, 182 may be replaced with other equivalent means of throttling valves, taking high pressure refrigerant liquid and low pressure refrigerant vapor or low pressure two-phase refrigerant fluid from the condenser 120 and evaporator 140, respectively. In alternative embodiments, alternate forms of the throttling valve include, but are not limited to, an electronic expansion valve, a mechanical valve, and the like.

With reference to fig. 2 and the above description, it can be seen that a high pressure liquid stream enters the ejector 150 from the working fluid inlet 151 of the ejector 150 and a low pressure steam stream or low pressure two-phase stream enters the ejector 150 from the ejector fluid inlet 152 of the ejector 150. As previously described, a first throttling valve 181 between the condenser 120 and the working fluid inlet 151 of the ejector 150 and a second throttling valve 182 between the evaporator 140 and the ejector fluid inlet 152 of the ejector 150 may be used to control and regulate the flow of high pressure liquid from the condenser 120 and the flow of low pressure steam or low pressure two-phase flow from the evaporator 140, respectively.

After being mixed by the ejector 150, the intermediate-pressure two-phase fluid is ejected from the mixed fluid outlet 153 of the ejector 150. The pressure ratio between the mixed fluid outlet 153 and the ejector fluid inlet 152 of the ejector 150 may be between 1 and 2. In alternative embodiments, the pressure ratio between the mixed fluid outlet 153 and the ejector fluid inlet 152 of the ejector 150 may be between 1.2 and 1.8. The provision of the above pressure ratio can contribute to spraying the liquid phase stream separated by the gas-liquid separator 160 into the motor cavity to exert a cooling effect, preventing the cooling effect from being impaired due to pressure loss. When the motor is cooled, liquid phase flow injected into the motor cavity is subjected to flash evaporation and is quickly gasified to absorb heat, so that a good cooling effect is achieved.

As described above, the intermediate-pressure two-phase fluid mixed by the ejector 150 is sent to the gas-liquid separator 160, where the intermediate-pressure two-phase fluid is separated into a gas-phase flow and a liquid-phase flow at the gas-liquid separator 160. The gas-liquid separator 160 has a gas-phase outflow port and a liquid-phase outflow port; the illustrated example has a gas phase stream outlet and a liquid phase stream outlet at the top and bottom of the gas-liquid separator 160, respectively.

In this example, the gas tank 170 may be connected to the gas phase outflow port, and the gas tank 170 is communicated to the

bearings

112, 113 of the compressor 110 via the third throttle valve 183, so that the gas phase flow separated by the gas-liquid separator 160 may be used as a lubricating medium for the

bearings

112, 113, and an oil-free solution for compressor bearing lubrication may be achieved. The maintenance cost of this oil-free solution is low; compared with a magnetic suspension bearing, the cost is lower.

In addition, the gas supply source stabilization achieved by the gas tank 170 does not require an additional pump, which is crucial to the performance of the bearing.

In alternative embodiments, the gas-phase stream separated by the gas-liquid separator 160 may be used for purposes other than lubricating the medium, as desired. For example, a portion of the vapor phase stream separated by the vapor-liquid separator 160 may also be returned to the inlet of the compressor 110 for the purpose of saving a portion of the compression work.

The illustrated embodiment provides both the lubrication medium supply of the

bearings

112, 113 of the compressor 110 and the cooling medium supply of the motor 111 of the compressor 110 using ejector circulation without changing the existing compressor design, without losing compressor work, with little change to the existing technology when applied, and thus is easy to implement.

It can be seen that according to the illustrated embodiment, the gas phase separated by the gas-liquid separator 160 may be used as a lubrication medium for the

bearings

112, 113 of the compressor 110. The gas phase outlet of the gas-liquid separator 160 may be connected to a gas tank 170, and the separated gas phase may be stored in the gas tank 170 before being used for the

bearings

112, 113. The gas reservoir 170 may also have a controlled temperature and pressure so that a phase change does not occur as the gas phase flows into the

bearings

112, 113. A third throttle valve 183 provided at the outlet end of the gas reservoir 170 may be used to control the gas phase supplied to the bearings 112,113. In various embodiments, the air reservoir 170 and/or the third throttle 183 downstream thereof may be omitted, as the case may be.

In alternative embodiments the third throttle valve 183 may be replaced by other equivalent means of a throttle valve. In alternative embodiments, alternate forms of the throttling valve include, but are not limited to, an electronic expansion valve, a mechanical valve, and the like.

Further, as can be seen from fig. 2, below the compressor 110 there is provided a collecting device, for example a collecting bottom shell, which on the one hand can act as a housing to prevent the ingress of impurities and on the other hand can also collect and store the liquid resulting from condensation, dissipate part of the heat, etc. The collecting device may be connected to the evaporator. By means of the collecting device, the liquid resulting from the condensation of the steam at its motor 111 can be stored at the bottom of the motor and returned to the evaporator. In fig. 2, a circuit for returning liquid to the evaporator is shown, which returns to the refrigerant inlet of the evaporator 140 or flows into the evaporator 140 through a separate channel.

In addition, another aspect of the present invention also provides a control method of the air conditioning system according to any one of the foregoing embodiments. In the method, the amount of air supplied to the bearing may be controlled by adjusting the flow rate of at least one of the following streams: a high pressure liquid stream drawn from the condenser by an ejector; a low pressure vapor stream or a low pressure two-phase stream taken from the evaporator by the ejector; and a gas phase stream delivered to the bearings of the compressor. By means of this control method, with the air conditioning system of the aforementioned embodiments, at least the supply of air to the compressor bearings can be advantageously achieved to adapt it to the specific operating situation.

The technical scope of the present invention is not limited to the above description, and those skilled in the art can make various modifications, adaptations or combinations of the above embodiments without departing from the technical spirit of the present invention, and the modifications, adaptations or combinations should fall within the scope of the present invention.

List of reference numerals

1 ejector

2 condenser

3 evaporator

4 gas-liquid separator

5 compressor

100 air conditioning system

110 compressor

111 electric machine

112. 113 bearing

120 condenser

130 expansion valve

140 evaporator

150 ejector

151 working fluid inlet

152 ejector fluid inlet

153 mixed fluid outlet

160 gas-liquid separator

170 gas storage tank

181 first throttle valve

182 second throttle valve

183 third throttle valve

Claims

1. An air conditioning system having an ejector cycle comprising an ejector, wherein,

2. The air conditioning system of claim 1, wherein the liquid phase stream separated by the gas-liquid separator is delivered to a motor of the compressor to cool the motor.

3. The air conditioning system of claim 2, wherein liquid condensed at the motor is collected at the bottom of the motor and returned to the evaporator, or a portion of the liquid phase stream separated by the gas-liquid separator is returned directly to the evaporator.

4. The air conditioning system of claim 1, wherein the high pressure liquid stream enters the ejector from a working fluid inlet of the ejector and the low pressure steam stream or low pressure two-phase stream enters the ejector from a motive fluid inlet of the ejector.

5. An air conditioning system as claimed in claim 4, wherein a first throttle valve is provided between the condenser and the working fluid inlet of the ejector and/or a second throttle valve is provided between the evaporator and the ejector fluid inlet of the ejector.

6. The air conditioning system of claim 5, wherein the ejector has a pressure ratio between the mixing fluid outlet and the ejector fluid inlet of between 1 and 2.

7. The air conditioning system of claim 6, wherein a pressure ratio between the mixed fluid outlet of the ejector and the ejector fluid inlet is between 1.2 and 1.8.

8. The air conditioning system as claimed in claim 1, wherein an air tank is connected between a gas phase outflow port of the gas-liquid separator and the bearing, the gas phase flow separated by the gas-liquid separator is stored in the air tank before being supplied to the bearing, and the air tank has a temperature and pressure controlled so that a phase change does not occur when the gas phase flow enters the bearing.

9. The air conditioning system of claim 8, wherein an outlet end of the air reservoir is provided with a third throttle valve to control the flow of gas phase supplied to the bearing.

10. A control method of an air conditioning system as claimed in any one of the preceding claims 1 to 9, wherein the amount of air supplied to the bearing is controlled by adjusting the flow rate of at least one of the following streams:

a high pressure liquid stream taken by the ejector from the condenser;

a gas phase flow delivered to bearings of the compressor.