CN115183487A - High-speed rail trans-critical carbon dioxide heat pump air conditioning system and control method thereof - Google Patents
High-speed rail trans-critical carbon dioxide heat pump air conditioning system and control method thereof Download PDFInfo
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- CN115183487A CN115183487A CN202210785086.8A CN202210785086A CN115183487A CN 115183487 A CN115183487 A CN 115183487A CN 202210785086 A CN202210785086 A CN 202210785086A CN 115183487 A CN115183487 A CN 115183487A
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- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 title claims abstract description 68
- 238000000034 method Methods 0.000 title claims abstract description 46
- 229910002092 carbon dioxide Inorganic materials 0.000 title claims abstract description 34
- 239000001569 carbon dioxide Substances 0.000 title claims abstract description 34
- 238000004378 air conditioning Methods 0.000 title claims abstract description 30
- 238000010438 heat treatment Methods 0.000 claims abstract description 31
- 239000003507 refrigerant Substances 0.000 claims abstract description 25
- 239000007788 liquid Substances 0.000 claims description 15
- 238000005057 refrigeration Methods 0.000 claims description 12
- 238000001816 cooling Methods 0.000 claims description 8
- 238000012544 monitoring process Methods 0.000 claims description 3
- 238000004364 calculation method Methods 0.000 claims description 2
- 230000009286 beneficial effect Effects 0.000 abstract description 5
- 238000010792 warming Methods 0.000 abstract description 5
- 238000004134 energy conservation Methods 0.000 abstract description 4
- 230000009467 reduction Effects 0.000 abstract description 4
- 230000008859 change Effects 0.000 description 5
- 238000005265 energy consumption Methods 0.000 description 4
- 238000002474 experimental method Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 238000011161 development Methods 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 238000005314 correlation function Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 231100000956 nontoxicity Toxicity 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
- F25B9/002—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant
- F25B9/008—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant the refrigerant being carbon dioxide
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B61—RAILWAYS
- B61D—BODY DETAILS OR KINDS OF RAILWAY VEHICLES
- B61D27/00—Heating, cooling, ventilating, or air-conditioning
- B61D27/0018—Air-conditioning means, i.e. combining at least two of the following ways of treating or supplying air, namely heating, cooling or ventilating
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B49/00—Arrangement or mounting of control or safety devices
- F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2309/00—Gas cycle refrigeration machines
- F25B2309/06—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T30/00—Transportation of goods or passengers via railways, e.g. energy recovery or reducing air resistance
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- Mechanical Engineering (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
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- Chemical Kinetics & Catalysis (AREA)
- Air Conditioning Control Device (AREA)
Abstract
The invention discloses a high-speed rail trans-critical carbon dioxide heat pump air conditioning system and a control method thereof, wherein the control method comprises the following steps: acquiring the temperature of a carriage, the outdoor environment temperature of an area where a train passes, a fresh air ratio, the passenger carrying rate of the carriage, the running speed of the train, the current system exhaust pressure and the valve opening of a current system electronic expansion valve; selecting the number of running compressors; calculating the running frequency of the compressor; calculating the optimal exhaust pressure of the system; adjusting the valve opening of the electronic expansion valve to achieve the optimal pressure discharge pressure of the system; wherein carbon dioxide is used as the circulating refrigerant. The invention adopts carbon dioxide as the refrigerant, has low global warming potential GWP and good heating performance, and is beneficial to energy conservation and emission reduction of high-speed rails.
Description
Technical Field
The invention belongs to the technical field of high-speed rail heat pump air conditioner control, and particularly relates to a high-speed rail transcritical carbon dioxide heat pump air conditioner system and a control method thereof.
Background
High-iron refrigerant from traditional HFCs to CO 2 Waiting for the natural refrigerant to replace will speed up; among them, conventional hydrofluorocarbon HFCs refrigerant has high global warming potential GWP and poor low-temperature heating performance, and CO 2 As a natural refrigerant, the refrigerant has the advantages of low GWP, good heating performance, incombustibility, no toxicity, reliability and the like, and is an ideal refrigerant substitute scheme. Due to CO 2 The refrigerant and the transcritical air-conditioning heat pump system thereof have been popularized to the application field of railway vehicles in recent years, so that a new control method for the heat pump air-conditioning of the railway vehicles is necessary to be provided for the transcritical CO 2 A heat pump air conditioner.
The existing high-speed rail air conditioning system generally adopts a dual-system operation mode, and the refrigerating capacity is adjusted by 0 percent, 50 percent and 100 percent through the start-stop control of a dual-system compressor; in addition, since the conventional refrigerant has poor low-temperature heating performance, an electric heater is also required to keep heating sufficient. The control mode has certain defects, mainly including: the energy consumption is larger due to less refrigerating capacity adjusting stages; the high-speed rail has wide operation region and large external environment change, the carriage heat load change is large, a single refrigerating capacity adjusting mode cannot adapt to the change of the heat load, and the refrigerating capacity is usually large; in addition, transcritical CO 2 The circulation system often has an optimal exhaust pressure at which the system energy efficiency ratio COP is highest and the system energy consumption is lowest, so that it is necessary to control the system to operate at the optimal exhaust pressure and control the valve opening of the electronic expansion valve to achieve the optimal exhaust pressure.
Transcritical CO of existing other vehicles (e.g., passenger cars and buses) 2 The system-related control method is not applicable to high-speed rail, mainly because: in terms of system configuration structure, the high-speed rail air conditioner is generally a double system, and the passenger car are generally a single system; the high-speed rail has high running speed, large geographical span and large running condition change, and the passenger car have small running condition change; in addition, the high-speed rail outdoor fan has compact structure, so that the heat exchange temperature difference is large, and the air pressure loss is large due to the long indoor air duct. Therefore, a new set of trans-critical CO suitable for high-speed rail needs to be proposed 2 And (4) a control idea of the system.
Disclosure of Invention
The invention aims to provide a high-speed rail trans-critical carbon dioxide heat pump air conditioning system and a control method thereof, so as to solve one or more technical problems. The invention adopts carbon dioxide as the refrigerant, has low global warming potential GWP and good heating performance, and is beneficial to energy conservation and emission reduction of high-speed rails.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a high-speed rail transcritical carbon dioxide heat pump air conditioning system, which comprises: the indoor fan and the fresh air valve are used by two identical units and the two units together;
each of the two units comprises a compressor, a first electric three-way ball valve, a second electric three-way ball valve, an electronic expansion valve, an in-vehicle heat exchanger, an out-vehicle heat exchanger, a heat regenerator, a gas-liquid separator and an outdoor fan; the outlet of the compressor is communicated with the port b of the first electric three-way ball valve, and the port a of the first electric three-way ball valve is communicated with the port c of the first electric three-way ball valve through the first channel of the heat exchanger outside the vehicle, the first channel of the heat regenerator, the electronic expansion valve and the first channel of the heat exchanger inside the vehicle at one time; an inlet of the compressor is communicated with an e port of the second electric three-way ball valve through a second channel of the heat regenerator and the gas-liquid separator in sequence, a d port of the second electric three-way ball valve is communicated with an inlet of a first channel of the heat exchanger outside the vehicle, and an f port of the second electric three-way ball valve is communicated with an outlet of the first channel of the heat exchanger inside the vehicle; the heat exchanger outside the vehicle is provided with the outdoor fan; the heat exchanger in the vehicle is provided with the indoor fan and a fresh air valve; the circulating refrigerant being CO 2 。
A further development of the invention is that the compressor is an inverter compressor.
The invention provides a control method of a high-speed rail trans-critical carbon dioxide heat pump air conditioning system, which comprises the following steps:
in the cooling mode of operation, CO 2 The refrigerant flows from the port b of the first electric three-way valve to the port a and reaches the heat exchanger outside the vehicle, and flows from the port f of the second electric three-way valve to the port e and reaches the gas-liquid separator; in heating mode of operation, CO 2 The refrigerant flows from the port b of the first electric three-way valve to the port c to reach the heat exchanger in the vehicle, and flows from the port d of the first electric three-way valve to the port e to reach the gas-liquid separator;
obtaining the temperature T of the carriage i And the ambient temperature T outside the vehicle o Fresh air ratio R fresh Carriage passenger carrying rate W pass Vehicle running speed V S Current system exhaust pressure P n And a valve opening OP of the electronic expansion valve of the current system; based on the temperature T of the carriage i Selecting the number of running compressors according to the target compartment temperature; according to the temperature T of the carriage i Ambient temperature T o Fresh air ratio R fresh Carriage passenger carrying rate W pass And a vehicle running speed V s Determining the running frequency of the compressor; according to the temperature T of the carriage i External environment temperature T o Fresh air ratio R fresh Calculating the optimal exhaust pressure of the system according to the frequency of the compressor; and based on the optimal exhaust pressure of the system, adjusting the valve opening of the electronic expansion valve to achieve the optimal exhaust pressure of the system to realize control.
In a further development of the control method according to the invention, the control is based on the cabin temperature T i The step of selecting the number of compressors to operate in relation to the target compartment temperature includes:
setting the target compartment temperature to T in the cooling operation mode cs ，T c1 Is the upper limit value, T, of the temperature fluctuation of the carriage during refrigeration c4 Is the lower limit value, T, of the temperature fluctuation of the carriage during refrigeration cs ＝1/2*(T c1 +T c4 ) Several temperature limit values for switching the control state are respectively T c1 、 T c2 、T c3 、T c4 ，T c1 ＞T c2 ＞T c3 ＞T c4 And | T c1 -T c2 |:|T c2 -T c3 |:|T c3 -T c4 |＝a 1 :a 2 :a 3 ，a 1 ＞a 2 ＞a 3 (ii) a When the temperature T of the compartment i ＞T c1 Two compressors are started in time, the frequency is operated in a higher frequency state, T c2 ＜T i ≤T c1 Two compressors are started in time, the frequency is operated in a medium frequency state, T c3 ＜T i ≤T c2 Two compressors are started in time, and the frequency is operated in a lower frequency state T c4 ＜T i ≤T c3 A compressor is started, the frequency is operated in a lower frequency state, T i ≤T c4 When the compressor is shut down and until T i ＞T c1 Starting up the computer;
in the heating operation mode, the target cabin temperature is set to T hs ，T h1 Is the upper limit value, T, of the temperature fluctuation of the compartment during heating h4 Is the lower limit value of the temperature fluctuation of the compartment during heating, T hs ＝1/2*(T h1 +T h4 ) Several temperature limit values for switching the control state are respectively T h1 、 T h2 、T h3 、T h4 ，T h1 ＜T h2 ＜T h3 ＜T h4 And | T h1 -T h2 |:|T h2 -T h3 |:|T h3 -T h4 |＝b 1 :b 2 :b 3 ，b 1 ＞b 2 ＞b 3 When the temperature T of the compartment i ＜T h1 Two compressors are started in time, the frequency is operated in a higher frequency state, T h1 ≤T i ＜T h2 Two compressors are started in time, the frequency is operated in a medium frequency state, T h2 ≤T i ＜T h3 Two compressors are started in time, the frequency is operated in a lower frequency state, T h3 ≤T i ＜T h4 A compressor is started, the frequency is operated in a lower frequency state, T i ≥T h4 When the compressor is shut down and up to T i ＜T h1 And starting up the computer.
The control method of the invention is further improved in that the control method is based on the temperature T of the compartment i External environment temperature T o Fresh air ratio R fresh Carriage passenger carrying rate W pass And a vehicle running speed V s The step of determining the operating frequency of the compressor comprises:
in the cooling operation mode, the ambient temperature T outside the vehicle is adjusted oc As a dividing line, the ambient temperature T outside the vehicle o Higher than T oc The total compressor frequency is higher than the ambient temperature T outside the vehicle o Below T oc Overall compressor frequency of time; frequency f cool The control is performed according to the following correlation:
when T is o ≥T oc When f is present cool ＝f1(T o ，T i ，R fresh ，W pass ，V s )；
When T is o ＜T oc When f is turned on cool ＝f2(T o ，T i ，R fresh ，W pass ，V s )；
In the heating operation mode, the ambient temperature T outside the vehicle is adjusted oh As a dividing line, the ambient temperature T outside the vehicle o Below T oh Total compressor frequency above ambient outside temperature T o Higher than T oh Overall compressor frequency of time; frequency f heat The control is performed according to the following correlation:
when T is o ≤T oh When f is present heat ＝f3(T o ，T i ，R fresh ，W pass ，V s )；
When T is o ＞T oh When f is turned on heat ＝f4(T o ，T i ，R fresh ，W pass ，V s )。
The control method of the invention is further improved in that the control method is based on the temperature T of the compartment i External environment temperature T o Fresh air ratio R fresh The step of calculating the optimal exhaust pressure of the system with the frequency of the compressor comprises the following steps:
according to the temperature T of the carriage i External environment temperature T o Fresh air ratio R fresh Calculating the optimal exhaust pressure p of the system with the frequency of the compressor op (ii) a Wherein the optimal refrigerating discharge pressure is p op，cool Heating optimum discharge pressure p op，heat The optimum exhaust pressure is calculated according to the following correlation: p is a radical of formula op，cool ＝fc(T o ，T i ，R fresh ，f cool )；p op，heat ＝fh(T o ，T i ，R fresh ，f cool )。
The control method of the invention is further improved in that if the calculated system optimum exhaust pressure value is greater than 13MPa, the system optimum exhaust pressure is set to 13MPa.
The control method is further improved in that the step of adjusting the valve opening of the electronic expansion valve based on the system optimal exhaust pressure to achieve the system optimal exhaust pressure to realize control comprises the following steps:
pressure discharge value p of monitoring system n If the difference value is equal to the set pressure value p op，cool Or p op，heat The valve opening degree of the electronic expansion valve is unchanged when the absolute value is less than 0.05MPa, the valve opening degree of the electronic expansion valve is reduced when the absolute value is greater than the set discharge pressure value by 0.05MPa, the valve opening degree of the electronic expansion valve is increased when the absolute value is less than the set discharge pressure value by 0.05MPa, and the differential pressure is converted into a valve opening degree variation delta OP = C | p when the electronic expansion valve is adjusted n -p op And | C is a proportionality coefficient.
Compared with the prior art, the invention has the following beneficial effects:
in the present invention, a suitable transcritical CO is provided 2 A compressor frequency and system optimal exhaust pressure control method of a high-speed rail heat pump air conditioner is disclosed. Compared with the traditional hydrofluorocarbon HFCs refrigerant carbon dioxide refrigerant, the refrigerant is environment-friendly and clean, has low Global Warming Potential (GWP) and good heating performance, and is beneficial to energy conservation and emission reduction of high-speed rails.
The control method can control the number of the running compressors and realize the multi-stage adjustment of energy; the running frequency of the compressor can be selected, and optimal energy distribution is realized to ensure the comfort of the carriage; the system energy efficiency is saved by searching the optimal exhaust pressure of the system and adjusting the opening of the expansion valve.
According to the invention, the temperature range of the carriage is divided into a plurality of small intervals and multi-stage control, each stage corresponds to different refrigerating capacity ranges, the temperature fluctuation range is narrowed, and the compressor is protected from being started and stopped frequently.
In the invention, the correlation of the compressor frequency is provided aiming at different external environment temperatures and compartment temperatures.
In the present invention, trans-critical CO 2 The system has the lowest energy consumption under the optimal exhaust pressure, and also provides a correlation of the optimal exhaust pressure and a control method of the valve opening of the electronic expansion valve due to the fact that the correlation of the optimal exhaust pressure with the ambient temperature, the fresh air ratio and the compartment temperature is high.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art are briefly introduced below; it is obvious that the drawings in the following description are some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.
Fig. 1 is a schematic structural diagram of a high-speed rail transcritical carbon dioxide heat pump air conditioning system according to an embodiment of the present invention;
fig. 2 is a schematic flow chart of a control method of a high-speed rail transcritical carbon dioxide heat pump air conditioning system according to an embodiment of the present invention;
FIG. 3 is a schematic diagram illustrating a flow of determining the number of compressors of the transcritical carbon dioxide high-speed rail heat pump air conditioning system according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of the frequency determination process of the transcritical carbon dioxide high-speed rail heat pump air conditioning system in the embodiment of the invention;
FIG. 5 is a schematic flow chart of an optimal exhaust pressure control method of a transcritical carbon dioxide high-speed rail heat pump air conditioning system according to an embodiment of the present invention;
in the figure, 1, a compressor; 2. a first electric three-way ball valve; 3. a second electric three-way ball valve; 4. an electronic expansion valve; 5. a heat exchanger inside the vehicle; 6. an exterior heat exchanger; 7. a heat regenerator; 8. a gas-liquid separator; 9. an outdoor fan; 10. an indoor fan; 11. a fresh air valve; 12. an indoor heat exchanger; 13. the rest of the components.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
The invention is described in further detail below with reference to the accompanying drawings:
referring to fig. 1, a high-speed rail transcritical carbon dioxide heat pump air conditioning system according to an embodiment of the present invention includes two units with identical components; each unit comprises a compressor 1, a first electric three-way ball valve 2, a second electric three-way ball valve 3, an electronic expansion valve 4, an in-vehicle heat exchanger 5, an out-vehicle heat exchanger 6, a heat regenerator 7, a gas-liquid separator 8 and an outdoor fan 9, the two units share two indoor fans 10 and a fresh air valve 11, and for simplification, the second unit is exemplarily expressed as comprising an indoor heat exchanger 12 and other parts 13 except the indoor heat exchanger 12.
In the embodiment of the invention, the outlet of a compressor 1 is connected with the port b of a first electric three-way ball valve 2, the port a of the first electric three-way ball valve 2 is connected with the inlet of an external heat exchanger 6 of a vehicle, the port c is connected with the outlet of an internal heat exchanger 5 of the vehicle, the outlet of the external heat exchanger 6 of the vehicle is connected with the first inlet of a heat regenerator 7, the first outlet of the heat regenerator 7 is connected with the inlet of an electronic expansion valve 4, the outlet of the electronic expansion valve 4 is connected with the inlet of the internal heat exchanger 5 of the vehicle, the outlet of the internal heat exchanger 5 of the vehicle is connected with the port f of a second electric three-way ball valve 3, the port e of the second electric three-way ball valve 3 is connected with the inlet of a gas-liquid separator 8, the port d is connected with the inlet of the external heat exchanger 6 of the vehicle, the outlet of the gas-liquid separator 8 is connected with the second inlet of the heat regenerator 7, and the second outlet of the heat regenerator 7 is connected with the inlet of a variable frequency compressor 1.
The main working modes of the system provided by the embodiment of the invention are a refrigeration mode and a heating mode, and the system realizes the conversion between the refrigeration mode and the heating mode through two electric three-way valves; in the refrigeration mode, the refrigerant carbon dioxide flows from the port b of the first electric three-way valve to the port a to reach the heat exchanger outside the vehicle, and flows from the port f of the second electric three-way valve to the port e to reach the gas-liquid separator; in the heating mode, the refrigerant carbon dioxide flows from the b port to the c port of the first electric three-way valve to the vehicle interior heat exchanger, and flows from the d port to the e port of the first electric three-way valve to the gas-liquid separator.
In the embodiment of the invention, the system compressor is preferably a variable frequency compressor, so that the system can realize the energy adjustment of the refrigerating capacity and the heating capacity, and the two units adjust the frequency by using the same compressor control method, namely the compressor frequency is kept the same and the two units work simultaneously.
Referring to fig. 2, a control method of a high-speed rail transcritical carbon dioxide heat pump air conditioning system according to an embodiment of the present invention includes the steps of:
s1, collecting compartment temperature T i Collecting outdoor ambient temperature T of area where train passes o Collecting fresh air valve opening, i.e. collecting fresh air ratio R fresh (ii) a Collecting carriage passenger carrying rate W pass And collecting the running speed V of the vehicle S Collecting the current system exhaust pressure P n Collecting the valve opening OP of the electronic expansion valve of the current system;
s2, selecting the number of running compressors;
s3, calculating the running frequency of the compressor;
s4, calculating the optimal exhaust pressure of the system; adjusting the valve opening of the electronic expansion valve to achieve the optimal pressure discharge pressure of the system;
specifically, the above steps are all performed dynamically in real time to achieve dynamic adjustment of the system.
Referring to fig. 3, a method for selecting the number of operating compressors for a high-speed rail transcritical carbon dioxide heat pump air conditioning system according to an embodiment of the present invention includes the following steps:
setting the target compartment temperature to T in the cooling operation mode cs ，T c1 Is the upper limit value, T, of the temperature fluctuation of the carriage during refrigeration c4 Is the lower limit value, T, of the temperature fluctuation of the carriage during refrigeration cs ＝1/2*(T c1 +T c4 ) Several temperature limit values for switching the control state are respectively T c1 、 T c2 、T c3 、T c4 ，T c1 ＞T c2 ＞T c3 ＞T c4 And | T c1 -T c2 |:|T c2 -T c3 |:|T c3 -T c4 |＝a 1 :a 2 :a 3 ，a 1 ＞a 2 ＞a 3 When the temperature T of the compartment i ＞T c1 Two compressors are started in time, the frequency is operated in a higher frequency state, T c2 ＜T i ≤T c1 Two compressors are started, the frequency is operated in a medium frequency state, T c3 ＜T i ≤T c2 Two compressors are started in time, and the frequency is operated in a lower frequency state T c4 ＜T i ≤T c3 A compressor is started, the frequency is operated in a lower frequency state, T i ≤T c4 When the compressor is shut down until T i ＞T c1 Starting up the computer;
in the heating operation mode, the target compartment temperature is set to T hs ，T h1 Is the upper limit value, T, of the temperature fluctuation of the compartment during heating h4 Is the lower limit value of the temperature fluctuation of the compartment during heating, T hs ＝1/2*(T h1 +T h4 ) Several temperature limit values for switching the control state are respectively T h1 、 T h2 、T h3 、T h4 ，T h1 ＜T h2 ＜T h3 ＜T h4 And | T h1 -T h2 |:|T h2 -T h3 |:|T h3 -T h4 |＝b 1 :b 2 :b 3 ，b 1 ＞b 2 ＞b 3 When the temperature T of the compartment i ＜T h1 Two compressors are started in time, the frequency is operated in a higher frequency state, T h1 ≤T i ＜T h2 Two compressors are started, the frequency is operated in a medium frequency state, T h2 ≤T i ＜T h3 Two compressors are started in time, the frequency is operated in a lower frequency state, T h3 ≤T i ＜T h4 A compressor is started, the frequency is operated in a lower frequency state, T i ≥T h4 The compressor is shut down until T i ＜T h1 And starting up the computer.
Exemplary of embodiments of the invention a 1 、a 2 、a 3 And b 1 、b 2 、b 3 Temperature T of carriage i And the outdoor ambient temperature T o The degree of correlation is high, and a is changed under a certain environment temperature and a set compartment temperature 1 :a 2 And a 2 :a 3 Through experiments or simulation, the optimization targets are that the number of start-stop times of the compressor in unit time is less and the temperature fluctuation amplitude is small, and if the number of start-stop times of the compressor in unit time is least and the temperature fluctuation amplitude is small, the corresponding a is taken 1 :a 2 And a 2 :a 3 And, in addition, a in which different ambient temperatures correspond to the temperature of the vehicle compartment 1 :a 2 And a 2 :a 3 Different value of a 1 :a 2 ＝f1(T o ，T i )，a 2 :a 3 ＝f2(T o ，T i ) The corresponding correlation function relationship can be obtained through limited experiments or simulations.
Referring to fig. 4, a method for calculating an operating frequency of a compressor in a high-speed rail transcritical carbon dioxide heat pump air conditioning system according to an embodiment of the present invention includes the following steps:
the performance of the system is reduced when the outdoor environment temperature is increased in the refrigeration operation mode, and the outdoor environment temperature T is adjusted to meet the refrigeration capacity oc As a dividing line, ambient temperature T o Higher than T oc Total compressor frequency above ambient temperatureT o Lower than T oc Overall compressor frequency of time, and thus the cooling mode frequency f cool The control is performed according to the following correlation:
when T is o ≥T oc When f is present cool ＝f1(T o ，T i ，R fresh ，W pass ，V s )；
When T is o ＜T oc When f is present cool ＝f2(T o ，T i ，R fresh ，W pass ，V s )；
Reducing the outdoor environment temperature in the heating operation mode to reduce the system performance, and setting the environment temperature T to meet the heating quantity oh As a dividing line, the ambient temperature is lower than T oh Total compressor frequency above ambient temperature above T oh Overall compressor frequency of time, thus heating operation mode frequency f heat The following correlation is used for control:
when T is o ≤T oh When f is present heat ＝f3(T o ，T i ，R fresh ，W pass ，V s )；
When T is o ＞T oh When f is present heat ＝f4(T o ，T i ，R fresh ，W pass ，V s )；
The specific control relation is obtained by limited experiments according to the function according to the quantitative relation.
Principle explanatory, car load and ambient temperature T o There is an important relationship that the load directly influenced by the ambient temperature includes the fresh air load and the enclosure load, so the compressor frequency is not only related to the compartment temperature T i In relation to the above, different compressor frequencies should be adopted at different environmental temperatures, and in addition, the fresh air load and the personnel load are larger, so that the fresh air ratio R is larger fresh Carriage passenger carrying rate W pass Also has a great influence on the load, and finally the vehicle running speed V s The heat transfer coefficient of the car body is influenced, and the load is also greatly influenced. In conclusion, the pressure is determined according to the temperature of the carriage, the ambient temperature outside the vehicle, the fresh air ratio, the passenger carrying rate of the carriage and the running speed of the vehicleThe compressor operating frequency.
Referring to fig. 5, the method for calculating the optimal exhaust pressure of the system according to the embodiment of the present invention specifically includes the following steps: calculating the optimal exhaust pressure p of the system according to the temperature of the carriage, the temperature of the environment outside the vehicle, the fresh air ratio and the frequency of the compressor op The optimal refrigerating discharge pressure is p op，cool Heating optimum discharge pressure p op，heat The optimum exhaust pressure is calculated according to the following correlation:
p op，cool ＝fc(T o ，T i ，R fresh ，f cool )；
p op，heat ＝fh(T o ，T i ，R fresh ，f cool )；
the specific control relation is obtained through limited experiments according to the functions according to the quantitative relation;
considering the system safety, the system exhaust pressure cannot be greater than 13MPa, and if the calculated optimal exhaust pressure value is greater than 13MPa, the exhaust pressure will be set to 13MPa.
In the embodiment of the invention, the method for adjusting the opening degree of the electronic expansion valve comprises the following steps: pressure discharge value p of monitoring system n If the difference value p is equal to the set pressure value op，cool Or p op，heat The valve opening of the electronic expansion valve is unchanged when the absolute value is less than 0.05MPa, the valve opening of the electronic expansion valve is decreased when the absolute value is greater than the set discharge pressure value by 0.05MPa, the valve opening of the electronic expansion valve is increased when the absolute value is less than the set discharge pressure value by 0.05MPa, and the differential pressure is converted into a valve opening variation quantity delta OP = C | p when the electronic expansion valve is adjusted n -p op And C is a proportional coefficient, when the difference between the current exhaust pressure and the optimal exhaust pressure is large, the valve opening variation of the electronic expansion valve is large, and when the difference between the current exhaust pressure and the optimal exhaust pressure is small, the valve opening variation of the electronic expansion valve is small.
To sum up, the embodiment of the invention discloses a high-speed rail transcritical carbon dioxide heat pump air conditioning system and a control method thereofThe air-liquid separator, the outdoor fan, the indoor fan and the fresh air valve; the temperature range of the carriage is divided into a plurality of intervals and multi-stage control, each stage corresponds to different refrigerating capacity ranges, the temperature fluctuation range is reduced, and the compressor is protected; meanwhile, aiming at different external environment temperatures, carriage temperatures and other influence parameters, a compressor frequency correlation is provided to ensure the normal operation of the high-speed rail air-conditioning heat pump in a wide working condition range, an optimal exhaust pressure correlation of the high-speed rail air-conditioning system is provided, signals of the environment temperature, the carriage temperature, the fresh air ratio and the like are collected, the optimal exhaust pressure is obtained through calculation, the optimal performance of the transcritical carbon dioxide system is achieved, and the control method of the electronic expansion valve is provided. The control method of the high-speed rail transcritical carbon dioxide heat pump air conditioning system provided by the embodiment of the invention is used for controlling the number of running compressors, realizing energy multi-stage regulation, selecting the running frequency of the compressors, realizing energy optimal distribution to ensure the comfort level of a carriage, searching the optimal exhaust pressure of the system and regulating the opening of an expansion valve, and saving the energy efficiency of the system. Compared with the traditional hydrofluorocarbon HFCs refrigerant carbon dioxide refrigerant, the refrigerant is environment-friendly and clean, has low Global Warming Potential (GWP) and good heating performance, and is beneficial to energy conservation and emission reduction of high-speed rails. The temperature range of the carriage is divided into a plurality of sections and multi-stage control, each stage corresponds to different refrigeration capacity ranges, the temperature fluctuation range is reduced, and the compressor is protected from being started and stopped frequently. Secondly, the invention proposes to be suitable for transcritical CO 2 Control method of high-speed rail heat pump air conditioner, trans-critical CO 2 The circulating system always has the optimal exhaust pressure, the system energy efficiency ratio COP is highest under the optimal exhaust pressure, the system energy consumption is lowest, and for the system, the correlation degree of the optimal exhaust pressure and factors such as the environment temperature, the fresh air ratio, the compartment temperature and the like is higher, so the invention provides the optimal exhaust pressure correlation formula and the adjusting method of the system.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.
Claims (8)
1. A high-speed rail transcritical carbon dioxide heat pump air conditioning system is characterized by comprising: the indoor fan (10) and the fresh air valve (11) are used by two identical units and the two units together;
each of the two units comprises a compressor (1), a first electric three-way ball valve (2), a second electric three-way ball valve (3), an electronic expansion valve (4), an in-vehicle heat exchanger (5), an out-vehicle heat exchanger (6), a heat regenerator (7), a gas-liquid separator (8) and an outdoor fan (9); the outlet of the compressor (1) is communicated with the port b of the first electric three-way ball valve (2), and the port a of the first electric three-way ball valve (2) is communicated with the port c of the first electric three-way ball valve (2) through the first channel of the heat exchanger (6) outside the vehicle, the first channel of the heat regenerator (7), the electronic expansion valve (4) and the first channel of the heat exchanger (5) inside the vehicle at one time; an inlet of the compressor (1) is communicated with an e port of the second electric three-way ball valve (3) through a second channel of the heat regenerator (7) and the gas-liquid separator (8) in sequence, a d port of the second electric three-way ball valve (3) is communicated with an inlet of a first channel of the heat exchanger (6) outside the vehicle, and an f port of the second electric three-way ball valve (3) is communicated with an outlet of the first channel of the heat exchanger (5) inside the vehicle; the heat exchanger (6) outside the vehicle is provided with the outdoor fan (9); the heat exchanger (5) in the vehicle is provided with the indoor fan (10) and a fresh air valve (11); the circulating refrigerant being CO 2 。
2. The high-speed rail transcritical carbon dioxide heat pump air conditioning system according to claim 1, wherein said compressor is an inverter compressor.
3. The control method of the high-speed rail trans-critical carbon dioxide heat pump air-conditioning system of claim 1, characterized by comprising the following steps:
in the cooling operation mode, CO 2 The refrigerant flows from the port b of the first electric three-way valve to the port a and reaches the heat exchanger outside the vehicle, and flows from the port f of the second electric three-way valve to the port e and reaches the gas-liquid separator; in heating mode of operation, CO 2 The refrigerant flows from the port b to the port c of the first electric three-way valve to reach the heat exchanger in the vehicle, and flows from the port d to the port e of the first electric three-way valve to reach the gas-liquid separator;
obtaining the temperature T of the carriage i And the ambient temperature T outside the vehicle o Fresh air ratio R fresh Carriage passenger carrying rate W pass Vehicle running speed V S Current system exhaust pressure P n And a valve opening OP of the electronic expansion valve of the current system; based on the temperature T of the carriage i Selecting the number of running compressors according to the target compartment temperature; according to the temperature T of the carriage i Ambient temperature T o Fresh air ratio R fresh Carriage passenger carrying rate W pass And a vehicle running speed V s Determining the running frequency of the compressor; according to the temperature T of the carriage i External environment temperature T o Fresh air ratio R fresh Calculating the optimal exhaust pressure of the system according to the frequency of the compressor; and adjusting the valve opening of the electronic expansion valve based on the optimal exhaust pressure of the system to achieve the optimal exhaust pressure of the system to realize control.
4. The control method of the high-speed rail transcritical carbon dioxide heat pump air conditioning system according to claim 3, wherein the control method is based on the compartment temperature T i The step of selecting the number of compressor operations in relation to the target cabin temperature includes:
setting the target compartment temperature to T in the cooling operation mode cs ，T c1 Is the upper limit value, T, of the temperature fluctuation of the carriage during refrigeration c4 Is the lower limit value, T, of the temperature fluctuation of the carriage during refrigeration cs ＝1/2*(T c1 +T c4 ) Several temperature boundary values for switching the control state are respectively T c1 、T c2 、T c3 、T c4 ，T c1 ＞T c2 ＞T c3 ＞T c4 And | T c1 -T c2 |:|T c2 -T c3 |:|T c3 -T c4 |＝a 1 :a 2 :a 3 ，a 1 ＞a 2 ＞a 3 (ii) a When the temperature T of the compartment i ＞T c1 Two compressors are started in time, the frequency is operated in a higher frequency state, T c2 ＜T i ≤T c1 Two compressors are started, the frequency is operated in a medium frequency state, T c3 ＜T i ≤T c2 Two compressors are started in time, and the frequency is operated in a lower frequency state T c4 ＜T i ≤T c3 Starting a compressor, running at a lower frequency, T i ≤T c4 When the compressor is shut down and up to T i ＞T c1 Starting up the computer;
in the heating operation mode, the target cabin temperature is set to T hs ，T h1 Is the upper limit value, T, of the temperature fluctuation of the compartment during heating h4 Is the lower limit value, T, of the temperature fluctuation of the compartment during heating hs ＝1/2*(T h1 +T h4 ) Several temperature limit values for switching the control state are respectively T h1 、T h2 、T h3 、T h4 ，T h1 ＜T h2 ＜T h3 ＜T h4 And | T h1 -T h2 |:|T h2 -T h3 |:|T h3 -T h4 |＝b 1 :b 2 :b 3 ，b 1 ＞b 2 ＞b 3 When the temperature T of the compartment i ＜T h1 Two compressors are started in time, the frequency is operated in a higher frequency state, T h1 ≤T i ＜T h2 Two compressors are started, the frequency is operated in a medium frequency state, T h2 ≤T i ＜T h3 Two compressors are started in time, the frequency is operated in a lower frequency state, T h3 ≤T i ＜T h4 Starting a compressor, running at a lower frequency, T i ≥T h4 When the compressor is shut down and up to T i ＜T h1 The computer is started.
5. Root of herbaceous plantsThe control method of the high-speed rail transcritical carbon dioxide heat pump air conditioning system according to claim 4, wherein the control method is based on the compartment temperature T i External environment temperature T o Fresh air ratio R fresh Carriage passenger carrying rate W pass And a vehicle running speed V s The step of determining the operating frequency of the compressor comprises:
in the cooling operation mode, the ambient temperature T outside the vehicle is adjusted oc As a dividing line, the ambient temperature T outside the vehicle o Higher than T oc The total compressor frequency is higher than the ambient temperature T outside the vehicle o Below T oc Overall compressor frequency of time; frequency f cool The control is performed according to the following correlation:
when T is o ≥T oc When f is present cool ＝f1(T o ，T i ，R fresh ，W pass ，V s )；
When T is o ＜T oc When f is present cool ＝f2(T o ，T i ，R fresh ，W pass ，V s )；
In the heating operation mode, the ambient temperature T outside the vehicle is adjusted oh As a dividing line, the ambient temperature T outside the vehicle o Below T oh The total compressor frequency is higher than the ambient temperature T outside the vehicle o Higher than T oh Overall compressor frequency of time; frequency f heat The following correlation is used for control:
when T is o ≤T oh When f is turned on heat ＝f3(T o ，T i ，R fresh ，W pass ，V s )；
When T is o ＞T oh When f is present heat ＝f4(T o ，T i ，R fresh ，W pass ，V s )。
6. The control method of the high-speed rail transcritical carbon dioxide heat pump air conditioning system according to claim 5, wherein the control method is based on a compartment temperature T i External environment temperature T o Fresh air ratio R fresh To compressor frequency calculation systemsThe step of optimizing the exhaust pressure comprises:
according to the temperature T of the carriage i External environment temperature T o Fresh air ratio R fresh Calculating the optimal exhaust pressure p of the system with the frequency of the compressor op (ii) a Wherein the optimal refrigerating discharge pressure is p op，cool Heating optimum discharge pressure p op，heat The optimum exhaust pressure is calculated according to the following correlation: p is a radical of op，cool ＝fc(T o ，T i ，R fresh ，f cool )；p op，heat ＝fh(T o ，T i ，R fresh ，f cool )。
7. The control method of the high-speed rail trans-critical carbon dioxide heat pump air-conditioning system according to claim 6, characterized in that if the calculated system optimal exhaust pressure value is larger than 13MPa, the system optimal exhaust pressure is set to 13MPa.
8. The control method of the high-speed rail transcritical carbon dioxide heat pump air conditioning system as claimed in claim 6, wherein the step of adjusting the valve opening of the electronic expansion valve to achieve the system optimal discharge pressure based on the system optimal discharge pressure to realize control comprises:
pressure discharge value p of monitoring system n If the difference value is equal to the set pressure value p op，cool Or p op，heat The valve opening degree of the electronic expansion valve is unchanged when the absolute value is less than 0.05MPa, the valve opening degree of the electronic expansion valve is reduced when the absolute value is greater than the set discharge pressure value by 0.05MPa, the valve opening degree of the electronic expansion valve is increased when the absolute value is less than the set discharge pressure value by 0.05MPa, and the differential pressure is converted into a valve opening degree variation delta OP = C | p when the electronic expansion valve is adjusted n -p op And | C is a proportionality coefficient.
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