A control method of an air conditioning system, an air conditioning system and an air conditioner

Abstract

The application provides a control method of an air conditioning system, an air conditioning system and an air conditioner, and belongs to the technical field of air conditioners. The control method of the air conditioning system is realized based on an air conditioning system. The air conditioning system comprises a plurality of parallelly arranged secondary throttling devices. The control method comprises the following steps: acquiring the mass flow rate of refrigerant of any one secondary throttling device; obtaining the mass flow rate ratio of refrigerant of different secondary throttling devices according to the operating condition of the air conditioning system; obtaining the mass flow rate of refrigerant of another secondary throttling device according to the obtained mass flow rate ratio, and calculating the opening degree of the another secondary throttling device according to the mass flow rate, so as to realize the associated control of the plurality of different secondary throttling devices. The method can realize the decoupling control of double electronic expansion valves of a double-temperature air conditioning system, can realize the active control of different expansion valves, and is helpful to improving the stability of the double-temperature air conditioning system.

Description

Technical Field

[0001] This invention relates to the field of air conditioning technology, and in particular to a control method for an air conditioning system, an air conditioning system, and an air conditioner. Background Technology

[0002] Residential inverter heat pump air conditioners have become widespread in my country. Conventional single-temperature air conditioning systems typically use a single-suction, single-row compressor, forming a refrigeration cycle with single or multiple rows of indoor and outdoor heat exchangers to heat or cool indoor air to meet comfort requirements. This type of system uses only one electronic expansion valve, making it relatively simple and with mature control mechanisms. Because the compressor only has one pair of suction and discharge ports connected to the indoor and outdoor heat exchangers, it can only achieve one evaporation and condensation temperature, resulting in low energy consumption. To improve energy efficiency, dual-temperature air conditioning systems have emerged. These systems circulate in parallel to reduce the evaporator inlet enthalpy and have two evaporation temperatures, thus improving system cycle efficiency. However, this system uses three electronic expansion valves that are coupled together. How to control these three valves under different operating conditions is a problem that urgently needs to be solved.

[0003] Currently used control methods either directly specify the opening degree of the electronic expansion valve under various operating conditions to control the dual-temperature air conditioning system, or... This method is only applicable to fixed-point operating conditions matched with prototypes and cannot meet the requirements for efficient operation under all operating conditions. Furthermore, this control method is greatly affected by the system's manufacturing process, and the system is extremely unstable. Differences exist between individual prototypes, leading to significant deviations in the state points of different systems and failing to meet system stability requirements. Other dual-temperature air conditioning systems use conventional intake superheat or exhaust superheat parameters to control the opening degree of the electronic expansion valve. This method also suffers from instability or longer adjustment times due to the coupling between the two electronic expansion valves.

[0004] Therefore, there is an urgent need for a method to stably control dual-temperature air conditioning systems in order to control the operation of dual-temperature air conditioning systems. Summary of the Invention

[0005] To overcome the problems existing in related technologies, one of the objectives of this invention is to provide a control method for an air conditioning system. This method can achieve decoupled control of dual electronic expansion valves in a dual-temperature air conditioning system, and can achieve active control of different expansion valves, which helps to improve the stability of the dual-temperature air conditioning system.

[0006] A control method for an air conditioning system, the air conditioning system comprising a plurality of parallel-connected secondary throttling devices, the control method comprising: Obtain the mass flow rate of the refrigerant in any secondary throttling device; The refrigerant mass flow ratio of different secondary throttling devices is obtained based on the operating status of the air conditioning system. The refrigerant mass flow rate of the other secondary throttling device is obtained based on the obtained mass flow rate ratio, and the opening degree of the other secondary throttling device is calculated based on the mass flow rate, so as to realize the associated control of several different secondary throttling devices.

[0007] In a preferred embodiment of the present invention, the air conditioning system further includes a compressor, a condenser, a primary throttling device, a flash evaporator, and two evaporators connected to form a refrigeration cycle system; The primary throttling device is located between the outlet of the condenser and the inlet of the flash evaporator; two secondary throttling devices are provided, namely a first secondary throttling device and a second secondary throttling device, and the first outlet of the flash evaporator is connected to the two secondary throttling devices respectively; the two secondary throttling devices are connected in series with the inlet of an evaporator, wherein the first secondary throttling device is connected to the inlet of the first evaporator, and the second secondary throttling device is connected to the inlet of the second evaporator; The outlets of the first evaporator and the second evaporator are connected to the first suction port and the second suction port of the compressor respectively through a four-way reversing valve. The second outlet of the flash evaporator is connected to the third suction port of the compressor. The discharge port of the compressor is connected to the inlet of the condenser through a four-way reversing valve.

[0008] In a preferred embodiment of the present invention, the compressor has a first cylinder and a second cylinder, wherein the first cylinder is connected to the first evaporator and the second cylinder is connected to the second evaporator.

[0009] In a preferred embodiment of the present invention, obtaining the refrigerant mass flow rate of any one of the secondary throttling devices includes: In cooling mode: The first evaporator is obtained by the following formula: M e,H =0.06[η v,H (V res,H *f) / v suc,H ]; Among them, M e,H η is the refrigerant flow rate of the first evaporator. v,H V is the volumetric efficiency of the first cylinder of the compressor. res,H The displacement of the first cylinder of the compressor ， v suc,H is the intake specific volume of the first cylinder of the compressor, and f is the compressor frequency.

[0010] In a preferred embodiment of the present invention, the volumetric efficiency of the first cylinder of the compressor is obtained by fitting experimental data to the pressure ratio, and the relationship between the experimental data and the pressure ratio is as follows: η v =f(f,t C ,dt sat,C ,t e,H ,dt sat,suc,H ,t e,L ,dt sat,suc,L ) Among them, t C The value is the temperature at the center of the condenser, expressed in °C; t e,H The temperature at the center of the first evaporator is expressed in °C; t e,L The temperature in the middle of the second evaporator is expressed in °C (t). C , t e,H , t e,L All data were obtained from temperature sensors. dt sat,C dt is the temperature drop from the compressor's discharge port to the middle of the condenser, expressed in °C. sat,suc,H dt represents the saturation temperature drop from the middle of the first evaporator to the first suction port of the compressor, in °C. sat,suc,L The saturation temperature drop from the middle of the second evaporator to the second suction port of the compressor is expressed in °C. dt was obtained through experimental fitting. sat,C dt sat,suc,H dt sat,suc,L The fitting formula for the compressor frequency is as follows: dt sat,C =f3(f); dt sat,suc,H =f4(f); dt sat,suc,L =f5(f).

[0011] In a preferred embodiment of the present invention, the suction specific volume v of the first cylinder of the compressor suc,H It is obtained from the compressor's saturated suction specific volume and the compressor's preset superheat, where: v suc,H =f(v suc,sat,H ,dt suc,sh,H ).

[0012] v suc,sat,H This is the saturated intake specific volume of the first cylinder of the compressor, in m³ / s. 3 / kg), dt suc,sh,H The preset superheat of the first cylinder of the compressor.

[0013] In a preferred embodiment of the present invention, obtaining the refrigerant mass flow ratio of different secondary throttling devices based on the operating status of the air conditioning system includes: Obtain the intake specific volume v of the first cylinder suc,H and the intake specific volume v of the second cylinder suc,L ; According to v suc,H、 v suc,L The mass flow rate ratio between the first and second stage throttling devices and the second stage throttling device was calculated.

[0014] In a preferred embodiment of the present invention, the refrigerant mass flow ratio of different secondary throttling devices obtained according to the operating conditions of the air conditioning system is calculated using the following formula:

[0015] In a preferred embodiment of the present invention, obtaining the refrigerant mass flow rate of any one of the secondary throttling devices includes: In heating mode: Through M C =0.06[η v ((V res,L +V res,H )*f) / v suc The refrigerant flow rate of the first-stage throttling device; Calculate the intermediate temperature t FT With flash dryness x FT The total flow rate M of the two secondary throttling devices is obtained. e,H +M e,L =M C *(1-x FT ), and by determining the flow ratio r of the two secondary throttling devices. M,r Calculate the refrigerant flow rates of the first and second stage throttling devices respectively; Based on the pressure difference, mass flow rate, and inlet density of the refrigerant at the inlet and outlet of the first and second stage throttling devices, the air flow rate (L / min) corresponding to 0.1 MPa for the electronic expansion valve can be calculated. a2 V a3 Finally, the first and second stage throttling devices were determined to have Pulse2 = f(V). a2 The opening degree of the second and second stage throttling devices, Pulse3 = f(V) a3 ).

[0016] In a preferred embodiment of the present invention, the opening degree of the secondary throttling device is adjusted secondaryly through feedback regulation.

[0017] A second objective of this invention is to provide an air conditioning system for executing the air conditioning system control method described above.

[0018] A third objective of this invention is to provide an air conditioner, including the air conditioning system described above.

[0019] The beneficial effects of this invention are as follows: The present invention provides a control method for an air conditioning system. This method is based on an air conditioning system comprising several parallel-connected secondary throttling devices. The control method includes: acquiring the refrigerant mass flow rate of any one of the secondary throttling devices; obtaining the refrigerant mass flow rate ratio of different secondary throttling devices according to the operating conditions of the air conditioning system; obtaining the refrigerant mass flow rate of another secondary throttling device based on the obtained mass flow rate ratio; and calculating the opening degree of the other secondary throttling device based on the mass flow rate, thereby achieving correlated control of several different secondary throttling devices. This method, by calculating the mass flow rate ratio of different secondary throttling devices in the system and performing correlated control of different secondary throttling devices based on the mass flow rate ratio, can achieve decoupling control of the dual electronic expansion valves in a dual-temperature air conditioning system, enabling active control of different expansion valves and contributing to improved stability of the dual-temperature air conditioning system.

[0020] This application also provides an air conditioning system and an air conditioner for implementing the above control method. The air conditioning system operates stably, is sensitively controlled, and can provide consumers with a good user experience. Attached Figure Description

[0021] Figure 1 This is a flowchart of the control method for the air conditioning system provided by the present invention; Figure 2 This is a schematic diagram of the air conditioning system provided by the present invention.

[0022] Figure label: 10. Compressor; 11. First cylinder; 12. Second cylinder; 13. Third suction port; 14. Exhaust port; 20. Condenser; 31. First-stage throttling device; 32. First and second-stage throttling devices; 33. Second and second-stage throttling devices; 40. Flash evaporator; 51. First evaporator; 52. Second evaporator; 60. Four-way reversing valve. Detailed Implementation

[0023] Preferred embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the invention are shown in the drawings, it should be understood that the invention may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0024] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms “a,” “the,” and “the” used in this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0025] It should be understood that although the terms "first," "second," "third," etc., may be used in this invention to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this invention, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Thus, features defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0026] Residential inverter heat pump air conditioners have become widespread in my country. Conventional single-temperature air conditioning systems typically use a single-suction, single-row compressor, forming a refrigeration cycle with single or multiple rows of indoor and outdoor heat exchangers to heat or cool indoor air to meet comfort requirements. This type of system uses only one electronic expansion valve, making it relatively simple and with mature control mechanisms. Because the compressor only has one pair of suction and discharge ports connected to the indoor and outdoor heat exchangers, it can only achieve one evaporation and condensation temperature, resulting in low energy consumption. To improve energy efficiency, dual-temperature air conditioning systems have emerged. These systems circulate in parallel to reduce the evaporator inlet enthalpy and have two evaporation temperatures, thus improving system cycle efficiency. However, this system uses three electronic expansion valves that are coupled together. How to control these three valves under different operating conditions is a problem that urgently needs to be solved.

[0027] Current control methods either directly specify the opening degree of the electronic expansion valve under various operating conditions to control the dual-temperature air conditioning system. This method is only applicable to fixed-point operating conditions matched with prototypes and cannot meet the requirements for efficient operation under all operating conditions. Furthermore, this control method is greatly affected by the system's manufacturing process, and the system is extremely unstable. Differences exist between individual prototypes, leading to significant deviations in the state points of different systems and failing to meet system stability requirements. Other dual-temperature air conditioning systems use conventional intake superheat or exhaust superheat parameters to control the opening degree of the electronic expansion valve. This method also suffers from instability or prolonged adjustment time due to the coupling of the two electronic expansion valves. Therefore, this application provides a control method for an air conditioning system to overcome the shortcomings of the prior art.

[0028] Example 1 like Figures 1-2 As shown, a control method for an air conditioning system is provided, the air conditioning system comprising a plurality of parallel-connected secondary throttling devices, the control method comprising: S100: Obtain the mass flow rate of the refrigerant in any secondary throttling device; S200. Obtain the refrigerant mass flow ratio of different secondary throttling devices based on the operating conditions of the air conditioning system; specifically, obtaining the refrigerant mass flow ratio of different secondary throttling devices based on the operating conditions of the air conditioning system includes: S210, Obtain the intake specific volume v of the first cylinder. suc,H and the intake specific volume v of the second cylinder suc,L ; Where v suc,H、 v suc,L The calculation method is as follows: v suc,H =f(v suc,sat,H ,dt suc,sh,H ) v suc,L =f(v suc,sat,L ,dt suc,sh,L ) v suc,H、 v suc,L The units are all in m 3 / kg.

[0029] S220, according to v suc,H、 v suc,L The mass flow rate ratio between the first and second stage throttling devices is calculated. More specifically, since the flow rate calculation formula for a refrigeration system is: m = V / v * f * η, where V is the compressor volume, v is the suction specific volume, f is the frequency, and η is the volumetric efficiency, in the air conditioning system of this application, since the two cylinders of the compressor are connected to the first and second evaporators respectively, and since the volumes of the two cylinders are the same, the compressor frequency and volumetric efficiency are also the same, therefore the flow rate of the two cylinders is inversely proportional to their suction specific volume. That is, v is obtained. suc,H、 v suc,L Then, the mass flow rate ratio between the first and second stage throttling devices and the second stage throttling device can be calculated.

[0030] S300: Obtain the refrigerant mass flow rate of another secondary throttling device based on the obtained mass flow rate ratio, and calculate the opening degree of another secondary throttling device based on the mass flow rate, thereby realizing the associated control of several different secondary throttling devices.

[0031] The aforementioned air conditioning system control method is based on a dual-temperature air conditioning system, which includes several parallel-connected secondary throttling devices. The control method includes: obtaining the refrigerant mass flow rate of any one secondary throttling device; obtaining the refrigerant mass flow rate ratio of different secondary throttling devices according to the operating status of the air conditioning system; obtaining the refrigerant mass flow rate of the other secondary throttling devices based on the obtained mass flow rate ratio, and calculating the opening degree of the other secondary throttling devices based on the mass flow rate, thereby realizing the associated control of several different secondary throttling devices. This method, by calculating the mass flow rate ratio of different secondary throttling devices in the system and performing associated control of different secondary throttling devices based on the mass flow rate ratio, can achieve decoupling control of the dual electronic expansion valves in the dual-temperature air conditioning system, enabling active control of different expansion valves and helping to improve the stability of the dual-temperature air conditioning system.

[0032] More specifically, such as Figure 2 As shown. The air conditioning system also includes a compressor 10, a condenser 20, a primary throttling device 31, a flash evaporator 40, and two evaporators connected to form a refrigeration cycle system; The primary throttling device 31 is disposed between the outlet of the condenser 20 and the inlet of the flash evaporator 40; two secondary throttling devices are provided, namely a first secondary throttling device 32 and a second secondary throttling device 33, and the first outlet of the flash evaporator 40 is connected to the two secondary throttling devices respectively; the two secondary throttling devices are connected in series with the inlet of one evaporator, wherein the first secondary throttling device 32 is connected to the inlet of the first evaporator 51, and the second secondary throttling device 33 is connected to the inlet of the second evaporator 52. The overall pipeline connecting the first secondary throttling device 32 and the first evaporator 51 and the overall pipeline connecting the second secondary throttling device 33 and the second evaporator 52 are connected in parallel.

[0033] The outlets of the first evaporator 51 and the second evaporator 52 are connected to the first and second suction ports of the compressor, respectively, via a four-way reversing valve 60. The second outlet of the flash evaporator is connected to the third suction port 13 of the compressor. The discharge port 14 of the compressor is connected to the inlet of the condenser 20 via the four-way reversing valve 60. The first suction port is the inlet of the first cylinder 11 of the compressor, and the second suction port is the inlet of the second cylinder 12 of the compressor.

[0034] More specifically, the compressor has a first cylinder 11 and a second cylinder 12, wherein the first cylinder 11 is connected to the first evaporator 51 and the second cylinder 12 is connected to the second evaporator 52.

[0035] Further, obtaining the refrigerant mass flow rate of any one of the secondary throttling devices includes: In cooling mode: The first evaporator is obtained by the following formula: M e,H =0.06[η v,H (V res,H *f) / v suc,H ]; Among them, M e,H η is the refrigerant flow rate of the first evaporator. v,H V is the volumetric efficiency of the first cylinder of the compressor. res,H The displacement of the first cylinder of the compressor ， v suc,H is the intake specific volume of the first cylinder of the compressor, and f is the compressor frequency.

[0036] Furthermore, the volumetric efficiency of the first cylinder of the compressor is obtained by fitting experimental data to the pressure ratio, and the relationship between the experimental data and the pressure ratio is as follows: η v =f(f,t C ,dt sat,C ,t e,H ,dt sat,suc,H ,t e,L ,dt sat,suc,L ) Among them, t C The value is the temperature at the center of the condenser, expressed in °C; t e,H The temperature at the center of the first evaporator is expressed in °C; t e,L The temperature in the middle of the second evaporator is °C, in tons (t). C , t e,H , t e,L All data were obtained from temperature sensors. dt sat,C dt is the temperature drop from the compressor's discharge port to the middle of the condenser, expressed in °C. sat,suc,H dt represents the saturation temperature drop from the middle of the first evaporator to the first suction port of the compressor, in °C. sat,suc,L The saturation temperature drop from the middle of the second evaporator to the second suction port of the compressor is expressed in °C. dt was obtained through experimental fitting. sat,C dt sat,suc,H dt sat,suc,L The fitting formula for the compressor frequency is as follows: dt sat,C =f3(f); dt sat,suc,H =f4(f); dt sat,suc,L =f5(f).

[0037] Furthermore, the intake specific volume v of the first cylinder 11 of the compressor suc,H It is obtained from the compressor's saturated suction specific volume and the compressor's preset superheat, where: v suc,H =f(v suc,sat,H ,dt suc,sh,H ).

[0038] v suc,sat,H The saturated intake specific volume of the first cylinder 11 of the compressor, in m³ / s. 3 / kg), dt suc,sh,H The preset superheat of the first cylinder of the compressor.

[0039] Furthermore, obtaining the refrigerant mass flow ratio of different secondary throttling devices based on the operating conditions of the air conditioning system includes: Obtain the intake specific volume v of the first cylinder suc,H and the intake specific volume v of the second cylinder suc,L ; According to v suc,H、 v suc,L The mass flow rate ratio between the first and second stage throttling devices and the second stage throttling device was calculated.

[0040] Furthermore, the refrigerant mass flow ratio of different secondary throttling devices obtained according to the operating conditions of the air conditioning system is calculated using the following formula: ; Further, obtaining the refrigerant mass flow rate of any one of the secondary throttling devices includes: In heating mode: Through M C =0.06[η v ((V res,L +V res,H )*f) / v suc The refrigerant flow rate of the first-stage throttling device; Calculate the intermediate temperature t FT With flash dryness x FT The total flow rate M of the two secondary throttling devices is obtained. e,H +M e,L =M C *(1-x FT ), and by determining the flow ratio r of the two secondary throttling devices. M,r Calculate the refrigerant flow rates of the first and second stage throttling devices respectively; Based on the pressure difference, mass flow rate, and inlet density of the refrigerant at the inlet and outlet of the first and second stage throttling devices, the air flow rate (L / min) corresponding to 0.1 MPa for the electronic expansion valve can be calculated. a2 V a3 Finally, the first and second stage throttling devices were determined to have Pulse2 = f(V).a2 The opening degree of the second and second stage throttling devices, Pulse3 = f(V) a3 ).

[0041] Furthermore, after calculating the opening degree of the additional secondary throttling device based on the mass flow rate, the process also includes: The opening of the secondary throttling device is adjusted secondaryally through feedback regulation. This secondary adjustment occurs after the three electronic expansion valves have operated at their calculated openings for a period of time, and can be achieved by adjusting the suction temperature t of the compressor's first cylinder. suc1 and the temperature t in the middle of the first evaporator e,H The difference, the intake temperature t of the second cylinder of the compressor suc2 and the temperature t in the middle of the first evaporator e,L The difference is used to fine-tune the opening of the electronic expansion valve, so that Δt sh1 =(t suc1 -t e,H ) and △t sh2 =(t suc2 -t e,L When the value is 2~6℃, the opening degree is not adjusted to ensure the reliability of system operation.

[0042] This application also provides an air conditioning system for executing the air conditioning system control method described above. This air conditioning system, controlled by the aforementioned air conditioning system control method, can perform targeted control of another electronic expansion valve based on the operating status of one of the electronic expansion valves. This helps maintain the stable operation of the refrigeration system, shortens the refrigeration system's adjustment time, and enables the air conditioning system to provide consumers with a better user experience.

[0043] This application also provides an air conditioner that includes the air conditioning system described above.

[0044] The following describes in detail the control method of the air conditioning system claimed in this application, using the air conditioning system as an example. This air conditioning system uses R152a refrigerant.

[0045] The calculation of the opening degree of the two electronic expansion valves in this proposal requires the use of parameters such as detected values, preset values, and fitted values. The measured values ​​include: the temperature (t) in the middle of the first evaporator. e,H Temperature 2:t in the middle of the first evaporator e,L Temperature in the middle of the second evaporator: t C ; Condenser outlet temperature t C,out The suction temperature of the first cylinder of the compressor is 1:t. suc1 The suction temperature 2t of the second cylinder of the compressor. suc2 Compressor discharge temperature: t disCompressor frequency: f; Ambient temperature: t w Indoor ambient temperature: t N ; Preset values ​​include: the first cylinder volume V of the compressor. rev,H The compressor's second cylinder volume V rev,L The first cylinder intake superheat setpoint dt of the compressor suc,sh,H The compressor's second cylinder intake superheat setpoint dt suc,sh,L ; The parameters that need to be fitted during prototype matching include: the volumetric efficiency η of the first cylinder of the compressor and the second cylinder of the compressor. v Flow correction coefficient K of the first-stage throttling device c1 The flow correction coefficient K of the first and second stage throttling devices c2 The flow correction coefficient K of the second and second stage throttling devices c3 ρ, ρ, ρ, P, v, ρ ... suc,sat Specific enthalpy of refrigerant saturated liquid (h), latent heat of phase change of refrigerant (h) fg The saturated temperature drop dt from the outlet of the first and second stage throttling devices to the first evaporator tube sat,H The saturated temperature drop dt from the outlet of the second-stage throttling device to the second evaporator tube sat,L The saturation temperature drop dt from the middle of the first evaporator to the suction port sat,suc,H The saturation temperature drop dt from the middle of the second evaporator to the suction port sat,suc,L The saturation temperature drop dt of the exhaust gas to the middle of the condenser sat,C The opening degree of the first-stage throttling device, Pulse1 = f(V a,1 The opening degree of the first and second stage throttling devices, Pulse2 = f(V), a,2 The opening degree of the second and second stage throttling devices, Pulse3 = f(V), a,3 The second cylinder of the compressor refers to the cylinder corresponding to the compressor's suction port, which is connected to the heat exchanger on the leeward side of the room.

[0046] When the air conditioner receives the command to operate in cooling mode, it first opens the indoor unit's air deflector and starts the indoor fan according to the user-set fan speed or automatic fan speed. The outdoor fan speed, compressor frequency, and the opening of the outdoor electronic expansion valve and indoor electronic expansion valve initially operate according to the set oil return parameters. After the oil return operation is completed, the compressor frequency and outdoor fan speed operate according to the ambient temperature detected by the outdoor ambient temperature sensor and the user-set temperature parameters. The opening of the outdoor electronic expansion valve and indoor electronic expansion valve is calculated based on the temperature parameters detected by the temperature sensor.

[0047] The calculation process for the opening degree of the primary throttling device, the first and second throttling devices, and the second and third throttling devices in cooling mode is as follows: First, we know that, given the refrigerant used in the system, the correlation between the refrigerant's saturated vapor pressure and its corresponding saturated temperature, p=f(t), can be fitted using the refrigerant property software NIST. Therefore, knowing the saturated temperature at each point during system operation allows us to determine the pressure at that point. Thus: the inlet pressure of the first-stage throttling device is the saturated pressure corresponding to the condenser tube temperature, and the outlet pressure is the saturated pressure corresponding to the flash evaporator temperature (intermediate temperature). The inlet pressure of the first and second-stage throttling devices is the saturated pressure corresponding to the flash evaporator temperature, and the outlet pressure of the first and second-stage throttling devices is the saturated pressure corresponding to the sum of the first evaporator tube temperature and the saturated temperature drop from the outlet of the first and second-stage throttling devices to the first evaporator tube. The inlet pressure of the second and second-stage throttling devices is the saturated pressure corresponding to the flash evaporator temperature, and the outlet pressure of the second and second-stage throttling devices is the saturated pressure corresponding to the sum of the second evaporator tube temperature and the saturated temperature drop from the outlet of the second and second-stage throttling devices to the second evaporator tube. Knowing these basic principles, the opening degree of the three valves in the system can be calculated, as follows: Calculate the refrigerant flow rates of the first and second stage throttling devices. The first and second stage throttling devices control the suction superheat as the target, and the expression for the mass flow rate is as follows: M e,H =0.06[η v,H (V res,H *f) / v suc,H The flow rates of the first and second stage throttling devices (i.e., the flow rate of the first evaporator). M e,L =0.06[η v,L (V res,L *f) / v suc,L The flow rate of the second and second stage throttling devices (i.e., the flow rate of the second evaporator). The flow rate is mainly determined by the compressor's volumetric efficiency η. v,H η v,L The compressor has a high displacement of V in the second cylinder. res,H V res,L And the intake specific volume v of the first cylinder and the second cylinder suc,H v suc,L (Unit: m) 3 The volumetric efficiency η is determined by the weight ( / kg). v,H η v,L The relationship between the pressure ratio was fitted from the experimental data: η v =f(f,t C ,dt sat,C ,t e,H ,dt sat,suc,H ,t e,L ,dt sat,suc,L ) Where t C , te,H , t e,L These are the temperatures at the center of the condenser, and the centers of the first and second evaporators (°C), respectively, all measured by the temperature sensor. dt sat,C The saturation temperature drop from the exhaust gas to the middle of the condenser is expressed in °C and dt. sat,suc,H The saturation temperature drop from the middle of the first evaporator to the suction port, in °C, dt sat,suc,L The saturation temperature drop from the middle of the second evaporator to the suction port, in °C, are all experimentally fitted values, and are all fitted to a frequency relationship, i.e.: dt sat,C =f3(f); dt sat,suc,H =f4(f); dt sat,suc,L =f5(f); The inhalation volume can be fitted as the saturated inhalation volume v. suc,sat , (m 3 / kg) and inhalation superheat dt suc,sh The relationship between ℃ and ℃ is: v suc,H =f(v suc,sat,H ,dt suc,sh,H ); v suc,L =f(v suc,sat,L ,dt suc,sh,L ); Inhale suc,sat,H v suc,sat,L The saturated intake specific volumes of the first and second cylinders are respectively (m 3 / kg), R152a saturated gas specific volume fitting formula within the range of 0~35℃: v suc,sat =3.9287*10 -5 *t*t - 3.5776*10 -3 *t + 1.1839E-01 In the formula, temperature t is the intake saturation temperature, in °C, and the intake saturation temperature t1 of the first cylinder and the second cylinder are also mentioned. suc,H t suc,L They can be represented as: t suc,H =t e,H -dt sat,suc,H , t suc,L =t e,L -dt sat,suc,L , where dt sat,suc,H dt sat,suc,L The saturation temperature drop (°C) from the middle of the first evaporator to the suction port and the saturation temperature drop (°C) from the middle of the second evaporator to the suction port are respectively, and they can be fitted with a frequency relationship, namely: dt sat,suc,H =f4(f); dt sat,suc,L =f5(f); And dt suc,sh (dt) suc,sh,H dt suc,sh,L The first and second cylinders are the intake superheats, respectively. The saturated intake specific volumes of the two compressor cylinders and the preset intake superheat dt are known. suc,sh The specific suction volume v corresponding to the two compression cylinders of the compressor can be calculated. suc,H and v suc,L This allows us to calculate the refrigerant flow rates of the first and second stage throttling devices.

[0048] For the refrigerant flow rate of the first-stage throttling device, the target is the intermediate temperature; therefore, it is necessary to calculate the optimal intermediate temperature t of the system. FT (Flash temperature), the optimal intermediate temperature is the condenser outlet temperature t. C,out The saturation temperature t corresponding to the intake pressure of the first and second cylinders suc,H t suc,L The correlation, t suc,H =t e,H -dt sat,suc,H t suc,L =t e,L -dt sat,suc,L ,therefore: t FT =f(t C,out ,t e,H ,dt sat,suc,H ,t e,L ,dt sat,suc,L ), t C,out It is the condenser outlet temperature, in °C, which is obtained by actual measurement from the condenser outlet temperature sensing bulb.

[0049] Taking R152a refrigerant as an example, the fitting formula for its saturated vapor pressure p (Pa) is: p = 220*t*t + 7157*t + 275658; In the formula, t is the saturation temperature, in °C. Based on this formula, the pressure corresponding to the saturation temperature at each point in the system can be calculated.

[0050] Furthermore, the fitted formula for the saturated liquid specific enthalpy (kJ / kg) of R152a is: h =0.0027*t*t + 1.6719*t + 200.15; R152a latent heat of phase transition h fg The fitted formula for (kJ / kg) is: h fg = -0.0057*t*t-0.9458*t + 306.73; Therefore, the flash dryness of the flash generator can be calculated according to the above formula: xFT =(h(t C,out )-h(t FT )) / h fg (t FT ), where h(t) C,out ), h(t) FT ), h fg (t FT These are the enthalpy of the condenser outlet, the enthalpy of the flash saturated liquid, and the latent heat of flash phase change, respectively. The enthalpy of the condenser outlet is approximately equal to the enthalpy of the saturated liquid at the condenser outlet temperature.

[0051] Mass flow rate M of the first-stage throttling device c The expression for (kg / h) is as follows: M c =(M e,H +M e,L ) / (1-(1+E)x FT ); In the formula, E is the liquid-liquid ratio during parallel cylinder pumping (the ratio of liquid mass flow rate to gas mass flow rate), which is generally taken as 0, x FT This refers to flash dryness.

[0052] In summary, the mass and flow rate of the primary throttling device, the first and second-stage throttling devices, and the second and third-stage throttling devices can all be calculated. The inlet and outlet pressures of the electronic expansion valve can be calculated based on the saturation pressure corresponding to the saturation temperature at the valve's inlet and outlet. The inlet refrigerant density of the electronic expansion valve, in refrigeration mode, is that of a subcooled liquid refrigerant at the inlet of the primary throttling device, and its density can be approximated as the density of a saturated liquid. The inlet refrigerant of the first and second-stage throttling devices is also a saturated liquid, and both can be calculated using the correlation between saturated liquid density and the saturation temperature corresponding to the pressure, fitted by the refrigerant property calculation software NIST, i.e., ρ. i =f(t). Saturated density of R152a (kg / m³) 3 Fitting formula: ρ= -0.0086*t*t-2.1328*t +958.44; Given the pressure difference, mass flow rate, and inlet density of the refrigerant at the inlet and outlet of the electronic expansion valve, the corresponding air flow rate (L / min) at 0.1 MPa can be calculated, including the air flow rate (L / min) of the first-stage throttling device: V a,1 =K c1 *M C / (ρ 1,i *sqrt(△P) r,C ); Air flow rate of the first and second stage throttling devices: V a,2 =K c2 *Me,H / (ρ 2,i *sqrt(△P) r,H ); Airflow rate of the second and second stage throttling devices: V a,3 =K c3 *M e,L / (ρ 2,i *sqrt(△P) r,L ); Given that the primary throttling device, the first and second throttling devices, and the second and third throttling devices correspond to an air flow rate V of 0.1 MPa. a1 and V a2 V a3 The opening degree of the first-stage throttling device, Pulse1=f(V), is calculated respectively. a1 ), the opening degree of the first and second stage throttling devices Pulse2 = f(V a2 The opening degree of the second and second stage throttling devices, Pulse3 = f(V) a3 ).

[0053] After the three electronic expansion valves have been running at their calculated openings for a period of time, the suction temperature t can be used to determine the temperature. suc1 and the temperature t in the middle of the first evaporator e,H The difference, intake temperature t suc2 and the temperature t in the middle of the first evaporator e,L The difference is used to fine-tune the opening of the electronic expansion valve, so that Δt sh1 =(t suc1 -t e,H ) and △t sh2 =(t suc2 -t e,L The opening is not adjusted when the temperature is 2-6℃ to ensure reliable operation.

[0054] It should be noted that the opening degree of the first-stage throttling device, Pulse1 = f(V), is... a,1 The opening degree of the first and second stage throttling devices, Pulse2 = f(V), a,2 The opening degree of the second and second stage throttling devices, Pulse3 = f(V), a,3 By fitting the relationship between refrigerant flow rate and opening degree, and then obtaining the refrigerant flow rate, the corresponding opening degree of the throttling device can be directly obtained. For example, based on prior information, a correspondence diagram between the refrigerant flow rate and opening degree of the first and second-level throttling devices can be obtained. Then, during subsequent use, based on the current refrigerant flow rate in the first and second-level throttling devices, the current opening degree of the first and second-level throttling devices can be directly found from the correspondence diagram between the refrigerant flow rate and opening degree of the first and second-level throttling devices.

[0055] The calculation flowchart for the three electronic expansion valves in heating mode is as follows: Its calculation process is similar to that of the cooling mode, firstly through M C =0.06[η v ((V res,L +V res,H )*f) / v suc Calculate the flow rate of the first-stage throttling device. At this point, the outdoor side is the evaporator, the indoor side is the condenser, and the suction pressure of the two suction cylinders of the compressor is the same. Therefore, the displacement of the compressor at this point is V. res,L +V res,H Therefore, the flow rate M of the first-stage throttling device can be calculated. C Based on the pressure difference across the primary throttling device and the density of the inlet refrigerant, the corresponding air flow rate V at 0.1 MPa can be calculated. a1 Then the intermediate temperature t was calculated. FT With flash dryness x FT Thus, the total flow rate M of the first and second stage throttling devices can be determined. e,H +M e,L =M C *(1-x FT The flow rate ratio of the first and second stage throttling devices to the second stage throttling device is r. M,r This can be determined during the initial prototype matching process and can be fitted into a relationship r between the condensation temperature and the condensation temperature. M,r =M e,H / M e,L =f(t e,H ,t e,L Furthermore, the refrigerant flow rates of the first and second stage throttling devices can be determined separately. Based on the pressure difference, mass flow rate, and inlet density of the refrigerant at the inlet and outlet of the first and second stage throttling devices, the corresponding air flow rate (L / min) at 0.1 MPa for the electronic expansion valve can be calculated. a2 V a3 Finally, the opening degree of the first and second stage throttling devices is determined as Pulse2 = f(V). a2 The opening degree of the second and second stage throttling devices, Pulse3 = f(V) a3 ).

[0056] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings. In the description of this application, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0057] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0058] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, these terms have no special meaning and therefore should not be construed as limiting the scope of protection of this application. The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A control method for an air conditioning system, the air conditioning system comprising a plurality of parallel-connected secondary throttling devices, characterized in that, In an air conditioning system, different evaporators are connected in series with a throttle valve. The compressor has a first cylinder and a second cylinder, with the first cylinder connected to a first evaporator and the second cylinder connected to a second evaporator. The control method includes: Obtain the mass flow rate of the refrigerant in any secondary throttling device; The refrigerant mass flow ratio of different secondary throttling devices is obtained based on the operating status of the air conditioning system. The refrigerant mass flow rate of the other secondary throttling device is obtained based on the obtained mass flow rate ratio, and the opening degree of the other secondary throttling device is calculated based on the mass flow rate, so as to realize the associated control of several different secondary throttling devices.

2. The control method for an air conditioning system according to claim 1, characterized in that: The air conditioning system also includes a compressor, a condenser, a primary throttling device, a flash evaporator, and two evaporators connected to form a refrigeration cycle system; The primary throttling device is disposed between the outlet of the condenser and the inlet of the flash evaporator; two secondary throttling devices are provided, namely a first secondary throttling device and a second secondary throttling device, and the first outlet of the flash evaporator is connected in series with the two secondary throttling devices; The two secondary throttling devices are connected in series with the inlet of one of the evaporators, wherein the first secondary throttling device is connected to the inlet of the first evaporator, and the second secondary throttling device is connected to the inlet of the second evaporator; The outlets of the first evaporator and the second evaporator are connected to the first and second suction ports of the compressor respectively via a four-way reversing valve. The second outlet of the flash evaporator is connected to the third suction port of the compressor. The discharge port of the compressor is connected to the inlet of the condenser via a four-way reversing valve.

3. The control method for the air conditioning system according to claim 2, characterized in that: The process of obtaining the refrigerant mass flow rate of any secondary throttling device includes: In cooling mode: The first evaporator is obtained by the following formula: M e,H =0.06[η v,H (V res,H *f) / v suc,H ]; Among them, M e,H η is the refrigerant flow rate of the first evaporator. v,H V is the volumetric efficiency of the first cylinder of the compressor. res,H The displacement of the first cylinder of the compressor ， v suc,H denoted as ρ, where ρ is the intake specific volume of the first cylinder of the compressor, and f is the compressor frequency.

4. The control method for the air conditioning system according to claim 2, characterized in that: The volumetric efficiency of the first cylinder of the compressor was obtained by fitting experimental data to the pressure ratio. The relationship between the experimental data and the pressure ratio is as follows: η v =f(f,t C ,dt sat,C ,t e,H ,dt sat,suc,H ,t e,L ,dt sat,suc,L ) Among them, t C The value is the temperature at the center of the condenser, expressed in °C; t e,H The temperature at the center of the first evaporator, in °C; t e,L The temperature in the middle of the second evaporator is °C, in tons (t). C , t e,H , t e,L All data were obtained from temperature sensors. dt sat,C dt is the temperature drop from the compressor's discharge port to the middle of the condenser, expressed in °C. sat,suc,H dt represents the saturation temperature drop from the middle of the first evaporator to the first suction port of the compressor, in °C. sat,suc,L The saturation temperature drop from the middle of the second evaporator to the second suction port of the compressor is expressed in °C. dt was obtained through experimental fitting. sat,C dt sat,suc,H dt sat,suc,L The fitting formula for the compressor frequency is as follows: dt sat,C =f3(f) ;dt sat,suc,H =f4(f);dt sat,suc,L =f5(f)。 5. The control method for an air conditioning system according to claim 3, characterized in that: The suction specific volume v of the first cylinder of the compressor suc,H It is obtained from the compressor's saturated suction specific volume and the compressor's preset superheat, where: v suc,H =f(v suc,sat,H ,dt suc,sh,H ); v suc,sat,H This is the saturated intake specific volume of the first cylinder of the compressor, in m³ / s. 3 / kg), dt suc,sh,H The preset superheat of the first cylinder of the compressor.

6. The control method for the air conditioning system according to claim 3, characterized in that: The process of obtaining the refrigerant mass flow ratio of different secondary throttling devices based on the operating status of the air conditioning system includes: Obtain the intake specific volume v of the first cylinder suc,H and the intake specific volume v of the second cylinder suc,L ; According to v suc,H、 v suc,L The mass flow rate ratio between the first and second stage throttling devices and the second stage throttling device was calculated.

7. The control method for an air conditioning system according to claim 5, characterized in that: The refrigerant mass flow ratio of different secondary throttling devices obtained according to the operating conditions of the air conditioning system is calculated using the following formula: 。 8. The control method for an air conditioning system according to claim 6, characterized in that: The process of obtaining the refrigerant mass flow rate of any secondary throttling device includes: In heating mode: Through M C =0.06[η v ((V res,L +V res,H )*f) / v suc The refrigerant flow rate of the first-stage throttling device; Calculate the intermediate temperature t FT With flash dryness x FT The total flow rate M of the two secondary throttling devices is obtained. e,H +M e,L =M C *(1-x FT ), and by determining the flow ratio r of the two secondary throttling devices. M,r Calculate the refrigerant flow rates of the first and second stage throttling devices respectively; Based on the pressure difference, mass flow rate, and inlet density of the refrigerant at the inlet and outlet of the first and second stage throttling devices, the air flow rate (L / min) corresponding to 0.1 MPa for the electronic expansion valve can be calculated. a2 V a3 Finally, it was determined that the first and second stage throttling devices Pulse2 = f(V) a2 The opening degree of the second and second stage throttling devices, Pulse3 = f(V) a3 ).

9. The control method for an air conditioning system according to claim 6, characterized in that: After calculating the opening degree of the additional secondary throttling device based on the mass flow rate, it also includes: The opening of the secondary throttling device is adjusted secondary by feedback regulation.

10. An air conditioning system, characterized in that, In the air conditioning system, different evaporators are connected in series with a throttle valve, and the compressor has a first cylinder and a second cylinder, wherein the first cylinder is connected to the first evaporator and the second cylinder is connected to the second evaporator; the air conditioning system is used to execute the control method of the air conditioning system as described in any one of claims 1-9.

11. An air conditioner, characterized in that, Including the air conditioning system as described in claim 10.

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