CN113137691A - Control method of magnetic suspension air conditioning unit - Google Patents
Control method of magnetic suspension air conditioning unit Download PDFInfo
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- CN113137691A CN113137691A CN202110241548.5A CN202110241548A CN113137691A CN 113137691 A CN113137691 A CN 113137691A CN 202110241548 A CN202110241548 A CN 202110241548A CN 113137691 A CN113137691 A CN 113137691A
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- 239000000725 suspension Substances 0.000 title claims abstract description 151
- 238000000034 method Methods 0.000 title claims abstract description 61
- 238000004378 air conditioning Methods 0.000 title claims abstract description 58
- 239000003507 refrigerant Substances 0.000 claims description 70
- 238000005339 levitation Methods 0.000 claims description 49
- 238000004891 communication Methods 0.000 claims description 3
- 230000000694 effects Effects 0.000 abstract description 5
- 238000001816 cooling Methods 0.000 description 21
- 239000000498 cooling water Substances 0.000 description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 17
- 239000007788 liquid Substances 0.000 description 5
- 230000009467 reduction Effects 0.000 description 5
- 230000009471 action Effects 0.000 description 4
- 230000008901 benefit Effects 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 238000001035 drying Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 1
- 238000012790 confirmation Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F11/00—Control or safety arrangements
- F24F11/30—Control or safety arrangements for purposes related to the operation of the system, e.g. for safety or monitoring
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F11/00—Control or safety arrangements
- F24F11/50—Control or safety arrangements characterised by user interfaces or communication
- F24F11/61—Control or safety arrangements characterised by user interfaces or communication using timers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F11/00—Control or safety arrangements
- F24F11/62—Control or safety arrangements characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
- F24F11/63—Electronic processing
- F24F11/64—Electronic processing using pre-stored data
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F11/00—Control or safety arrangements
- F24F11/70—Control systems characterised by their outputs; Constructional details thereof
Abstract
The invention relates to the technical field of air conditioners, and particularly provides a control method of a magnetic suspension air conditioning unit, aiming at solving the technical problem that the pressure relief speed is low in the existing control method. The pressure relief bypass of the unit comprises a pressure relief switch valve and a pressure relief throttling element which are arranged in parallel, and the control method comprises the following steps: when the shunting unit meets the shutdown condition, acquiring the current pressure ratio of the compressor; comparing the magnitude relationship between the current pressure ratio and the allowable shutdown pressure ratio threshold; and selectively and directly controlling the compressor to stop or opening the pressure relief switch valve and the pressure relief throttling element to adjust the pressure ratio until the condition of stopping the compressor is achieved according to the comparison result. The invention can utilize the throttling and pressure reducing functions of the throttling element and the switching value characteristic of the pressure relief switch valve, has obvious instantaneous pressure relief effect after being switched on, enables the pressure ratio to quickly reach the pressure ratio threshold value of the compressor allowed shutdown, is particularly important for emergency fault unloading shutdown, and reduces the risk of bearing damage of the magnetic suspension centrifugal compressor.
Description
Technical Field
The invention belongs to the technical field of air conditioners, and particularly provides a control method of a magnetic suspension air conditioning unit.
Background
With the continuous development of science and technology, the magnetic suspension air conditioning unit becomes a very common air conditioning unit.
The core technology of the magnetic suspension air conditioning unit lies in a magnetic suspension centrifugal compressor adopted by the unit, the magnetic suspension centrifugal compressor generally comprises a rotating shaft, a magnetic bearing, a standby bearing and a positioning sensor, and the rotating shaft can be suspended above the magnetic bearing and generate high-speed rotation to improve the gas flow rate; when the rotating shaft stops rotating, the rotating shaft can fall onto the bearing, so that the bearing can support the rotating shaft which stops rotating; the positioning sensor can detect the position of the rotating shaft in real time so as to effectively judge whether the rotating shaft deviates from the original rotating center in the rotating process. When an existing magnetic suspension air conditioning unit receives a stop instruction, a magnetic suspension centrifugal compressor is usually stopped immediately, although the process of stopping the rotation of a rotating shaft usually needs to take several seconds; however, the gas on the high pressure side flows in the opposite direction under the action of pressure, the acting force applied to the rotating shaft of the compressor exceeds the supporting force provided by the magnetic bearings, the rotating shaft does not stop rotating, and the rotating shaft rotating at high speed causes great impact on the bearings, so that the bearings are easily damaged. Particularly, when the pressure ratio of the magnetic suspension centrifugal compressor is high during the shutdown, the surging phenomenon of the magnetic suspension centrifugal compressor is easily caused by suddenly reducing the rotating speed of the rotating shaft, so that the rotating shaft continuously impacts the bearing, and the bearing is damaged.
Therefore, the chinese patent publication No. CN109855338A discloses an air-cooled magnetic suspension centrifugal unit, which is provided with a pressure release valve, and the pressure release valve 6 is connected in parallel with the magnetic suspension centrifugal compressor 1 and the evaporator 5, so that the pressure ratio of the magnetic suspension centrifugal compressor 1 can be reduced when the pressure release valve 6 is opened, thereby achieving the pressure release effect, referring to paragraph [ 0024 ] of the specification and attached drawing 1. Further, referring to paragraphs [ 0026 ] to [ 0036 ] of the specification, the patent document of the invention also discloses a shutdown control method of the air-cooled magnetic suspension centrifugal machine set, which mainly comprises the following steps: s1: after a shutdown instruction is received, the magnetic suspension centrifugal compressor is decompressed; s2: acquiring the pressure ratio of the magnetic suspension centrifugal compressor within a first preset time; s3: and enabling the magnetic suspension centrifugal compressor to enter a corresponding shutdown mode according to the pressure ratio of the magnetic suspension centrifugal compressor within the first preset time.
Although this patent document discloses a method of reducing the pressure ratio of the compressor by a pressure relief valve, it does not clearly indicate which pressure relief valve is used and how to relieve the pressure. Therefore, the chinese patent publication No. CN108954650B also discloses a control method for an air-cooled magnetic levitation air conditioner, in which a bypass electronic expansion valve is connected in series between the exhaust port of the magnetic levitation centrifugal compressor and the evaporator, so as to adjust the pressure ratio of the air conditioning unit through the bypass electronic valve.
However, the electronic expansion valve is opened linearly, the unloading of the electronic expansion valve is greatly influenced by time, and the problem that the pressure ratio cannot be quickly adjusted to a stop condition due to the slow pressure ratio adjusting speed exists. Normally, the pressure relief speed of the unit is increased by selecting a larger electronic expansion valve, but the measure increases the manufacturing cost of the unit.
In view of this, a need exists for a new method for solving the technical problem of slow pressure release speed of the existing control method of the magnetic suspension air conditioning unit.
Disclosure of Invention
The invention provides a control method of a magnetic suspension air conditioning unit, aiming at solving the technical problem that the pressure relief speed of the control method of the existing magnetic suspension air conditioning unit is low.
The invention discloses a magnetic suspension air conditioning unit, which comprises a pressure relief bypass for relieving pressure of a magnetic suspension centrifugal compressor, and is characterized in that the pressure relief bypass comprises a pressure relief switch valve and a pressure relief throttling element which are arranged in parallel, and the control method applicable to the magnetic suspension air conditioning unit comprises the following steps: when the magnetic suspension air conditioning unit meets a shutdown condition, acquiring the current pressure ratio of the magnetic suspension centrifugal compressor; comparing the magnitude relationship between the current pressure ratio and a threshold allowable shutdown pressure ratio; and selectively and directly controlling the magnetic suspension centrifugal compressor to stop or starting the pressure relief switch valve and the pressure relief throttling element to adjust the pressure ratio until the condition that the magnetic suspension centrifugal compressor stops is reached according to the comparison result.
In a preferred embodiment of the above control method of the present invention, the "selectively and directly controlling the magnetic suspension centrifugal compressor to stop or starting the pressure relief switch valve and the pressure relief throttling element to adjust the pressure ratio until reaching the condition of stopping the magnetic suspension centrifugal compressor according to the comparison result" includes the following steps: and when the current pressure ratio is smaller than or equal to the allowable shutdown pressure ratio threshold value, directly controlling the magnetic suspension centrifugal compressor to be shut down.
In a preferred embodiment of the above control method of the present invention, the "selectively and directly controlling the magnetic suspension centrifugal compressor to stop or starting the pressure relief switch valve and the pressure relief throttling element to adjust the pressure ratio until reaching the condition of stopping the magnetic suspension centrifugal compressor according to the comparison result" includes the following steps: and when the current pressure ratio is greater than the threshold value of the allowable shutdown pressure ratio, opening the pressure relief switch valve and the pressure relief throttling element to adjust the pressure ratio until the shutdown condition of the magnetic suspension centrifugal compressor is reached.
In a preferable aspect of the above control method of the present invention, when the current pressure ratio is greater than the allowable shutdown pressure ratio threshold, the control method further includes the steps of: keeping the magnetic suspension centrifugal compressor to operate in the current state for a preset time; comparing the magnitude relation between the current pressure ratio of the magnetic suspension centrifugal compressor and the allowable shutdown pressure ratio threshold value again; and selectively and directly controlling the magnetic suspension centrifugal compressor to stop according to the result of the comparison again, or opening the pressure relief switch valve and the pressure relief throttling element to adjust the pressure ratio until the condition that the magnetic suspension centrifugal compressor stops is reached.
In a preferable embodiment of the above control method of the present invention, "selectively and directly controlling the magnetic suspension centrifugal compressor to stop or opening the pressure relief switch valve and the pressure relief throttling element to adjust the pressure ratio until a condition that the magnetic suspension centrifugal compressor stops is reached according to a result of the comparison again" includes the following steps: and when the result of the comparison again shows that the current pressure ratio is greater than the threshold value of the allowable shutdown pressure ratio, opening the pressure relief switch valve and the pressure relief throttling element to adjust the pressure ratio until the shutdown condition of the magnetic suspension centrifugal compressor is reached.
In a preferable embodiment of the above control method of the present invention, "selectively and directly controlling the magnetic suspension centrifugal compressor to stop or opening the pressure relief switch valve and the pressure relief throttling element to adjust the pressure ratio until a condition that the magnetic suspension centrifugal compressor stops is reached according to a result of the comparison again" includes the following steps: and when the current pressure ratio is smaller than or equal to the allowable stop pressure ratio threshold value as a result of the comparison again, directly controlling the magnetic suspension centrifugal compressor to stop.
In a preferable embodiment of the above control method of the present invention, the method for determining whether the condition for stopping the magnetic levitation centrifugal compressor is met in the "condition for opening the pressure relief switch valve and the pressure relief throttling element to adjust the pressure ratio until the condition for stopping the magnetic levitation centrifugal compressor is met" includes the following steps: judging whether the opening time of the pressure relief switch valve reaches a first preset time; otherwise, returning to the step of comparing the magnitude relation between the current pressure ratio of the magnetic suspension centrifugal compressor and the allowable stop pressure ratio threshold again.
In a preferable mode of the above control method according to the present invention, after the compressor is controlled to stop, the control method further includes the steps of: keeping the opening of the pressure relief switch valve for a second preset time; and closing the pressure relief switch valve.
In a preferable embodiment of the control method of the present invention, the magnetic levitation air conditioning unit further includes a one-way conduction bypass, and the one-way conduction bypass is configured to allow a refrigerant to flow from an exhaust port of the compressor to a refrigerant inlet of the condenser in a one-way manner.
In a preferable embodiment of the control method of the present invention, the one-way bypass includes a one-way valve, the discharge port of the compressor and the refrigerant inlet of the condenser are communicated through the one-way valve, and the one-way valve allows a refrigerant to flow from the discharge port of the compressor to the refrigerant inlet of the condenser in a one-way manner.
The invention relates to a magnetic suspension air conditioning unit, which comprises a pressure relief bypass for relieving pressure of a magnetic suspension centrifugal compressor, wherein the pressure relief bypass comprises a pressure relief switch valve and a pressure relief throttling element which are arranged in parallel, and the control method applicable to the magnetic suspension air conditioning unit comprises the following steps: when the magnetic suspension air conditioning unit meets the shutdown condition, acquiring the current pressure ratio of the magnetic suspension centrifugal compressor; comparing the magnitude relationship between the current pressure ratio and the allowable shutdown pressure ratio threshold; and selectively and directly controlling the magnetic suspension centrifugal compressor to stop or starting the pressure relief switch valve and the pressure relief throttling element to adjust the pressure ratio until the condition that the magnetic suspension centrifugal compressor stops is achieved according to the comparison result.
Compared with the prior art that the pressure is simply released through the electronic expansion valve, the invention has the advantages of low pressure release cost and high price advantage by adopting the switch valve if the bypass has the same refrigerating capacity. In addition, the electronic expansion valve is linearly opened, the pressure relief is greatly influenced by time, the pressure relief speed is low, the pressure relief bypass is connected with the pressure relief switch valve and the pressure relief throttling element in parallel, the throttling and pressure reducing functions of the throttling element can be utilized, the switching value characteristic of the pressure relief switch valve can be utilized, the instant pressure relief effect after opening is obvious, the defect that the pressure relief of the throttling element is influenced by time can be compensated, the pressure ratio can quickly reach the allowable shutdown pressure ratio threshold value of the magnetic suspension centrifugal compressor, the point is particularly important for emergency fault unloading shutdown, the shutdown safety and reliability of the magnetic suspension centrifugal compressor can be improved, and the risk of bearing damage of the magnetic suspension centrifugal compressor can be reduced.
Drawings
FIG. 1 is a schematic structural diagram of a particular embodiment of a magnetic levitation air conditioning unit of the present invention;
FIG. 2 is a main control flow step of the control method of the magnetic suspension air conditioning unit of the invention;
fig. 3 is a detailed control flow step of the control method of the magnetic levitation air conditioning unit of the present invention.
Wherein, the one-to-one correspondence between the names of the components and the reference numbers in fig. 1 is as follows:
1, a magnetic suspension centrifugal compressor;
2 condenser, 2iCooling water inlet, 2oA cooling water outlet;
evaporator, 3iChilled water inlet, 3oA chilled water outlet;
4 a main path throttling element;
5, an economizer: 5a refrigerant inlet of a first refrigerant channel, 5b a refrigerant inlet of a second refrigerant channel, 5c a refrigerant outlet of the first refrigerant channel, 5d a refrigerant outlet of the second refrigerant channel, 51 an economizer side throttling element, 52 an economizer side pressure sensor and 53 an economizer side temperature sensor;
6 drying the filter;
7, pressure relief bypass: 70 a pressure relief throttling element, 71 a pressure relief switching element;
8, a one-way valve;
90 cool the on-off valve, 91 cool the filter.
Detailed Description
Preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only for explaining the technical principle of the present invention, and are not intended to limit the scope of the present invention.
It should be noted that, in the description of the present application, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In order to facilitate understanding of the control method of the magnetic levitation air conditioning unit of the present invention, the following takes a water-cooling magnetic levitation air conditioning unit as an example with reference to fig. 1, and first, the main structure and the operation principle of such an air conditioning unit are described in detail. Fig. 1 is a schematic structural diagram of a magnetic levitation air conditioning unit according to an embodiment of the present invention. In fig. 1, solid arrows "→" represent the refrigerant flow direction of the air conditioning unit, and broken arrows
Representing the flow direction of the cooling water and the chilled water of the air conditioning unit.
Referring to fig. 1, in the present embodiment, the water-cooled magnetic levitation air conditioning unit at least includes a magnetic levitation centrifugal compressor 1, a condenser 2, an evaporator 3, and a main path throttling element 4. The magnetic suspension centrifugal compressor 1, the condenser 2, the main path throttling element 4 and the evaporator 3 are sequentially connected in an end-to-end mode through pipelines to form a refrigerant main circulation loop.
As mentioned above, the condenser 2 in this embodiment is a water-cooled condenser 2, two heat exchange medium channels are provided in the water-cooled condenser 2, and the media in the two heat exchange medium channels exchange heat with each other when there is a temperature difference. One path of the two paths of heat exchange medium channels is a refrigerant channel, and the other path of the two paths of heat exchange medium channels is a cooling water channel, wherein the refrigerant channel is provided with a refrigerant inlet and a refrigerant outlet which are communicated with the main path pipeline, and the cooling water channel is provided with a cooling water inlet 2 which is communicated with an external cooling water circulation pipelineiAnd a cooling water outlet 2o。
With reference to fig. 1, in this embodiment, the evaporator 3 is a water-cooled evaporator 3, the water-cooled evaporator 3 also has two medium channels, and the media in the two medium channels can exchange heat with each other when there is a temperature differenceAnd (4) changing. One of the two medium channels is a refrigerant channel, the other is a chilled water channel, wherein the refrigerant channel is provided with a refrigerant inlet and a refrigerant outlet which are communicated with the main pipeline, and the chilled water channel is provided with a chilled water inlet 3 which is communicated with an external chilled water circulation pipelineiAnd a chilled water outlet 3o。
The refrigerant inlet of the condenser 2 is communicated with the exhaust port of the magnetic suspension centrifugal compressor 1 through a main path pipeline and other auxiliary elements, the refrigerant outlet of the condenser is communicated with the refrigerant inlet of the evaporator 3 through the main path pipeline, the main path throttling element 4 and other auxiliary elements, and the refrigerant outlet of the evaporator 3 is communicated with the air suction port of the magnetic suspension centrifugal compressor 1 through the main path pipeline and other auxiliary elements.
The working principle of a main circulation loop of the magnetic suspension air conditioning unit is as follows: starting the external cooling water circulation loop and the chilled water circulation loop, under the action of the circulation power provided by the external power element, cooling water enters the cooling water channel from the cold water inlet of the condenser 2, and chilled water enters the chilled water channel from the chilled water inlet 3 of the evaporator 3iEntering a chilled water channel; meanwhile, the magnetic suspension centrifugal compressor 1 is started, low-temperature and low-pressure gaseous refrigerant enters the magnetic suspension centrifugal compressor 1, the gaseous refrigerant is compressed by the magnetic suspension centrifugal compressor 1 to form high-temperature and high-pressure gaseous refrigerant, the gaseous refrigerant enters a refrigerant channel of the condenser 2, the gaseous refrigerant exchanges heat with cooling water in a cooling water channel to release heat and cool the gaseous refrigerant to form medium-temperature and high-pressure liquid refrigerant, and cooling water absorbs heat and heats the liquid refrigerant from a cooling water outlet 2oReturning to the external cooling water circulation pipeline, the medium-temperature high-pressure liquid refrigerant is throttled and depressurized by the main path throttling element 4 to form a low-temperature low-pressure two-phase mixed refrigerant, the low-temperature low-pressure two-phase mixed refrigerant enters the refrigerant channel of the evaporator 3, the low-temperature low-pressure two-phase mixed refrigerant exchanges heat with the frozen water in the frozen water channel to absorb heat and raise the temperature to form a low-temperature low-pressure gaseous refrigerant, the low-temperature low-pressure gaseous refrigerant returns to the magnetic suspension centrifugal compressor 1 from the air suction port, the frozen water releases heat and is cooled, and then the temperature of the frozen water is reduced from the frozen water outlet 3oAnd returning the refrigerant to the external chilled water circulation loop, and circulating to provide heated cooling water or cooled chilled water for a user.
As described above and shown in fig. 1, in addition to the indispensable functional elements of the magnetic levitation centrifugal compressor 1, the condenser 2, the main path throttling element 4 and the evaporator 3, the magnetic levitation air conditioning unit of the present embodiment further includes other auxiliary elements, and the names, the connection relationships and the functions of these auxiliary elements with other main functional elements will be described in detail later in conjunction with fig. 1.
As described in the background art, the magnetic levitation air conditioning unit usually stops the magnetic levitation centrifugal system immediately when receiving a shutdown command, although the process of stopping the rotation of the rotating shaft usually takes several seconds; however, the gas at the high pressure side flows reversely under the action of pressure, the acting force applied to the rotating shaft of the magnetic suspension centrifugal compressor 1 exceeds the supporting force provided by the magnetic bearing, the rotating shaft usually does not stop rotating, and the rotating shaft rotating at high speed can cause great impact to the bearing, so that the bearing is easily damaged; particularly, when the pressure ratio of the magnetic suspension centrifugal compressor 1 is high during the shutdown, the rapid reduction of the rotation speed of the rotating shaft easily causes the magnetic suspension centrifugal compressor 1 to generate a surge phenomenon, so that the rotating shaft continuously impacts the bearing, and the bearing is damaged.
Therefore, in the embodiment, the pressure relief bypass 7 is additionally arranged in the magnetic suspension air conditioning unit, and a control method of the magnetic suspension air conditioning unit is provided on the basis of the structural improvement, so that the pressure relief is rapidly carried out on the unit when the pressure ratio of the magnetic suspension centrifugal compressor 1 is high, the pressure ratio of the magnetic suspension centrifugal compressor 1 rapidly reaches the threshold value of the allowable shutdown pressure ratio, and the risk of bearing damage caused by shutdown of the magnetic suspension centrifugal compressor 1 is reduced.
In detail, with continued reference to fig. 1, the pressure relief bypass 7 includes a pressure relief switching element 71 and a pressure relief throttling element 70 arranged in parallel, and the pressure relief bypass 7 communicates the exhaust port of the magnetically levitated centrifugal compressor 1 and the evaporator 3, and the pressure relief bypass 7 is used for relieving the pressure of the magnetically levitated centrifugal compressor 1.
The following describes in detail the control method for the improved magnetic levitation air conditioning unit provided by the present invention with reference to fig. 2, and fig. 2 is a flowchart of main steps of the control method for the magnetic levitation air conditioning unit of the present invention.
The control method comprises the following steps:
when the unit meets the shutdown condition, acquiring the current pressure ratio of the magnetic suspension centrifugal compressor 1;
comparing the magnitude relation between the current pressure ratio of the magnetic suspension centrifugal compressor 1 and the allowable shutdown pressure ratio threshold value;
according to the comparison result, the magnetic suspension centrifugal compressor 1 is selectively and directly controlled to stop or the pressure relief switch element 71 and the pressure relief throttling element 70 are opened to adjust the pressure ratio until the pressure ratio reaches the allowable stop pressure ratio threshold value, and then the magnetic suspension centrifugal compressor 1 is controlled to stop.
In detail, "selectively and directly controlling the magnetic levitation centrifugal compressor 1 to stop or start the pressure relief switching element 71 and the pressure relief throttling element 70 to adjust the pressure ratio until the magnetic levitation centrifugal compressor 1 stops after the pressure ratio reaches the threshold value of the allowable stop pressure ratio according to the comparison result" includes the following steps:
when the current pressure ratio of the magnetic suspension centrifugal compressor 1 is larger than the threshold value of the pressure ratio of the allowable shutdown, directly controlling the magnetic suspension centrifugal compressor 1 to shutdown.
When the current pressure ratio of the magnetic suspension centrifugal compressor 1 is smaller than or equal to the threshold value of the allowable shutdown pressure ratio, the pressure relief switch element 71 and the pressure relief throttling element 70 are started to adjust the pressure ratio until the pressure ratio reaches the threshold value of the allowable shutdown pressure ratio, and then the magnetic suspension centrifugal compressor 1 is controlled to be shut down.
Compared with the prior art that the pressure is simply released through the electronic expansion valve, the invention has the advantages of low pressure release cost and high price advantage by adopting the switch valve if the bypass has the same refrigerating capacity. In addition, the electronic expansion valve is opened linearly, the pressure relief is influenced by time greatly, and the pressure relief speed is slow, but the pressure relief bypass 7 of the invention is connected with the pressure relief switch element 71 and the pressure relief throttling element 70 in parallel, not only can utilize the throttling and pressure reduction functions of the throttling element, but also can utilize the switching value characteristics of the pressure relief switch element 71, the instant pressure relief effect is obvious after the opening, the deficiency that the pressure relief of the throttling element is influenced by time can be compensated, the pressure ratio can quickly reach the shutdown pressure ratio threshold value allowed by the magnetic suspension centrifugal compressor 1, which is particularly important for the emergency fault unloading shutdown, the shutdown safety and reliability of the magnetic suspension centrifugal compressor 1 can be improved, and the risk of bearing damage of the magnetic suspension centrifugal compressor 1 can be reduced.
In order to better understand the control method of the magnetic levitation air conditioning unit of the present invention, the detailed step flow of the control method is described in detail below with reference to the specific embodiment in fig. 3, and fig. 3 is a detailed step flow chart of the control method of the magnetic levitation air conditioning unit of the present invention.
Referring to fig. 3, the control method of the magnetic levitation air conditioning unit in the embodiment includes the following steps:
s10, when the magnetic suspension air conditioning unit meets the stop condition, acquiring the current pressure ratio of the magnetic suspension centrifugal compressor 1;
it should be noted that the magnetic suspension air conditioning unit meets the shutdown conditions including water temperature shutdown, active shutdown, unit alarm fault shutdown and the like.
In addition, when the magnetic suspension air conditioning unit comprises a plurality of magnetic suspension centrifugal compressors 1, namely a multi-handpiece magnetic suspension air conditioning unit in the field, the plurality of magnetic suspension centrifugal compressors 1 are arranged in parallel, the plurality of magnetic suspension centrifugal compressors 1 can be selectively started to work simultaneously according to the actual operating environment and different working conditions of the air conditioning unit, and part of the magnetic suspension centrifugal compressors 1 can be controlled to stop according to actual requirements, namely the handpiece reduction work generally referred by technical personnel in the field.
Further, the pressure ratio of the magnetic levitation centrifugal compressor 1 described herein refers to a suction-discharge absolute pressure ratio, which is a ratio of an outlet discharge pressure (absolute pressure) to an inlet suction pressure (absolute pressure) of the magnetic levitation centrifugal compressor 1. In general, the outlet discharge pressure of the magnetic suspension centrifugal compressor 1 is obtained by a pressure sensor arranged at the outlet, the inlet suction pressure of the magnetic suspension centrifugal compressor is obtained by a pressure sensor arranged at the inlet, and the two pressure sensors are in communication connection with a controller of the magnetic suspension air conditioning unit so as to transmit the collected discharge pressure and suction pressure to the controller, and a calculation module in the controller calculates the current pressure ratio. The allowable shutdown pressure ratio threshold value refers to a pressure ratio preset in a controller of the magnetic suspension air conditioning unit, and when the current pressure ratio of the magnetic suspension centrifugal compressor 1 is smaller than or equal to the allowable shutdown pressure ratio threshold value, the magnetic suspension centrifugal compressor 1 is directly controlled to be shut down, so that a bearing of the magnetic suspension centrifugal compressor is not damaged.
And S11, judging whether the current pressure ratio of the magnetic suspension centrifugal compressor 1 is larger than the threshold value of the allowable shutdown pressure ratio.
And executing the step S12 when the current pressure ratio of the magnetic suspension centrifugal compressor 1 is greater than the threshold value of the allowable shutdown pressure ratio, otherwise executing the step S16, namely executing the step S16 when the current pressure ratio of the magnetic suspension centrifugal compressor 1 is less than or equal to the threshold value of the allowable shutdown pressure ratio, and controlling the magnetic suspension centrifugal compressor 1 to be shutdown.
And S12, operating the magnetic suspension centrifugal compressor 1 in the current state for a preset time.
And S13, judging whether the current pressure ratio of the magnetic suspension centrifugal compressor 1 is larger than the threshold value of the allowable shutdown pressure ratio again.
If the current pressure ratio of the magnetic levitation centrifugal compressor 1 is still greater than the threshold value of the allowable shutdown pressure ratio after the second judgment, it indicates that the current pressure ratio of the magnetic levitation centrifugal compressor 1 is relatively constant and greater than the threshold value of the allowable shutdown pressure ratio and is not an instantaneous sudden fluctuation value, and then step S14 is executed to release pressure to the magnetic levitation centrifugal compressor 1.
And after the judgment again, if the current pressure ratio of the magnetic suspension centrifugal compressor 1 is less than or equal to the threshold value of the allowable shutdown pressure ratio, the current pressure ratio is only an instantaneous sudden fluctuation value, and then the magnetic suspension centrifugal compressor 1 is confirmed to enter the minimum capacity maintaining state. The minimum capacity maintaining state of the magnetic suspension centrifugal compressor 1 is that the minimum load which cannot surge of the magnetic suspension centrifugal compressor 1 is calculated in real time according to the operation state, so that the magnetic suspension centrifugal compressor 1 is assigned, namely the magnetic suspension centrifugal compressor 1 enters the minimum capacity maintaining state, the magnetic suspension centrifugal compressor 1 is operated at the lowest frequency, the operation pressure ratio is reduced, the magnetic suspension centrifugal compressor 1 is stopped conveniently, the magnetic suspension centrifugal compressor 1 cannot be damaged too much when the magnetic suspension centrifugal compressor 1 is stopped directly, and therefore the step S16 is executed to directly control the magnetic suspension centrifugal compressor 1 to stop.
It should be noted that, in step S12, the magnetic levitation centrifugal compressor 1 operates in the current state for a preset time period, where the specific time period is short, and is usually 1S (second) to 3S (second), and the specific value depends on performance parameters such as power of the magnetic levitation centrifugal compressor 1, and may be preset by a person skilled in the art according to actual conditions.
S14, opening the pressure relief switching element 71 and the pressure relief throttling element 70.
That is, in this embodiment, the pressure relief switch element 71 and the pressure relief throttling element 70 are simultaneously turned on, and the pressure relief effect can be rapidly achieved by simultaneously relieving the pressure.
In step S1, the opening degree of the pressure-releasing restriction element 70 is the maximum, that is, the opening degree of the pressure-releasing restriction element is 100%.
S15, judging whether the opening time of the pressure relief switch element 71 reaches a first preset time.
The setting of the first preset time period is adjusted according to the test time situation, the adjustment principle is that the pressure ratio is obviously reduced in the first preset time period, and the pressure ratio is relatively slowly reduced after the first preset time period is exceeded, and the adjustment principle can be set by a person skilled in the art according to the adjustment principle. For example, the first preset time period may be preferably 2s (seconds).
If the opening time of the pressure relief switch element 71 reaches the first preset time, no matter the current pressure ratio of the magnetic suspension centrifugal compressor 1 is less than or equal to the allowable shutdown pressure ratio threshold, step S16 is executed, that is, the magnetic suspension centrifugal compressor 1 is directly controlled to be shutdown.
If the opening time of the pressure release switch element 71 does not reach the first preset time, the process returns to step S13.
With continued reference to fig. 3, after the step S16 controls the magnetic levitation centrifugal compressor 1 to stop, the control method of the present embodiment does not directly close the pressure relief switch element 71, but continues to perform the step S17.
S17, the step S18 is executed after the pressure relief switch element 71 is kept open for the second preset time.
S18, the pressure-release switch element 71 is turned off.
The step S17 is set in the control method of this embodiment, so that the magnetic levitation centrifugal compressor 1 stops, because the magnetic levitation centrifugal compressor 1 and the PLC directly have communication time, and there is also confirmation of response inside the magnetic levitation centrifugal compressor 1, that is, the magnetic levitation centrifugal compressor 1 can execute the stop after the controller sends the stop command of the magnetic levitation centrifugal compressor 1 and delays for a certain time. Therefore, in the control method of the embodiment, after the magnetic levitation centrifugal compressor 1 is controlled to stop, the pressure relief switch element 71 is turned off after a second preset time delay, so as to compensate the lag time of the magnetic levitation centrifugal compressor 1 responding to the stop action, and ensure that the pressure relief switch element 71 is turned off after the magnetic levitation centrifugal compressor 1 actually stops.
As described above, the maglev air conditioning unit of the present embodiment includes, in addition to the indispensable functional elements of the maglev centrifugal compressor 1, the condenser 2, the main path throttling element 4 and the evaporator 3, other auxiliary elements, and the names, connection relationships and functions of these auxiliary elements with other main functional elements will be described in detail below with reference to fig. 1.
With continued reference to fig. 1, the maglev air conditioning unit of the present embodiment further includes an economizer 5 and an economizer-side throttling element 51. Wherein, two parallelly connected two way refrigerant runners that set up have in the economizer 5, first refrigerant runner and second refrigerant runner promptly: the refrigerant inlet 5a of the first refrigerant channel is communicated with the refrigerant outlet of the condenser 2 through a drying filter 6, and the refrigerant outlet 5c of the first refrigerant channel is communicated with the refrigerant inlet of the evaporator 3 through a main path throttling element 4; the refrigerant inlet 5b of the second refrigerant flow path and the dry filter 6 are communicated through an economizer-side throttling element 51 connected in series to the parallel branch, and the refrigerant outlet 5d of the second refrigerant flow path and the cooling port of the magnetic levitation centrifugal compressor 1 are communicated through an economizer-side temperature sensor 53 and an economizer-side pressure sensor 52 connected in series.
The purpose of additionally arranging the cooling branch bypass is to divide a refrigerant from the condenser 2 into two paths, wherein one path still belongs to a main circulation loop, enters a main path throttling element 4 for throttling and pressure reduction after drying and filtering treatment, and then enters the evaporator 3, and the other path forms a cooling bypass, namely, directly enters the magnetic suspension centrifugal compressor 1 through a cooling port of the magnetic suspension centrifugal compressor 1 for cooling functional elements in the magnetic suspension centrifugal compressor 1 after being throttled and pressure reduced by an economizer side throttling element 51.
The amount of refrigerant entering the magnetic levitation centrifugal compressor 1 from the cooling bypass depends on the opening of the economizer-side throttling element 51, the opening of the economizer-side throttling element 51 is determined by the temperature and pressure at the cooling port of the magnetic levitation centrifugal compressor 1, and the temperature and pressure at the cooling port of the magnetic levitation centrifugal compressor 1 are collected by an economizer-side pressure sensor and an economizer-side temperature sensor and transmitted to the controller of the air conditioning unit.
With continuing reference to fig. 1, the magnetic levitation air conditioning unit of the present embodiment further includes another cooling bypass, where the cooling bypass includes a cooling switching element 90 and a cooling filter 91 connected in series, a liquid cooling port of the magnetic levitation centrifugal compressor 1 is communicated with the condenser 2 through the cooling bypass, and when the cooling switching element 90 is turned on, functional elements in the magnetic levitation centrifugal compressor 1 can be cooled by using a liquid refrigerant in the condenser 2.
With continued reference to fig. 1, the magnetically levitated air conditioning assembly further comprises a one-way conduction bypass which one-way conducts the air outlet of the magnetically levitated centrifugal compressor 1 and the refrigerant inlet of the condenser 2, preferably the one-way conduction bypass comprises a one-way valve 8, the one-way valve 8 allowing the refrigerant to flow from the refrigerant outlet of the magnetically levitated centrifugal compressor 1 to the refrigerant inlet of the condenser 2.
After the one-way conduction bypass is arranged, in the shutdown operation stage of the magnetic suspension centrifugal compressor 1, after the pressure relief switch element 71 and the pressure relief throttling element 70 are opened for pressure relief, the one-way valve 8 can prevent the problem that the refrigerant flows back from the condenser 2 to the magnetic suspension centrifugal compressor 1 due to the sharp reduction of the pressure ratio, so that the working safety of the air conditioning unit is ensured.
It should be noted that, in the embodiment, the water-cooling magnetic suspension air conditioning unit is taken as an example to describe the control method of the present invention, and it can be understood that the control method of the present invention is also applicable to the air-cooling magnetic suspension air conditioning unit, that is, the condenser 2 is the air-cooling condenser 2, and is also applicable to the evaporation cooling magnetic suspension air conditioning unit, that is, the condenser 2 is the evaporation cooling condenser 2.
Finally, it should be emphasized that the main throttle element 4, the pressure relief throttle element 70 and the economizer side throttle element 51 in this embodiment are all electronic expansion valves, and these throttle elements may be other throttle elements such as thermal expansion valves and the like on the basis of satisfying the throttling and pressure reducing functions. The pressure relief switching element 71 is preferably an electromagnetic switching valve.
So far, the technical solutions of the present invention have been described in connection with the preferred embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of the present invention is obviously not limited to these specific embodiments. Equivalent changes or substitutions of related technical features can be made by those skilled in the art without departing from the principle of the invention, and the technical scheme after the changes or substitutions can fall into the protection scope of the invention.
Claims (10)
1. A control method of a magnetic suspension air conditioning unit comprises a pressure relief bypass for relieving pressure of a magnetic suspension centrifugal compressor, and is characterized in that the pressure relief bypass comprises a pressure relief switch valve and a pressure relief throttling element which are arranged in parallel, and the control method comprises the following steps:
when the magnetic suspension air conditioning unit meets a shutdown condition, acquiring the current pressure ratio of the magnetic suspension centrifugal compressor;
comparing the magnitude relationship between the current pressure ratio and a threshold allowable shutdown pressure ratio;
and selectively and directly controlling the magnetic suspension centrifugal compressor to stop or starting the pressure relief switch valve and the pressure relief throttling element to adjust the pressure ratio until the condition that the magnetic suspension centrifugal compressor stops is reached according to the comparison result.
2. The control method according to claim 1, wherein the step of selectively and directly controlling the magnetic suspension centrifugal compressor to stop or opening the pressure relief switch valve and the pressure relief throttling element to adjust the pressure ratio until reaching the condition of stopping the magnetic suspension centrifugal compressor according to the comparison result comprises the following steps:
and when the current pressure ratio is smaller than or equal to the allowable shutdown pressure ratio threshold value, directly controlling the magnetic suspension centrifugal compressor to be shut down.
3. The control method according to claim 1, wherein the step of selectively and directly controlling the magnetic suspension centrifugal compressor to stop or opening the pressure relief switch valve and the pressure relief throttling element to adjust the pressure ratio until reaching the condition of stopping the magnetic suspension centrifugal compressor according to the comparison result comprises the following steps:
and when the current pressure ratio is greater than the threshold value of the allowable shutdown pressure ratio, opening the pressure relief switch valve and the pressure relief throttling element to adjust the pressure ratio until the shutdown condition of the magnetic suspension centrifugal compressor is reached.
4. The control method according to claim 3, characterized in that when the current pressure ratio is greater than the permissible shutdown pressure ratio threshold, the control method further comprises the steps of:
keeping the magnetic suspension centrifugal compressor to operate in the current state for a preset time;
comparing the magnitude relation between the current pressure ratio of the magnetic suspension centrifugal compressor and the allowable shutdown pressure ratio threshold value again;
and selectively and directly controlling the magnetic suspension centrifugal compressor to stop according to the result of the comparison again, or opening the pressure relief switch valve and the pressure relief throttling element to adjust the pressure ratio until the condition that the magnetic suspension centrifugal compressor stops is reached.
5. The control method according to claim 4, wherein selectively controlling the magnetically levitated centrifugal compressor to stop directly or opening the pressure relief switch valve and the pressure relief throttling element to adjust the pressure ratio until a condition for stopping the magnetically levitated centrifugal compressor is reached according to the result of the comparison again comprises the following steps:
and when the result of the comparison again shows that the current pressure ratio is greater than the threshold value of the allowable shutdown pressure ratio, opening the pressure relief switch valve and the pressure relief throttling element to adjust the pressure ratio until the shutdown condition of the magnetic suspension centrifugal compressor is reached.
6. The control method according to claim 4, wherein selectively controlling the magnetically levitated centrifugal compressor to stop directly or opening the pressure relief switch valve and the pressure relief throttling element to adjust the pressure ratio until a condition for stopping the magnetically levitated centrifugal compressor is reached according to the result of the comparison again comprises the following steps:
and when the current pressure ratio is smaller than or equal to the allowable stop pressure ratio threshold value as a result of the comparison again, directly controlling the magnetic suspension centrifugal compressor to stop.
7. The control method according to any one of claims 4 to 6, wherein the method for judging whether the condition for stopping the magnetic levitation centrifugal compressor is reached in the step of opening the pressure relief switch valve and the pressure relief throttling element to adjust the pressure ratio until the condition for stopping the magnetic levitation centrifugal compressor is reached comprises the steps of:
judging whether the opening time of the pressure relief switch valve reaches a first preset time;
if yes, indicating that the magnetic suspension centrifugal compressor is stopped, and controlling the magnetic suspension centrifugal compressor to stop;
otherwise, returning to the step of comparing the magnitude relation between the current pressure ratio of the magnetic suspension centrifugal compressor and the allowable stop pressure ratio threshold again.
8. The control method according to any one of claims 1 to 6, characterized in that, after controlling the compressor to stop, the control method further comprises the steps of:
keeping the opening of the pressure relief switch valve for a second preset time;
and closing the pressure relief switch valve.
9. The control method according to any one of claims 1 to 6, wherein the magnetic levitation air conditioning unit further comprises a one-way conduction bypass for allowing a refrigerant to flow from an exhaust port of the compressor to a refrigerant inlet of the condenser in a one-way direction.
10. The control method according to claim 9, wherein the one-way communication bypass includes a one-way valve, and the discharge port of the compressor and the refrigerant inlet of the condenser are communicated through the one-way valve, and the one-way valve allows a one-way flow of the refrigerant from the discharge port of the compressor to the refrigerant inlet of the condenser.
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| CN117588491A (en) * | 2024-01-18 | 2024-02-23 | 瑞纳智能设备股份有限公司 | Magnetic suspension bearing system, shutdown control method and device thereof and electrical equipment |
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Application publication date: 20210720 |