Heat pump unit and control method thereof

Abstract

The application provides a heat pump unit and a control method thereof. The heat pump unit comprises a first compression device and a second compression device, a first air supplement device, a second air supplement device and a third air supplement device. The first compression device comprises a first cylinder, an intermediate cavity and a second cylinder. Exhaust gas of the first cylinder enters the intermediate cavity, and exhaust gas of the intermediate cavity enters the second cylinder, forming at least two-stage compression. Exhaust gas of the first compression device enters a suction port of the second compression device. The first air supplement device supplements air for at least one of the first cylinder, the intermediate cavity and the second cylinder. The second air supplement device and the third air supplement device both supplement air for the second compression device. The first air supplement device controls air supplement for the first cylinder, the intermediate cavity and the second cylinder according to exhaust gas temperature of the first compression device. The second air supplement device and the third air supplement device both control air supplement for the second compression device according to exhaust gas temperature of the second compression device. The application can solve the problem of low heating capacity at low temperature in the prior art.

Description

Technical Field

[0001] This invention relates to the field of heat pump technology, and more specifically to a heat pump unit and its control method. Background Technology

[0002] With the increasing popularity of heat pump water heaters in the context of coal-to-electricity conversion, their application scenarios are becoming more and more widespread. The heating process of a heat pump water heater mainly involves absorbing heat from the outdoor air. Through the work of the compressor, heat is absorbed from the low-temperature heat source, i.e., the air, on the evaporator side. Then, through a water system heat exchanger, such as a plate heat exchanger or a shell-and-tube heat exchanger, the heat in the high-temperature refrigerant is transferred to the water system, circulating through the water circuit to provide heating to users. In northern regions, the lower the temperature, the greater the demand for heating. As the temperature decreases, evaporation also decreases. If the outlet water temperature remains constant, i.e., the condensing pressure remains constant, the compressor's compression ratio (condensing pressure / evaporating pressure) will increase. An excessively high compression ratio reduces the intake air volume, lowers the capacity, and increases the exhaust temperature, leading to reliability issues. However, at low temperatures, the demand for heat increases, and the heating capacity of the heat pump decreases as the temperature drops. This creates a supply-demand imbalance, limiting the application of heat pumps.

[0003] Because existing heat pump units suffer from technical problems such as low heating capacity at low temperatures, this invention studies and designs a heat pump unit and its control method. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defect of low heating capacity at low temperatures in the heat pump units of the prior art, thereby providing a heat pump unit and its control method.

[0005] To address the above problems, the present invention provides a heat pump unit, comprising:

[0006] The system comprises a first compression device, a second compression device, a first air supply device, a second air supply device, and a third air supply device. The first compression device includes a first cylinder, an intermediate chamber, and a second cylinder. The exhaust gas from the first cylinder enters the intermediate chamber, and the exhaust gas from the intermediate chamber enters the second cylinder, forming at least two stages of compression. The exhaust gas from the first compression device enters the intake port of the second compression device.

[0007] The first air supply device can supply air to at least one of the first cylinder, the intermediate chamber, and the second cylinder. The second air supply device and the third air supply device can both supply air to the second compression device. The first air supply device can control the air supply to the first cylinder, the intermediate chamber, and the second cylinder according to the exhaust temperature of the first compression device. The second air supply device and the third air supply device can both control the air supply to the second compression device according to the exhaust temperature of the second compression device.

[0008] In some implementations...

[0009] The first air supply device is connected to the air supply port of the first cylinder through a first air supply pipeline, and a first valve is provided on the first air supply pipeline. The first air supply device is connected to the air supply port of the intermediate cavity through a second air supply pipeline, and a second valve is provided on the second air supply pipeline. The first air supply device is connected to the air supply port of the second cylinder through a third air supply pipeline, and a third valve is provided on the third air supply pipeline.

[0010] The outlet of the second cylinder is connected to the intake port of the second compression device through the first pipeline. A first temperature detection device is provided on the first pipeline. The first valve, the second valve, and the third valve are all control valves. The first valve, the second valve, and the third valve are all controlled to open and close according to the exhaust temperature detected by the first temperature detection device.

[0011] In some implementations...

[0012] The first air supply device can also supply air to the intake port of the second compression device, and the first air supply device can control the supply of air to the second compression device according to the exhaust temperature of the second compression device;

[0013] The first air supply device is connected to the air intake of the second compression device through a fourth air supply pipeline, and a fourth valve is provided on the fourth air supply pipeline; the second air supply device is connected to the air intake of the second compression device through a fifth air supply pipeline, and a fifth valve is provided on the fifth air supply pipeline.

[0014] The exhaust port of the second compression device exhausts gas through the second pipeline. The second pipeline is equipped with a second temperature detection device. The fourth valve and the fifth valve are both control valves. The fourth valve and the fifth valve are controlled to open and close according to the exhaust temperature detected by the second temperature detection device.

[0015] In some implementations...

[0016] The third air replenishment device is connected to the intake port of the second compression device through a sixth air replenishment pipeline, and a sixth valve is provided on the sixth air replenishment pipeline; the sixth valve is a control valve; the sixth valve is opened and closed according to the exhaust temperature detected by the second temperature detection device; the third air replenishment device is also connected to the air replenishment port of the second compression device through a seventh air replenishment pipeline, and a seventh valve is provided on the seventh air replenishment pipeline, the seventh valve is a control valve; the seventh valve is opened and closed according to the exhaust temperature detected by the second temperature detection device.

[0017] In some implementations...

[0018] The second air replenishment device is connected to the air intake of the second compression device through a fourth air replenishment pipeline, and a fourth valve is provided on the fourth air replenishment pipeline; the third air replenishment device is connected to the air intake of the second compression device through a fifth air replenishment pipeline, and a fifth valve is provided on the fifth air replenishment pipeline; the third air replenishment device is also connected to the air replenishment port of the second compression device through a sixth air replenishment pipeline, and a sixth valve is provided on the sixth air replenishment pipeline.

[0019] The exhaust port of the second compression device exhausts gas through the second pipeline. The second pipeline is equipped with a second temperature detection device. The fourth valve, the fifth valve, and the sixth valve are all control valves. The fourth valve, the fifth valve, and the sixth valve are all controlled to open and close according to the exhaust temperature detected by the second temperature detection device.

[0020] In some implementations...

[0021] It also includes a first heat exchanger, a second heat exchanger, a first throttling device, a second throttling device, a third throttling device, a third pipeline, a fourth pipeline, a fifth pipeline, and a tenth pipeline. The first gas supply device is connected to one end of the first heat exchanger through the third pipeline, and the first throttling device is installed on the third pipeline. The second gas supply device is connected to the first gas supply device through the fourth pipeline, and the second throttling device is installed on the fourth pipeline. The second gas supply device is connected to the third gas supply device through the fifth pipeline, and the third throttling device is installed on the fifth pipeline. The third gas supply device is connected to one end of the second heat exchanger through the tenth pipeline, and the fourth throttling device is installed on the tenth pipeline.

[0022] In some implementations...

[0023] It also includes a four-way valve, a gas-liquid separator, a sixth pipeline, a seventh pipeline, an eighth pipeline, and a ninth pipeline. The outlet of the second compression device is connected to the first end of the four-way valve through the second pipeline. The first heat exchanger is connected to the second end of the four-way valve through the sixth pipeline. The second heat exchanger is connected to the third end of the four-way valve through the seventh pipeline. The gas-liquid separator is connected to the fourth end of the four-way valve through the eighth pipeline. The gas-liquid separator is also connected to the intake port of the first compression device through the ninth pipeline.

[0024] The present invention also provides a control method for a heat pump unit as described above, comprising:

[0025] The detection step involves detecting the exhaust temperature T1 of the first compression device using the first temperature detection device.

[0026] The judgment step is to determine the relationship between T1 and the first preset temperature a;

[0027] Control step: when T1≥a, open the first valve and supply air through the air inlet of the first cylinder; when T1 < a - x, close the first valve and do not supply air; when a - x ≤ T1 < a, the first valve maintains its original state; where x is a constant.

[0028] In some embodiments,

[0029] The judging step also judges the relationship between T1 and the second preset temperature b, where b > a;

[0030] In the control step: when T1≥b, open the first valve and the second valve, and supply air simultaneously through the air inlet of the first cylinder and the air inlet of the intermediate cavity; when T1 < b - x, open the first valve and close the second valve; when b - x ≤ T1 < b, the first valve and the second valve maintain their original states, and at this time b - x ≥ a.

[0031] In some embodiments,

[0032] The judging step also judges the relationship between T1 and the third preset temperature c, where c > b;

[0033] In the control step: when T1≥c, open the first valve, the second valve and the third valve simultaneously, and supply air simultaneously through the air inlet of the first cylinder, the air inlet of the intermediate cavity and the air inlet of the second cylinder; when T1 < c - x, open the first valve and the second valve, and close the third valve; when c - x ≤ T1 < c, the first valve, the second valve and the third valve maintain their original states, and at this time c - x ≥ b.

[0034] In some embodiments,

[0035] The detecting step also detects the exhaust temperature T2 of the second compression device through the second temperature detecting device;

[0036] The judging step judges the relationship between T2 and the fourth preset temperature d;

[0037] In the control step: when T2≥d, open the fourth valve and supply air through the air inlet of the second compression device; when T2 < d - y, close the fourth valve; when d - y ≤ T2 < d, the first valve, the second valve, the third valve and the fourth valve all maintain their original states; where y is a constant.

[0038] In some embodiments,

[0039] The judging step judges the relationship between T2 and the fifth preset temperature e, where e > d;

[0040] In the control step, when T2 ≥ e, open the fifth valve, close the fourth valve, and supplement air through the suction port of the second compression device; when T2 < e - y, close the fifth valve and open the fourth valve; when e - y ≤ T2 < e, the first valve, the second valve, the third valve, the fourth valve, and the fifth valve all maintain their original states, and at this time e - y ≥ d.

[0041] In some embodiments,

[0042] In the determination step, determine the relationship between T2 and the sixth preset temperature f, where f > e;

[0043] In the control step, when T2 ≥ f, open the sixth valve, close the fourth valve and the fifth valve, and supplement air through the suction port of the second compression device; when it is detected that T2 < f - y, open the fifth valve, close the sixth valve and the fourth valve; when f - y ≤ T2 < f, the first valve, the second valve, the third valve, the fourth valve, the fifth valve, and the sixth valve all maintain their original states, and at this time f - y ≥ e.

[0044] In some embodiments,

[0045] In the determination step, determine the relationship between T2 and the seventh preset temperature g, where g > f;

[0046] In the control step, when T2 ≥ g, open the fifth valve and the seventh valve, close the fourth valve and the sixth valve, and supplement air through the suction port and the air supplement port of the second compression device; when it is detected that T2 < g - y, open the sixth valve, close the fifth valve, the seventh valve, and the fourth valve; when g - y ≤ T2 < g, the first valve, the second valve, the third valve, the fourth valve, the fifth valve, the sixth valve, and the seventh valve all maintain their original states, and at this time g - y ≥ f.

[0047] In some embodiments,

[0048] In the determination step, determine the relationship between T2 and the eighth preset temperature h, where h > g;

[0049] In the control step, when T2 ≥ h, open the sixth valve and the seventh valve, close the fourth valve and the fifth valve, and supplement air through the suction port and the air supplement port of the second compression device; when it is detected that T2 < h - y, open the fifth valve, close the sixth valve, the seventh valve, and the fourth valve; when h - y ≤ T2 < h, the first valve, the second valve, the third valve, the fourth valve, the fifth valve, the sixth valve, and the seventh valve all maintain their original states, and at this time g - y ≥ f.

[0050] The heat pump unit and its control method provided by this invention have the following beneficial effects:

[0051] 1. This invention employs two series-connected compression devices, with the first compression device having at least two cylinders, and a first air supply device capable of supplying air to at least one of the first, second, and intermediate cylinders. This effectively increases the air supply volume, particularly improving the air supply volume of the compressor under low-temperature or ultra-low-temperature conditions, thereby enhancing heating capacity. Furthermore, the first air supply device can control the air supply to the first cylinder, the intermediate cylinder, and the second cylinder based on the exhaust temperature of the first compression device, while the second and third air supply devices can control the air supply to the second compression device based on its exhaust temperature. This allows for selective air supply to one or more cylinder positions based on the exhaust temperature of the first compression device, and selective air supply to the second compression device based on its exhaust temperature. Selectively supplementing gas at multiple locations in the second compression unit creates a reasonable gas supplementation control scheme. This allows both the first and second compression units to have their exhaust temperatures reduced to a specified range, improving temperature control accuracy and ensuring that the exhaust temperature does not become too high. This prevents exhaust protection shutdowns and avoids wear and tear. Simultaneously, it increases the amount of gas supplied to the compression units, thereby enhancing heating / cooling capacity and increasing outlet water temperature. This effectively solves the problem of high compressor pressure ratios in ultra-low temperature environments failing to meet high outlet water temperatures, effectively improving the outlet water temperature. It also effectively addresses the issue of low heating capacity at low temperatures in existing heat pump units, while simultaneously resolving the problem of excessively high exhaust temperatures, ensuring precise exhaust temperature control and preventing protection shutdowns.

[0052] 2. The present invention further provides that the first air replenishment device can be connected to the intake port of the second compression device via a fourth air replenishment pipeline, the fourth air replenishment pipeline being equipped with a fourth valve. The second air replenishment device is also connected to the intake port of the second compression device via a fifth air replenishment pipeline, the fifth air replenishment pipeline being equipped with a fifth valve. The exhaust port of the second compression device exhausts gas through a second pipeline, the second pipeline being equipped with a second temperature detection device. Both the fourth and fifth valves are control valves, and both are opened and closed according to the exhaust temperature detected by the second temperature detection device; this enables the first and second... The air replenishment device also selectively replenishes air to the intake port of the second compressor based on the exhaust temperature of the second compressor, forming a reasonable air replenishment control scheme. This allows the exhaust temperature of the second compressor to be reduced to a specified temperature range, improving temperature control accuracy and ensuring that the exhaust temperature is not too high. This further avoids shutdown due to exhaust protection of the second compressor and prevents wear and tear. At the same time, it can further increase the amount of air replenished to the second compressor, thereby improving the heating / cooling capacity and the outlet water temperature. This effectively solves the problem that the compressor pressure ratio is too large to meet the high outlet water temperature in ultra-low temperature environments, and effectively improves the outlet water temperature.

[0053] 3. The present invention further includes a third air supply device connected to the intake port of the second compression device via a sixth air supply pipeline. The sixth air supply pipeline is equipped with a sixth valve, which is a control valve. The sixth valve opens and closes according to the exhaust temperature detected by the second temperature detection device. Additionally, the third air supply device is connected to the air supply port of the second compression device via a seventh air supply pipeline. The seventh air supply pipeline is equipped with a seventh valve, which is also a control valve. The seventh valve opens and closes according to the exhaust temperature detected by the second temperature detection device. This allows the third air supply device to adjust its operation based on the exhaust temperature detected by the second temperature detection device. The exhaust temperature of the second compressor is controlled by selectively supplying air to its intake and replenishment ports, forming a reasonable air supply control scheme. This further reduces the exhaust temperature of the second compressor to a specified range, improving temperature control accuracy and ensuring that the exhaust temperature does not become too high. This prevents the second compressor from shutting down due to exhaust protection and avoids wear and tear. At the same time, it increases the amount of air supplied to the second compressor, thereby improving heating / cooling capacity and increasing the outlet water temperature. This effectively solves the problem of the compressor's high pressure ratio being unable to meet the high outlet water temperature requirement in ultra-low temperature environments, and effectively improves the outlet water temperature. Attached Figure Description

[0054] Figure 1 This is a system structure diagram of the heat pump unit in the main embodiment of the present invention;

[0055] Figure 2This is a system structure diagram of a heat pump unit according to an alternative embodiment of the present invention.

[0056] The reference numerals in the attached figures are as follows:

[0057] 1. First compression device; 11. First cylinder; 12. Intermediate chamber; 13. Second cylinder; 2. Second compression device; 3. One-way valve; 4. First air supply device; 5. Second air supply device; 6. Second heat exchanger; 7. Four-way valve; 8. First heat exchanger; 9. Gas-liquid separator; 10. Third air supply device; 101. First air supply pipeline; 102. Second air supply pipeline; 103. Third air supply pipeline; 104. Fourth air supply pipeline; 105. Fifth air supply pipeline; 106. Sixth air supply pipeline; 107. Seventh air supply pipeline; 201. First pipeline; 20 2. Second pipeline; 203. Third pipeline; 204. Fourth pipeline; 205. Fifth pipeline; 206. Sixth pipeline; 207. Seventh pipeline; 208. Eighth pipeline; 209. Ninth pipeline; 210. Tenth pipeline; V1. First valve; V2. Second valve; V3. Third valve; V4. Fourth valve; V5. Fifth valve; V6. Sixth valve; V7. Seventh valve; E1. First throttling device; E2. Second throttling device; E3. Third throttling device; E4. Fourth throttling device; F1. First temperature detection device; F2. Second temperature detection device. Detailed Implementation

[0058] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0059] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0060] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. 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 figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0061] In the description of this invention, 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 generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention 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 invention; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0062] 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.

[0063] 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, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0064] like Figure 1-2As shown, the present invention provides a heat pump unit, which includes:

[0065] The system comprises a first compression device 1, a second compression device 2, a first air supply device 4, a second air supply device 5, and a third air supply device 10. The first compression device 1 includes a first cylinder 11, an intermediate chamber 12, and a second cylinder 13. The exhaust gas from the first cylinder 11 enters the intermediate chamber 12, and the exhaust gas from the intermediate chamber 12 enters the second cylinder 13, forming at least two-stage compression. The exhaust gas from the first compression device 1 enters the intake port of the second compression device 2.

[0066] The first air supply device 4 can supply air to at least one of the first cylinder 11, the intermediate chamber 12 and the second cylinder 13. The second air supply device 5 and the third air supply device 10 can both supply air to the second compression device 2. The first air supply device 4 can control the air supply to the first cylinder 11, the intermediate chamber 12 and the second cylinder 13 according to the exhaust temperature of the first compression device 1. The second air supply device 5 and the third air supply device 10 can both control the air supply to the second compression device 2 according to the exhaust temperature of the second compression device 2.

[0067] This invention employs two compressor units connected in series, with the first compressor unit having at least two cylinders, and a first air supply device capable of supplying air to at least one of the first, second, and intermediate cylinders. This effectively increases the air supply volume, particularly improving the air supply volume of the compressor under low-temperature or ultra-low-temperature conditions, thereby enhancing heating capacity. Furthermore, the first air supply device can control the air supply to the first cylinder, the intermediate cylinder, and the second cylinder based on the exhaust temperature of the first compressor unit, while the second and third air supply devices can control the air supply to the second compressor unit based on its exhaust temperature. This allows for selective air supply to one or more cylinder positions based on the exhaust temperature of the first compressor unit, and selective air supply to the second compressor unit based on its exhaust temperature. Selectively supplementing gas at multiple locations in the second compression unit creates a reasonable gas supplementation control scheme. This allows both the first and second compression units to have their exhaust temperatures reduced to a specified range, improving temperature control accuracy and ensuring that the exhaust temperature does not become too high. This prevents exhaust protection shutdowns and avoids wear and tear. Simultaneously, it increases the amount of gas supplied to the compression units, thereby enhancing heating / cooling capacity and increasing outlet water temperature. This effectively solves the problem of high compressor pressure ratios in ultra-low temperature environments failing to meet high outlet water temperatures, effectively improving the outlet water temperature. It also effectively addresses the issue of low heating capacity at low temperatures in existing heat pump units, while simultaneously resolving the problem of excessively high exhaust temperatures, ensuring precise exhaust temperature control and preventing protection shutdowns.

[0068] In some implementations...

[0069] The first air supply device 4 is connected to the air supply port of the first cylinder 11 through the first air supply pipeline 101, and a first valve V1 is provided on the first air supply pipeline 101. The first air supply device 4 is connected to the air supply port of the intermediate cavity 12 through the second air supply pipeline 102, and a second valve V2 is provided on the second air supply pipeline 102. The first air supply device 4 is connected to the air supply port of the second cylinder 13 through the third air supply pipeline 103, and a third valve V3 is provided on the third air supply pipeline 103.

[0070] The outlet of the second cylinder 13 is connected to the intake of the second compression device 2 through the first pipeline 201. A first temperature detection device F1 is provided on the first pipeline 201. The first valve V1, the second valve V2 and the third valve V3 are all control valves (preferably solenoid valves). The first valve V1, the second valve V2 and the third valve V3 are all controlled to open and close according to the exhaust temperature detected by the first temperature detection device F1.

[0071] This is a preferred system structure of the present invention, wherein a first air supply device and a first air supply pipeline are connected to the air supply port of the first cylinder to supply air to the first cylinder of the first compression device; the first air supply device and the second air supply pipeline are connected to the air supply port of the intermediate cavity to supply air to the intermediate cavity of the first compression device; and the first air supply device and the third air supply pipeline are connected to the air supply port of the second cylinder to supply air to the second cylinder of the first compression device. This allows for control of the opening and closing of the three air supply pipelines based on the exhaust temperature of the first compression device, ensuring that the exhaust temperature of the first compression device is not too high and that precise temperature control is achieved within a specified range, while also increasing or decreasing the air supply volume to meet the demand. Simultaneously, it ensures that the heating / cooling capacity of the heat exchanger in the system is maximized (ensuring the exhaust temperature is within a specified range while simultaneously improving the cooling / heating capacity), thus improving the energy efficiency of the heat pump system.

[0072] Main embodiment, such as Figure 1 In some implementation methods,

[0073] The first air supply device 4 can also supply air to the air intake and air supply ports of the second compression device 2. The first air supply device 4 can control the air supply to the second compression device 2 according to the exhaust temperature of the second compression device 2.

[0074] The first air supply device 4 is connected to the air intake of the second compression device 2 through the fourth air supply pipeline 104, and the fourth air supply pipeline 104 is provided with a fourth valve V4; the second air supply device 5 is connected to the air intake of the second compression device 2 through the fifth air supply pipeline 105, and the fifth air supply pipeline 105 is provided with a fifth valve V5.

[0075] The exhaust port of the second compression device 2 exhausts through the second pipeline 202. The second pipeline 202 is equipped with a second temperature detection device F2. The fourth valve V4 and the fifth valve V5 are both control valves. The fourth valve V4 and the fifth valve V5 are controlled to open and close according to the exhaust temperature detected by the second temperature detection device F2.

[0076] This is a preferred system structure of the present invention, wherein the first air supply device is further connected to the intake port of the second compression device via a fourth air supply pipeline, the fourth air supply pipeline being equipped with a fourth valve. The second air supply device is also connected to the intake port of the second compression device via a fifth air supply pipeline, the fifth air supply pipeline being equipped with a fifth valve. The exhaust port of the second compression device exhausts gas through a second pipeline, the second pipeline being equipped with a second temperature detection device. Both the fourth and fifth valves are control valves, and both the fourth and fifth valves are opened and closed according to the exhaust temperature detected by the second temperature detection device; enabling... The first and second air replenishment devices also selectively replenish air to the intake port of the second compressor based on the exhaust temperature of the second compressor, forming a reasonable air replenishment control scheme. This allows the exhaust temperature of the second compressor to be reduced to a specified temperature range, improving temperature control accuracy and ensuring that the exhaust temperature is not too high. This further avoids shutdown due to exhaust protection of the second compressor and prevents wear and tear. At the same time, it can further increase the amount of air replenished to the second compressor, thereby improving the heating / cooling capacity and the outlet water temperature. This effectively solves the problem that the compressor pressure ratio is too large to meet the high outlet water temperature in ultra-low temperature environments, and effectively improves the outlet water temperature.

[0077] This invention enables the increase or decrease of the gas supply volume while ensuring that the exhaust temperature of the second compression device is not too high and that precise temperature control is achieved within a specified range. This ensures that the gas supply volume meets the requirements and that the heating / cooling capacity of the heat exchanger in the system is maximized (ensuring that the exhaust temperature is within a specified range while also improving the cooling / heating capacity), thereby improving the energy efficiency of the heat pump system.

[0078] In some implementations...

[0079] The third air replenishment device 10 is connected to the intake port of the second compression device 2 via a sixth air replenishment pipeline 106. A sixth valve V6 is provided on the sixth air replenishment pipeline 106. The sixth valve V6 is a control valve. The sixth valve V6 is opened and closed according to the exhaust temperature detected by the second temperature detection device F2. The third air replenishment device 10 is also connected to the air replenishment port of the second compression device 2 via a seventh air replenishment pipeline 107. A seventh valve V7 is provided on the seventh air replenishment pipeline 107. The seventh valve V7 is a control valve. The seventh valve V7 is opened and closed according to the exhaust temperature detected by the second temperature detection device F2.

[0080] The present invention further connects the third air supply device to the intake port of the second compression device via a sixth air supply pipeline. The sixth air supply pipeline is equipped with a sixth valve, which is a control valve. The sixth valve is opened and closed based on the exhaust temperature detected by the second temperature detection device. Additionally, the third air supply device is also connected to the intake port of the second compression device via a seventh air supply pipeline. The seventh air supply pipeline is equipped with a seventh valve, which is a control valve. The seventh valve is also opened and closed based on the exhaust temperature detected by the second temperature detection device. This allows the third air supply device to operate according to the exhaust temperature detected by the second temperature detection device. The exhaust temperature of the compressor unit is controlled to selectively replenish the intake and replenishment ports of the second compressor unit, forming a reasonable replenishment control scheme. This further reduces the exhaust temperature of the second compressor unit to a specified temperature range, improving temperature control accuracy and ensuring that the exhaust temperature does not become too high. This further avoids shutdown due to exhaust protection of the second compressor unit and prevents wear and tear. At the same time, it can also increase the replenishment amount to the second compressor unit, thereby improving heating / cooling capacity and increasing the outlet water temperature. This effectively solves the problem that the compressor pressure ratio is too large to meet the high outlet water temperature in ultra-low temperature environments, and effectively improves the outlet water temperature.

[0081] Alternative embodiments, such as Figure 2 In some implementation methods,

[0082] The second air supply device 5 is connected to the air intake of the second compression device 2 through the fourth air supply pipeline 104, and the fourth air supply pipeline 104 is provided with a fourth valve V4; the third air supply device 10 is connected to the air intake of the second compression device 2 through the fifth air supply pipeline 105, and the fifth air supply pipeline 105 is provided with a fifth valve V5; the third air supply device 10 is also connected to the air supply port of the second compression device 2 through the sixth air supply pipeline 106, and the sixth air supply pipeline 106 is provided with a sixth valve V6;

[0083] The exhaust port of the second compression device 2 exhausts gas through the second pipeline 202. The second pipeline 202 is equipped with a second temperature detection device F2. The fourth valve V4, the fifth valve V5 and the sixth valve V6 are all control valves. The fourth valve V4, the fifth valve V5 and the sixth valve V6 are all controlled to open and close according to the exhaust temperature detected by the second temperature detection device F2.

[0084] This is a preferred embodiment of the alternative embodiments of the present invention (in this embodiment, the first air supply device does not supply air to the second compression device), such as Figure 2 Furthermore, the present invention further connects the second air supply device to the intake port of the second compression device via a fourth air supply pipeline. The fourth air supply pipeline is equipped with a fourth valve, which is a control valve. The fourth valve is opened and closed based on the exhaust temperature detected by the second temperature detection device. Additionally, the third air supply device connects to the intake port and air supply port of the second compression device via a fifth air supply pipeline and a sixth air supply pipeline, respectively. The fifth air supply pipeline is equipped with a fifth valve, and the sixth air supply pipeline is equipped with a sixth valve. Both the fifth and sixth valves are control valves, and their opening and closing are controlled based on the exhaust temperature detected by the second temperature detection device. This allows the second and third air replenishment devices to selectively replenish air to the intake and replenishment ports of the second compressor based on the exhaust temperature of the second compressor, forming a reasonable air replenishment control scheme. This further reduces the exhaust temperature of the second compressor to a specified temperature range, improving temperature control accuracy and ensuring that the exhaust temperature does not become too high. This further avoids shutdown due to exhaust protection of the second compressor and prevents wear and tear. At the same time, it can increase the amount of air replenished to the second compressor, thereby improving heating / cooling capacity and increasing the outlet water temperature. This effectively solves the problem that the compressor pressure ratio is too high to meet the high outlet water temperature in ultra-low temperature environments, and effectively improves the outlet water temperature.

[0085] In some implementations...

[0086] It also includes a first heat exchanger 8, a second heat exchanger 6, a first throttling device E1, a second throttling device E2, a third throttling device E3, a third pipeline 203, a fourth pipeline 204, a fifth pipeline 205, and a tenth pipeline 210. The first gas supply device 4 is connected to one end of the first heat exchanger 8 through the third pipeline 203. The first throttling device E1 is installed on the third pipeline 203. The second gas supply device 5 is connected to the first gas supply device 4 through the fourth pipeline 204. The second throttling device E2 is installed on the fourth pipeline 204. The second gas supply device 5 is connected to the third gas supply device 10 through the fifth pipeline 205. The third throttling device E3 is installed on the fifth pipeline 205. The third gas supply device 10 is connected to one end of the second heat exchanger 6 through the tenth pipeline 210. The fourth throttling device E4 is installed on the tenth pipeline 210.

[0087] This is a further preferred structural form of the heat pump unit of the present invention, namely, a throttling device is set on the pipelines connecting the three gas supply devices to the first and second heat exchangers respectively and on the pipeline between the two gas supply devices, which can realize the purpose of throttling flashing and gas supply to different compression units, and meet the requirements of gas supply pressure and flow rate.

[0088] In some implementations...

[0089] It also includes a four-way valve 7, a gas-liquid separator 9, a sixth pipe 206, a seventh pipe 207, an eighth pipe 208, and a ninth pipe 209. The outlet of the second compression device 2 is connected to the first end of the four-way valve 7 through the second pipe 202. The first heat exchanger 8 is connected to the second end of the four-way valve 7 through the sixth pipe 206. The second heat exchanger 6 is connected to the third end of the four-way valve 7 through the seventh pipe 207. The gas-liquid separator 9 is connected to the fourth end of the four-way valve 7 through the eighth pipe 208. The gas-liquid separator 9 is also connected to the intake port of the first compression device 1 through the ninth pipe 209.

[0090] This is a further preferred structural form of the heat pump unit of the present invention. The four-way valve structure enables the switching between cooling mode and heating mode, and the ninth pipeline can provide refrigerant to the suction port of the first compression device.

[0091] The present invention also provides a control method for a heat pump unit as described above, comprising:

[0092] The detection step involves detecting the exhaust temperature T1 of the first compression device using the first temperature detection device F1.

[0093] The judgment step is to determine the relationship between T1 and the first preset temperature a;

[0094] Control step: when T1≥a, open the first valve V1 to supply gas through the gas supply port of the first cylinder 11; when T1<a-x, close the first valve V1 to stop gas supply; when a-x≤T1<a, the first valve V1 maintains its original state; where x is a constant.

[0095] This is the preferred control method of Embodiment 1 of the present invention. That is, when the detected temperature T1 of F1≥a, open the first valve V1 to supply gas through the low-pressure cylinder (at this time, it indicates that the exhaust temperature is slightly high and the amount of refrigerant in the low-pressure stage is relatively small, so it is necessary to appropriately open and weakly supply gas to appropriately reduce the exhaust temperature and prevent the exhaust temperature from being too high); when the detected T1<a-x, close the first valve V1 to stop gas supply (at this time, it indicates that the exhaust temperature is very low and no gas supply is required); when the detected temperature of F1 a>T1≥a-x, the first valve V1 maintains its original state (at this time, it indicates that the exhaust temperature is moderate, and maintaining the current state can ensure that the exhaust temperature is within the required range). It can achieve the control of the first stage, control the opening and closing of the two gas supply pipelines according to the exhaust temperature of the first compression device, so that while ensuring that the exhaust temperature of the first compression device is not too high and meeting the precise temperature control within the specified range, it can also increase or decrease the gas supply amount to make the gas supply amount meet the requirements, and at the same time ensure that the heating / cooling capacity of the heat exchanger in the system reaches the maximum (ensure that the exhaust temperature is within the specified range and at the same time improve the refrigeration / heating capacity), and improve the energy efficiency of the heat pump system.

[0096] In some embodiments,

[0097] In the judgment step, the relationship between T1 and the second preset temperature b is also judged, where b>a;

[0098] In the control step, when T1≥b, open the first valve V1 and the second valve V2 to supply gas simultaneously through the gas supply port of the first cylinder 11 and the gas supply port of the intermediate cavity 12; when T1<b-x, open the first valve V1 and close the second valve V2; when b-x≤T1<b, the first valve V1 and the second valve V2 maintain their original states, and at this time b-x≥a.

[0099] This is a further preferred control method of the present invention. That is, when it is detected that the temperature T1 of F1 ≥ b, the first valve V1 and the second valve V2 are opened, and air is supplemented through the low-pressure cylinder and the intermediate air supplement port (at this time, it indicates that the exhaust temperature is relatively high, and the refrigerant amounts in the low-pressure stage and the intermediate chamber are relatively small. It is necessary to open the air supplement of the first cylinder and the intermediate chamber simultaneously to reduce the exhaust temperature and prevent the exhaust temperature from being too high); when it is detected that T1 < b - x, the first valve V1 is opened and the second valve V2 is closed (at this time, it indicates that the exhaust temperature is slightly high, and the refrigerant amount in the low-pressure stage is relatively small. Only the air supplement of the first cylinder needs to be opened and weakly supplemented to appropriately reduce the exhaust temperature and prevent the exhaust temperature from being too high); when it is detected that the temperature T1 of F1 satisfies b > T1 ≥ b - x, the first valve V1 and the second valve V2 maintain their original states, and at this time b - x ≥ a (at this time, it indicates that the exhaust temperature is moderate, and maintaining the current state can ensure that the exhaust temperature is within the required range interval). It can control the exhaust temperature of the second stage, and control the opening and closing conditions of the two air supplement pipelines according to the exhaust temperature of the first compression device, so as to ensure that the exhaust temperature of the first compression device is not too high, meet the precise temperature control within the specified range interval, and at the same time increase or decrease the air supplement amount to make the air supplement amount meet the requirements, and at the same time ensure that the heating / cooling capacity of the heat exchanger in the system reaches the maximum (ensure that the exhaust temperature is within the specified interval and at the same time improve the refrigeration / heating capacity), and improve the energy efficiency of the heat pump system.

[0100] In some embodiments,

[0101] In the determination step, the relationship between T1 and a third preset temperature c is also determined, where c > b;

[0102] In the control step, when T1 ≥ c, the first valve V1, the second valve V2 and the third valve V3 are opened simultaneously, and air is supplemented simultaneously through the air supplement port of the first cylinder 11, the air supplement port of the intermediate chamber 12 and the air supplement port of the second cylinder 13; when T1 < c - x, the first valve V1 and the second valve V2 are opened, and the third valve V3 is closed; when c - x ≤ T1 < c, the first valve V1, the second valve V2 and the third valve V3 maintain their original states, and at this time c - x ≥ b.

[0103] This is a further preferred control method of the present invention. That is, when it is detected that the temperature T1 of F1 ≥ c, the first valve V1, the second valve V2, and the third valve V3 are opened, and air is supplemented simultaneously through the low-pressure cylinder, the intermediate air supplement port, and the high-pressure cylinder (at this time, it indicates that the exhaust temperature is relatively high, and the refrigerant amounts in the low-pressure stage, the intermediate chamber, and the high-pressure stage are all relatively small. It is necessary to open the air supplement of the first cylinder, the intermediate chamber, and the second cylinder simultaneously to reduce the exhaust temperature and prevent the exhaust temperature from being too high); when it is detected that T1 < c - x, the first valve V1 and the second valve V2 are opened, and the third valve V3 is closed (at this time, it indicates that the exhaust temperature is slightly high, and the refrigerant amount in the low-pressure stage is relatively small. Only the air supplement of the first cylinder and the intermediate chamber needs to be opened and supplemented weakly to appropriately reduce the exhaust temperature and prevent the exhaust temperature from being too high); when it is detected that the temperature T1 of F1 satisfies c > T1 ≥ c - x, the first valve V1, the second valve V2, and the third valve V3 all maintain their original states, and at this time c - x ≥ b (at this time, it indicates that the exhaust temperature is moderate, and maintaining the current state can ensure that the exhaust temperature is within the required range interval). It can achieve the control of the exhaust temperature of the first stage. According to the exhaust temperature of the first compression device, the opening and closing conditions of the three air supplement pipelines are controlled, so that while ensuring that the exhaust temperature of the first compression device is not too high and meeting the precise temperature control within the specified range interval, the air supplement amount can also be increased or decreased to make the air supplement amount meet the requirements, and at the same time ensure that the heating / cooling capacity of the heat exchanger in the system reaches the maximum (ensure that the exhaust temperature is within the specified interval and at the same time improve the refrigeration / heating capacity), and improve the energy efficiency of the heat pump system.

[0104] In some embodiments,

[0105] In the detection step, the exhaust temperature T2 of the second compression device 2 is also detected by the second temperature detection device F2;

[0106] In the judgment step, the relationship between T2 and the fourth preset temperature d is judged;

[0107] In the control step, when T2 ≥ d, the fourth valve V4 is opened, and air is supplemented through the suction port of the second compression device 2; when T2 < d - y, the fourth valve V4 is closed; when d - y ≤ T2 < d, the first valve V1, the second valve V2, the third valve V3, and the fourth valve V4 all maintain their original states; where y is a constant.

[0108] This is the preferred control method of the present invention. That is, when it is detected that the temperature T2 of F2 ≥ d, the fourth valve V4 is opened, and air is supplemented to the suction port of the second compression device through the first air supplement device (or the second air supplement device of the alternative embodiment) (at this time, it indicates that the exhaust temperature of the second compression device is slightly high and its refrigerant volume is relatively small, and it is necessary to appropriately open and weakly supplement air to appropriately reduce the exhaust temperature and prevent the exhaust temperature from being too high); when it is detected that T2 < d - y, the fourth valve V4 is closed (at this time, it indicates that the exhaust temperature of the second compression device is very low and no air supplementation is required); when it is detected that the temperature T2 of F2 satisfies d > T2 ≥ d - y, the first valve V1, the second valve V2, the third valve V3, and the fourth valve V4 maintain their original states (at this time, it indicates that the exhaust temperature of the second compression device is moderate, and maintaining the current state can ensure that the exhaust temperature is within the required range). It can achieve the control of the first stage of the second compression device, and control the opening and closing of the two air supplement pipelines according to the exhaust temperature of the second compression device, so that while ensuring that the exhaust temperature of the second compression device is not too high and meeting the precise temperature control within the specified range, the air supplement volume can also be increased or decreased to make the air supplement volume meet the requirements, and at the same time ensure that the heating / cooling capacity of the heat exchanger in the system reaches the maximum (ensuring that the exhaust temperature is within the specified range and at the same time improving the refrigeration / heating capacity), thereby improving the energy efficiency of the heat pump system.

[0109] In some embodiments,

[0110] In the judgment step, the relationship between T2 and the fifth preset temperature e is judged, where e > d;

[0111] In the control step, when T2 ≥ e, the fifth valve V5 is opened, the fourth valve V4 is closed, and air is supplemented through the suction port of the second compression device 2; when T2 < e - y, the fifth valve V5 is closed and the fourth valve V4 is opened; when e - y ≤ T2 < e, the first valve V1, the second valve V2, the third valve V3, the fourth valve V4, and the fifth valve V5 all maintain their original states, and at this time e - y ≥ d.

[0112] This is a further preferred control method of the present invention. That is, when it is detected that the temperature T2 of F2 ≥ e, the fifth valve V5 is opened, and the fourth valve V4, the sixth valve V6, and the seventh valve are closed (which can effectively avoid the situation where the refrigerant supplemented by the fifth valve leaks from the fourth valve, resulting in a reduction in the air supplement amount of the second compression device. Since the pressure of the second air supplement device is higher than that of the first air supplement device, the air supplement amount supplemented through the fifth valve is greater than that supplemented through the fourth valve), and air is supplemented through the suction port of the second compression device (at this time, it indicates that the exhaust temperature of the second compression device is relatively high and its refrigerant amount is relatively small, and it is necessary to open the fifth valve to supplement air from the suction port of the second compression device, so as to effectively reduce the exhaust temperature of the second compression device and prevent its exhaust temperature from being too high); when it is detected that T2 < e - y, the fourth valve V4 is opened and the fifth valve V5 is closed (at this time, it indicates that the exhaust temperature of the second compression device is slightly high and the refrigerant amount is relatively small, and only the fourth valve needs to be opened to supplement air weakly from the suction port of the second compression device, which can appropriately reduce the exhaust temperature of the second compression device and prevent its exhaust temperature from being too high); when it is detected that the temperature T2 of F2 satisfies e > T2 ≥ e - y, the first valve V1, the second valve V2, the third valve V3, the fourth valve V4, the fifth valve V5, and the sixth valve V6 maintain their original states (at this time, it indicates that the exhaust temperature of the second compression device is moderate, and maintaining the current state can ensure that the exhaust temperature is within the required range interval). It is possible to control the exhaust temperature of the second stage (the exhaust temperature of the second stage is higher than that of the first stage) of the second compression device, and control the opening and closing conditions of the two air supplement pipelines of the second compression device according to the exhaust temperature of the second compression device, so that while ensuring that the exhaust temperature of the second compression device is not too high and meeting the precise temperature control within the specified range interval, the air supplement amount can be increased or decreased to make the air supplement amount meet the requirements, and at the same time ensure that the heating / cooling capacity of the heat exchanger in the system reaches the maximum (ensure that the exhaust temperature is within the specified interval and at the same time improve the refrigeration / heating capacity), and improve the energy efficiency of the heat pump system.

[0113] In some embodiments,

[0114] In the judgment step, the relationship between T2 and the sixth preset temperature f is judged, where f > e;

[0115] In the control step, when T2 ≥ f, the sixth valve V6 is opened, the fourth valve V4 and the fifth valve V5 are closed, and air is supplemented through the suction port (or in an alternative embodiment, through the air supplement port) of the second compression device 2; when it is detected that T2 < f - y, the fifth valve V5 is opened, and the fourth valve V4 and the sixth valve V6 are closed; when f - y ≤ T2 < f, the first valve V1, the second valve V2, the third valve V3, the fourth valve V4, the fifth valve V5, and the sixth valve V6 all maintain their original states, and at this time f - y ≥ e.

[0116] This is a further preferred control method of the present invention. That is, when it is detected that the temperature T2 of F2 ≥ f, the sixth valve V6 is opened, and the fourth valve V4 and the fifth valve V5 are closed (which can effectively avoid the situation that the refrigerant supplemented by the sixth valve leaks from the fourth valve or the fifth valve, resulting in a reduction in the air supplement amount of the second compression device. Since the pressure of the third air supplement device is higher than that of the second and first air supplement devices, the air supplement amount supplemented by it through the sixth valve is greater than that supplemented by the fifth or fourth valve), and the air is supplemented to the suction port of the second compression device through the third air supplement device (at this time, it indicates that the exhaust temperature of the second compression device is very high, and the third air supplement device needs to be opened to supplement the air to the suction port of the second compression device through the sixth valve, so as to effectively reduce the exhaust temperature of the second compression device and prevent its exhaust from being too high); when it is detected that T2 < f - y, the fifth valve V5 is opened, and the fourth valve V4 and the sixth valve V6 are closed (at this time, it indicates that the exhaust temperature of the second compression device is relatively high, and only the second air supplement device needs to be opened to supplement the air to the suction port and the air supplement port of the second compression device, which can appropriately reduce the exhaust temperature of the second compression device and prevent its exhaust from being too high); when it is detected that the temperature f of F2 > T2 ≥ f - y, the first valve V1, the second valve V2, the third valve V3, the fourth valve V4, the fifth valve V5, and the sixth valve V6 (at this time, it indicates that the exhaust temperature of the second compression device is moderate, and maintaining the current state can ensure that the exhaust temperature is within the required range), it is possible to control the exhaust temperature of the third stage (the exhaust temperature of the third stage is higher than that of the second stage) of the second compression device. According to the exhaust temperature of the second compression device, the opening and closing conditions of the air supplement pipelines of the second and third air supplement devices are controlled, so that while ensuring that the exhaust temperature of the second compression device is not too high and meeting the precise temperature control within the specified range, the air supplement amount can also be increased or decreased to make the air supplement amount meet the requirements, and at the same time ensure that the heating / cooling capacity of the heat exchanger in the system reaches the maximum (ensuring that the exhaust temperature is within the specified range and at the same time improving the refrigeration / heating capacity), thereby improving the energy efficiency of the heat pump system.

[0117] In some embodiments,

[0118] In the determination step, the relationship between T2 and the seventh preset temperature g is determined, where g > f;

[0119] In the control step, when T2 ≥ g, the fifth valve V5 and the seventh valve V7 are opened, the fourth valve V4 and the sixth valve V6 are closed, and the air is supplemented through the suction port and the air supplement port of the second compression device 2; when it is detected that T2 < g - y, the sixth valve V6 is opened, and the fifth valve V5, the seventh valve V7, and the fourth valve V4 are closed; when g - y ≤ T2 < g, the first valve V1, the second valve V2, the third valve V3, the fourth valve V4, the fifth valve V5, the sixth valve V6, and the seventh valve V7 all maintain their original states, and at this time g - y ≥ f.

[0120] This is a further preferred control method of the present invention. That is, when it is detected that the temperature T2 of F2 ≥ g, the fifth valve V5 and the seventh valve V7 are opened, and the fourth valve V4 and the sixth valve V6 are closed (the fifth valve and the seventh valve respectively supply air to the suction port and the gas replenishment port of the second compression device, and there will be no gas leakage phenomenon, which can increase the gas replenishment volume. At the same time, it can effectively prevent the refrigerant replenished by the fifth and seventh valves from leaking from the fourth valve or the sixth valve, resulting in a reduction in the gas replenishment volume of the second compression device. Since the pressure of the third gas replenishment device is higher than that of the second and first gas replenishment devices, the gas replenishment volume replenished through the seventh valve is greater than that replenished through the fifth or fourth valve), and the third gas replenishment device supplies air to the suction port of the second compression device (at this time, it indicates that the exhaust temperature of the second compression device is very high. The second and third gas replenishment devices are opened simultaneously, and the fifth valve and the seventh valve supply air to the suction port and the gas replenishment port of the second compression device respectively, so as to effectively reduce the exhaust temperature of the second compression device and prevent its exhaust from being too high); when it is detected that T2 < g - y, the sixth valve V6 is opened, and the fourth valve V4, the fifth valve V5 and the seventh valve V7 are closed (at this time, it indicates that the exhaust temperature of the second compression device is relatively high. Only the third gas replenishment device needs to be opened to supply air to the suction port of the second compression device, which can appropriately reduce the exhaust temperature of the second compression device and prevent its exhaust from being too high); when it is detected that the temperature of F2, g > T2 ≥ g - y, the first valve V1, the second valve V2, the third valve V3, the fourth valve V4, the fifth valve V5, the sixth valve V6 and the seventh valve V7 (at this time, it indicates that the exhaust temperature of the second compression device is moderate. Maintaining the current state can ensure that the exhaust temperature is within the required range), it is possible to control the exhaust temperature of the fourth stage (the exhaust temperature of the fourth stage is higher than that of the third stage) of the second compression device. According to the exhaust temperature of the second compression device, the opening and closing conditions of the gas replenishment pipelines of the second and third gas replenishment devices are controlled, so that while ensuring that the exhaust temperature of the second compression device is not too high and meeting the precise temperature control within the specified range, the gas replenishment volume can be increased or decreased to make the gas replenishment volume meet the requirements, and at the same time ensure that the heating / cooling capacity of the heat exchanger in the system reaches the maximum (ensure that the exhaust temperature is within the specified range and at the same time improve the cooling / heating capacity), and improve the energy efficiency of the heat pump system.

[0121] In some embodiments,

[0122] In the judgment step, the relationship between T2 and the eighth preset temperature h is judged, where h > g;

[0123] In the control step, when T2≥h, open the sixth valve V6 and the seventh valve V7, close the fourth valve V4 and the fifth valve V5, and supplement air through the suction port and the air supplement port of the second compression device 2; when it is detected that T2<h-y, open the fifth valve V5, and close the sixth valve V6, the seventh valve V7 and the fourth valve V4; when h-y≤T2<h, the first valve V1, the second valve V2, the third valve V3, the fourth valve V4, the fifth valve V5, the sixth valve V6 and the seventh valve V7 all maintain their original states, and at this time g-y≥f.

[0124] This is a further preferred control method of the present invention. That is, when the temperature T2 of F2 is detected to be T2≥h, open the sixth valve V6 and the seventh valve V7 connected to the third air supplement device, and close the fourth valve V4 and the fifth valve V5 (the sixth valve and the seventh valve respectively supplement air to the suction port and the air supplement port of the second compression device, and there will be no air leakage phenomenon, which can increase the air supplement volume. At the same time, it can effectively avoid the situation that the refrigerant supplemented by the sixth and seventh valves leaks from the fourth or fifth valve, resulting in a reduction in the air supplement volume of the second compression device. Since the pressure of the third air supplement device is higher than that of the second and first air supplement devices, the air supplement volume supplemented by it through the sixth and seventh valves is greater than that supplemented by the fifth or fourth valve), and supplement air to the suction port of the second compression device through the third air supplement device (at this time, it indicates that the exhaust temperature of the second compression device is very high. Open the third air supplement device and supplement air to the suction port and the air supplement port of the second compression device through the sixth valve and the seventh valve respectively, so as to effectively reduce the exhaust temperature of the second compression device and prevent its exhaust temperature from being too high); when it is detected that T2<h-y, open the fifth valve V5, and close the fourth valve V4, the sixth valve V6 and the seventh valve V7 (at this time, it indicates that the exhaust temperature of the second compression device is relatively high. Only need to open the third air supplement device to supplement air to the suction port of the second compression device, which can appropriately reduce the exhaust temperature of the second compression device and prevent its exhaust temperature from being too high); when it is detected that the temperature of F2 is h>T2≥h-y, the first valve V1, the second valve V2, the third valve V3, the fourth valve V4, the fifth valve V5, the sixth valve V6 and the seventh valve V7 remain in an unchanged state (at this time, it indicates that the exhaust temperature of the second compression device is moderate. Maintaining the current state can ensure that the exhaust temperature is within the required range), which can realize the control of the exhaust temperature of the fifth stage (the exhaust temperature of the fifth stage is higher than that of the fourth stage) of the second compression device. According to the exhaust temperature of the second compression device, the opening and closing conditions of the air supplement pipeline of the third air supplement device are controlled, so that while ensuring that the exhaust temperature of the second compression device is not too high and meeting the precise temperature control within the specified range, the air supplement volume can also be increased or decreased to make the air supplement volume meet the requirements, and at the same time ensure that the heating / cooling capacity of the heat exchanger in the system reaches the maximum (ensure that the exhaust temperature is within the specified range and at the same time improve the refrigeration / heating capacity), and improve the energy efficiency of the heat pump system.

[0125] Therefore, the present invention can divide the temperature into multiple temperature ranges based on the exhaust temperature of the first and second compression devices, and realize different gas replenishment methods for each different range of exhaust temperature. Ultimately, the exhaust temperature can be controlled within the specified temperature range, achieving precise control of the exhaust temperature. At the same time, the gas replenishment amount can meet the heating / cooling requirements, maximizing the heating / cooling capacity. Through a reasonable gas replenishment control scheme, the present invention improves the heating / cooling capacity by 5% and the energy efficiency by 3%.

[0126] This invention leads out different air supply circuits through a first air supply device (preferably a flash evaporator), a second air supply device (preferably a flash evaporator), and a third air supply device (preferably a flash evaporator). By detecting the exhaust temperature, different air supply schemes are achieved by controlling the solenoid valve switch on the circuit, which effectively reduces and can accurately control the exhaust temperature, improves system reliability, and enhances the overall performance of the machine.

[0127] Remark:

[0128] 1. The multiple parameters of the present invention satisfy h>g>f>e>d>c>b>a, where h~a can be between 105 and 70 degrees, or other reasonable values.

[0129] 2. x and y are positive numbers, both in ℃, and satisfy 10>x≥3 and 20>y≥3. There is no size relationship between x and y.

[0130] like Figure 1 The optimal implementation of this invention is as follows:

[0131] Taking the heating cycle as an example, the main circulation path is as follows:

[0132] The first cylinder 11 (low-pressure cylinder) of the first compression unit 1 (low-pressure stage compressor) receives low-temperature, low-pressure refrigerant vapor from the gas-liquid separator 9. After compression in the low-pressure cylinder, the vapor enters the second cylinder 13 (high-pressure cylinder). After secondary compression in the high-pressure cylinder, the vapor passes through the one-way valve 3 and connecting pipes to the suction port of the second compression unit 2 (high-pressure stage compressor). In the second compression unit 2, the vapor is compressed into high-temperature, high-pressure superheated vapor. The vapor then flows from the exhaust port to the four-way valve 7, and then to the second heat exchanger 6 (preferably a water-fluorine heat exchanger). In the water-fluorine heat exchanger, the vapor exchanges heat with low-temperature water and is cooled into high-pressure, medium-temperature liquid refrigerant. The liquid refrigerant then exits the second heat exchanger 6 and flows through the connecting pipe to the fourth throttling device E4 (preferably an electronic expansion valve). After pressure reduction, the liquid refrigerant enters the third gas injection device 10 (preferably a liquid receiver or flash evaporator). In the third gas injection device 10, the liquid refrigerant is subcooled by the flashed vaporized refrigerant and then flows through the connecting pipe to the third throttling device E4. 3 (preferably an electronic expansion valve), after throttling and depressurization, enters the second gas supply device 5 (preferably a liquid receiver or flash evaporator). In the second gas supply device 5, the liquid refrigerant is subcooled by the flashed vapor refrigerant and reaches the second throttling device E2 (preferably an electronic expansion valve) through the connecting pipe. After throttling and depressurization again, it enters the first gas supply device 4 (preferably a liquid receiver or flash evaporator). In the first gas supply device 4, the main liquid refrigerant is subcooled and reaches the first throttling device E1 (preferably an electronic expansion valve) through the connecting pipe. After throttling and depressurization, it becomes a low-pressure vapor-liquid mixture and enters the first heat exchanger 8 (preferably a finned heat exchanger). After absorbing heat in the first heat exchanger 8, it evaporates into a low-pressure vapor refrigerant and enters the four-way valve 7. It then enters the gas-liquid separator 9 through the connecting pipe and then enters the first cylinder 11 (low-pressure cylinder) of the first compression device 1 (low-pressure stage compressor) from the suction port, completing one cycle.

[0133] The corresponding airflow path is as follows:

[0134] The refrigerant vapor from the first gas supply device 4 passes through the first valve V1 to the low-pressure cylinder gas supply port of the first cylinder 11 when the first valve V1 is open; if the second valve V2 is open, it enters the intermediate gas supply port of the first compression device 1; if the third valve V3 is open, it enters the high-pressure cylinder gas supply port of the first compression device 1. When the fourth valve V4 is open, it mixes with the exhaust gas from the first compression device 1 and enters the suction port of the second compression device 2.

[0135] The refrigerant vapor from the second gas replenishment device 5 enters the suction port of the second compression device 2 through the connecting pipeline when the fifth valve V5 is opened.

[0136] The refrigerant vapor coming out of the third air supplement device 10, through the connecting pipeline, when the sixth valve V6 is opened, passes through the sixth valve V6 and enters the suction port of the second compression device 2; when the seventh valve V7 is opened, it passes through the seventh valve V7 and enters the air supplement port of the second compression device 2. Through the on-off control of the solenoid valve, according to different air supplement requirements, the refrigerant circulation amount is increased, the exhaust temperature is reduced, the capacity and energy efficiency are improved, and the reliability of the whole machine is enhanced.

[0137] Logical relationship between solenoid valve on-off control and exhaust temperature:

[0138] 1. When it is detected that the temperature T1 of F1 ≥ a, the first valve V1 is opened to supplement air through the low-pressure cylinder; when it is detected that T1 < a - x, the first valve V1 is closed without air supplement; when it is detected that the temperature a > T1 ≥ a - x of F1, the first valve V1 maintains its original state.

[0139] 2. When it is detected that the temperature T1 of F1 ≥ b, the first valve V1 and the second valve V2 are opened to supplement air through the low-pressure cylinder and the intermediate air supplement port; when it is detected that T1 < b - x, the first valve V1 is opened and the second valve V2 is closed; when it is detected that the temperature b > T1 ≥ b - x of F1, the first valve V1 and the second valve V2 maintain their original states, and at this time b - x ≥ a.

[0140] 3. When it is detected that the temperature T1 of F1 ≥ c, the first valve V1, the second valve V2 and the third valve V3 are opened to supplement air through the low-pressure cylinder, the intermediate air supplement port and the high-pressure cylinder; when it is detected that T1 < c - x, the third valve V3 is closed, the first valve V1 is opened and the second valve V2 is opened; when it is detected that the temperature c > T1 ≥ c - x of F1, the first valve V1, the second valve V2 and the third valve V3 all maintain their original states.

[0141] 4. When it is detected that the temperature T2 of F2 ≥ d, the fourth valve V4 is opened, the fifth valve V5 and the sixth valve V6 are closed, and air is supplemented to the suction port of the second compression device through the first air supplement device; when it is detected that T2 < d - y, the fourth valve V4, the fifth valve V5 and the sixth valve V6 are closed; when it is detected that the temperature d > T2 ≥ d - y of F2, the fourth valve V4, the fifth valve V5 and the sixth valve V6 maintain their original states, and at this time d - y ≥ c.

[0142] 5. When it is detected that the temperature T2 of F2 ≥ e, the fifth valve V5 is opened, the fourth valve V4 and the sixth valve V6 are closed, and air is supplemented to the suction of the second compression device through the second air supplement device; when it is detected that T2 < e - y, the fourth valve V4 is opened, the fifth valve V5 and the sixth valve V6 are closed; when it is detected that the temperature e > T2 ≥ e - y of F2, the fourth valve V4, the fifth valve V5 and the sixth valve V6 maintain their original states, and at this time e - y ≥ d.

[0143] 6. When it is detected that the temperature T2 of F2 ≥ f, open the sixth valve V6, close the fourth valve V4 and the fifth valve V5, and supplement gas to the suction port of the second compression device through the third gas supplement device; when it is detected that T2 < f - y, open the fifth valve V5, close the fourth valve V4 and the sixth valve V6; when it is detected that the temperature of F2 f > T2 ≥ f - y, the fourth valve V4, the fifth valve V5 and the sixth valve V6 all maintain their original states, and at this time f - y ≥ e.

[0144] 7. When it is detected that the temperature T2 of F2 ≥ g, open the fifth valve V5 and the seventh valve V7, close the sixth valve V6 and the fourth valve V4, and supplement gas to the suction port and the gas supplement port of the second compression device 2 with refrigerant vapor from the second and third gas supplement devices through the connecting pipeline; at this time, the system supplements gas through the low-pressure cylinder gas supplement port, the intermediate gas supplement port, the high-pressure cylinder gas supplement port of the first compression device 1, the suction port and the gas supplement port of the second compression device 2; when it is detected that T2 < g - y, close the seventh valve V7 and the fifth valve V5, and open the sixth valve V6; when it is detected that the temperature of F2 g > T2 ≥ g - y, the first valve V1, the second valve V2, the third valve V3, the fourth valve V4, the fifth valve V5, the sixth valve V6 and the seventh valve V7 all maintain their original states, and at this time g - y ≥ f.

[0145] 8. When it is detected that the temperature T2 of F2 ≥ h, open the sixth valve V6 and the seventh valve V7, close the fifth valve V5 and the fourth valve V4, and supplement gas to the suction port and the gas supplement port of the second compression device 2 with refrigerant vapor from the third gas supplement device through the connecting pipeline; at this time, the system supplements gas through the low-pressure cylinder gas supplement port, the intermediate gas supplement port, the high-pressure cylinder gas supplement port of the first compression device 1, the suction port and the gas supplement port of the second compression device 2; when it is detected that T2 < h - y, close the sixth valve V6, and open the fifth valve V5; when it is detected that the temperature of F2 h > T2 ≥ h - y, the first valve V1, the second valve V2, the third valve V3, the fourth valve V4, the fifth valve V5, the sixth valve V6 and the seventh valve V7 all maintain their original states, and at this time h - y ≥ g.

[0146] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention. The above is only the preferred implementation manner of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and variations can still be made, and these improvements and variations should also be regarded as within the protection scope of the present invention.

Claims

1. A heat pump unit, characterized in that: include: The first compression device (1) and the second compression device (2), the first air supply device (4), the second air supply device (5) and the third air supply device (10), the first compression device (1) includes a first cylinder (11), an intermediate chamber (12) and a second cylinder (13), the exhaust of the first cylinder (11) enters the intermediate chamber (12), the exhaust of the intermediate chamber (12) enters the second cylinder (13) to form at least two-stage compression, and the exhaust of the first compression device (1) enters the intake port of the second compression device (2); The first air supply device (4) can supply air to at least one of the first cylinder (11), the intermediate chamber (12) and the second cylinder (13). The second air supply device (5) and the third air supply device (10) can both supply air to the second compression device (2). The first air supply device (4) can control the air supply to the first cylinder (11), the intermediate chamber (12) and the second cylinder (13) according to the exhaust temperature of the first compression device (1). The second air supply device (5) and the third air supply device (10) can both control the air supply to the second compression device (2) according to the exhaust temperature of the second compression device (2).

2. The heat pump unit according to claim 1, characterized in that: The first air supply device (4) is connected to the air supply port of the first cylinder (11) through the first air supply pipeline (101), and a first valve (V1) is provided on the first air supply pipeline (101). The first air supply device (4) is connected to the air supply port of the intermediate cavity (12) through the second air supply pipeline (102), and a second valve (V2) is provided on the second air supply pipeline (102). The first air supply device (4) is connected to the air supply port of the second cylinder (13) through the third air supply pipeline (103), and a third valve (V3) is provided on the third air supply pipeline (103). The outlet of the second cylinder (13) is connected to the intake port of the second compression device (2) through the first pipeline (201). The first pipeline (201) is equipped with a first temperature detection device (F1). The first valve (V1), the second valve (V2) and the third valve (V3) are all control valves. The first valve (V1), the second valve (V2) and the third valve (V3) are all controlled to open and close according to the exhaust temperature detected by the first temperature detection device (F1).

3. The heat pump unit according to claim 2, characterized in that: The first air supply device (4) can also supply air to the intake port of the second compression device (2). The first air supply device (4) can control the supply of air to the second compression device (2) according to the exhaust temperature of the second compression device (2). The first air replenishment device (4) is connected to the air intake of the second compression device (2) through the fourth air replenishment pipeline (104), and a fourth valve (V4) is provided on the fourth air replenishment pipeline (104); the second air replenishment device (5) is connected to the air intake of the second compression device (2) through the fifth air replenishment pipeline (105), and a fifth valve (V5) is provided on the fifth air replenishment pipeline (105). The outlet of the second compression device (2) is vented through the second pipeline (202). The second pipeline (202) is equipped with a second temperature detection device (F2). The fourth valve (V4) and the fifth valve (V5) are both control valves. The fourth valve (V4) and the fifth valve (V5) are both controlled to open and close according to the exhaust temperature detected by the second temperature detection device (F2).

4. The heat pump unit according to claim 3, characterized in that: The third air supply device (10) is connected to the intake port of the second compression device (2) through the sixth air supply pipeline (106). The sixth air supply pipeline (106) is equipped with a sixth valve (V6), which is a control valve. The sixth valve (V6) is controlled to open and close according to the exhaust temperature detected by the second temperature detection device (F2). The third air supply device (10) is also connected to the air supply port of the second compression device (2) through the seventh air supply pipeline (107). The seventh air supply pipeline (107) is equipped with a seventh valve (V7), which is a control valve. The seventh valve (V7) is controlled to open and close according to the exhaust temperature detected by the second temperature detection device (F2).

5. The heat pump unit according to claim 2, characterized in that: The second air replenishment device (5) is connected to the air intake of the second compression device (2) through the fourth air replenishment pipeline (104), and a fourth valve (V4) is provided on the fourth air replenishment pipeline (104); the third air replenishment device (10) is connected to the air intake of the second compression device (2) through the fifth air replenishment pipeline (105), and a fifth valve (V5) is provided on the fifth air replenishment pipeline (105); the third air replenishment device (10) is also connected to the air replenishment port of the second compression device (2) through the sixth air replenishment pipeline (106), and a sixth valve (V6) is provided on the sixth air replenishment pipeline (106); The outlet of the second compression device (2) exhausts gas through the second pipeline (202). The second pipeline (202) is equipped with a second temperature detection device (F2). The fourth valve (V4), the fifth valve (V5) and the sixth valve (V6) are all control valves. The fourth valve (V4), the fifth valve (V5) and the sixth valve (V6) are all controlled to open and close according to the exhaust temperature detected by the second temperature detection device (F2).

6. The heat pump unit according to claim 1, characterized in that: It further includes a first heat exchanger (8), a second heat exchanger (6), a first throttling device (E1), a second throttling device (E2), a third throttling device (E3), a fourth throttling device (E4), a third pipeline (203), a fourth pipeline (204), a fifth pipeline (205) and a tenth pipeline (210). The first air supplement device (4) is connected to one end of the first heat exchanger (8) through the third pipeline (203), and the first throttling device (E1) is arranged on the third pipeline (203). The second air supplement device (5) is connected to the first air supplement device (4) through the fourth pipeline (204), and the second throttling device (E2) is arranged on the fourth pipeline (204). The second air supplement device (5) is connected to the third air supplement device (10) through the fifth pipeline (205), and the third throttling device (E3) is arranged on the fifth pipeline (205). The third air supplement device (10) is connected to one end of the second heat exchanger (6) through the tenth pipeline (210), and the fourth throttling device (E4) is arranged on the tenth pipeline (210).

7. The heat pump unit according to claim 6, wherein: It further includes a four-way valve (7), a gas-liquid separator (9), a sixth pipeline (206), a seventh pipeline (207), an eighth pipeline (208) and a ninth pipeline (209). The outlet of the second compression device (2) is connected to the first end of the four-way valve (7) through the second pipeline (202). The first heat exchanger (8) is connected to the second end of the four-way valve (7) through the sixth pipeline (206). The second heat exchanger (6) is connected to the third end of the four-way valve (7) through the seventh pipeline (207). The gas-liquid separator (9) is connected to the fourth end of the four-way valve (7) through the eighth pipeline (208). The gas-liquid separator (9) is further connected to the suction port of the first compression device (1) through the ninth pipeline (209).

8. A control method for a heat pump unit as described in claim 4, characterized in that: It includes: A detection step of detecting the exhaust temperature T1 of the first compression device (1) through the first temperature detection device (F1); A judgment step of judging the relationship between T1 and a first preset temperature a; A control step of opening the first valve (V1) to supplement air through the air supplement port of the first cylinder (11) when T1 ≥ a; closing the first valve (V1) without supplementing air when T1 < a - x; and maintaining the original state of the first valve (V1) when a - x ≤ T1 < a, where x is a constant.

9. The control method according to claim 8, wherein: The judgment step further judges the relationship between T1 and a second preset temperature b, and b > a; In the control step, when T1 ≥ b, open the first valve (V1) and the second valve (V2), and simultaneously supply air through the air inlet of the first cylinder (11) and the air inlet of the intermediate chamber (12); when T1 < b - x, open the first valve (V1) and close the second valve (V2); when b - x ≤ T1 < b, the first valve (V1) and the second valve (V2) maintain their original states, and at this time b - x ≥ a.

10. The control method according to claim 9, wherein: In the judgment step, the relationship between T1 and a third preset temperature c is further judged, where c > b; In the control step, when T1 ≥ c, open the first valve (V1), the second valve (V2) and the third valve (V3) simultaneously, and supply air through the air inlet of the first cylinder (11), the air inlet of the intermediate chamber (12) and the air inlet of the second cylinder (13) simultaneously; when T1 < c - x, open the first valve (V1) and the second valve (V2), and close the third valve (V3); when c - x ≤ T1 < c, the first valve (V1), the second valve (V2) and the third valve (V3) maintain their original states, and at this time c - x ≥ b.

11. The control method according to claim 8, wherein: In the detection step, the exhaust temperature T2 of the second compression device (2) is further detected by the second temperature detection device (F2); In the judgment step, the relationship between T2 and a fourth preset temperature d is judged; In the control step, when T2 ≥ d, open the fourth valve (V4) and supply air through the air inlet of the second compression device (2); when T2 < d - y, close the fourth valve (V4); when d - y ≤ T2 < d, the first valve (V1), the second valve (V2), the third valve (V3) and the fourth valve (V4) all maintain their original states; where y is a constant.

12. The control method according to claim 11, wherein: In the judgment step, the relationship between T2 and a fifth preset temperature e is judged, where e > d; In the control step, when T2 ≥ e, open the fifth valve (V5), close the fourth valve (V4), and supply air through the air inlet of the second compression device (2); when T2 < e - y, close the fifth valve (V5) and open the fourth valve (V4); when e - y ≤ T2 < e, the first valve (V1), the second valve (V2), the third valve (V3), the fourth valve (V4) and the fifth valve (V5) all maintain their original states, and at this time e - y ≥ d.

13. The control method according to claim 12, wherein: In the judgment step, the relationship between T2 and a sixth preset temperature f is judged, where f > e; In the control step, when T2 ≥ f, open the sixth valve (V6), close the fourth valve (V4) and the fifth valve (V5), and supplement air through the suction port of the second compression device (2); when it is detected that T2 < f - y, open the fifth valve (V5), close the sixth valve (V6) and the fourth valve (V4); when f - y ≤ T2 < f, the first valve (V1), the second valve (V2), the third valve (V3), the fourth valve (V4), the fifth valve (V5) and the sixth valve (V6) all maintain their original states, and at this time f - y ≥ e.

14. The control method according to claim 13, wherein: In the determination step, determine the relationship between T2 and the seventh preset temperature g, where g > f; In the control step, when T2 ≥ g, open the fifth valve (V5) and the seventh valve (V7), close the fourth valve (V4) and the sixth valve (V6), and supplement air through the suction port and the air supplement port of the second compression device (2); when it is detected that T2 < g - y, open the sixth valve (V6), close the fifth valve (V5), the seventh valve (V7) and the fourth valve (V4); when g - y ≤ T2 < g, the first valve (V1), the second valve (V2), the third valve (V3), the fourth valve (V4), the fifth valve (V5), the sixth valve (V6) and the seventh valve (V7) all maintain their original states, and at this time g - y ≥ f.

15. The control method according to claim 14, wherein: In the determination step, determine the relationship between T2 and the eighth preset temperature h, where h > g; In the control step, when T2 ≥ h, open the sixth valve (V6) and the seventh valve (V7), close the fourth valve (V4) and the fifth valve (V5), and supplement air through the suction port and the air supplement port of the second compression device (2); when it is detected that T2 < h - y, open the fifth valve (V5), close the sixth valve (V6), the seventh valve (V7) and the fourth valve (V4); when h - y ≤ T2 < h, the first valve (V1), the second valve (V2), the third valve (V3), the fourth valve (V4), the fifth valve (V5), the sixth valve (V6) and the seventh valve (V7) all maintain their original states, and at this time g - y ≥ f.

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