Evaporative cooling system comprising overhead pressure control mechanism and control method

Abstract

The invention relates to the field of generator cooling, in particular to an evaporative cooling system comprising an overhead pressure control mechanism and a control method, and aims to solve the problem that the evaporative cooling system is prone to self-sustaining oscillation under the condition that the load of a generator is suddenly increased or a cooling mechanism fails. In order to achieve the purpose, according to the evaporative cooling system comprising the overhead pressure control mechanism, the space of a pressure control body is divided into the pressure stabilizing space and the pressure control space which are adjustable in space size, and the pressure control space is connected with the exhaust side of the cooling mechanism; when the generator encounters sudden load change or the cooling mechanism breaks down to cause gas gathering, the gas can enter the pressure control space through the first switch element, the size of the pressure control space can be adaptively adjusted according to the air pressure of the exhaust side of the cooling mechanism, and therefore the air pressure of the exhaust side of the cooling mechanism is reduced, and the service life of the cooling mechanism is prolonged. The cooling effect of the stator bar is improved, the flow phase difference between an inlet and an outlet of the stator bar is reduced, and therefore self-sustaining oscillation of the evaporative cooling system is avoided.

Description

Technical Field

[0001] The invention relates to the field of generator cooling, and specifically provides an evaporative cooling system including an overhead pressure control mechanism and a control method. Background Art

[0002] The evaporative cooling system has been widely used in the field of generator cooling due to its high cooling efficiency, excellent high insulation performance, low boiling point characteristics and significant economic efficiency. The system efficiently removes heat from the stator wire rods of the generator through the boiling process of the working fluid, thereby achieving efficient cooling of the generator. However, due to the limited internal space and pressure regulation function of the evaporative cooling system, when faced with a sudden increase in load or failure of the cooling mechanism in the evaporative cooling system, the operating pressure of the system will rise sharply, resulting in an increase in the phase change temperature of the working fluid. This change in turn causes the temperature of the stator wire rod to rise, resulting in a reduction in the length of the working fluid boiling area inside the wire rod, a weakening of the circulation power, and a decrease in the flow rate at the inlet of the stator wire rod. In addition, due to the inertia of the working fluid, there is a time difference between the change of the stator wire rod outlet flow rate and the inlet flow rate. When the outlet flow rate decreases, the system pressure and resistance decrease, and the working fluid phase change temperature decreases, which leads to a decrease in the temperature of the stator wire rod and an increase in the inlet flow rate. This process repeats itself, causing a phase difference in the flow between the inlet and outlet of the stator bar, resulting in a phase difference between the system operating pressure and the circulating flow. This phase difference will usually be slowly eliminated as the system state changes, but when the phase difference stabilizes at a certain state, the system may form self-sustaining oscillations, which will have an adverse effect on the safe operation of the generator.

[0003] Therefore, this field needs a new technical solution to solve the above problems. Summary of the invention

[0004] In order to solve at least one problem in the prior art, that is, to solve the problem that the evaporative cooling system is prone to self-sustaining oscillation when the load suddenly increases or the cooling mechanism fails, the present application provides an evaporative cooling system including an overhead pressure control mechanism, the evaporative cooling system comprising:

[0005] Cooling mechanism;

[0006] An overhead pressure control mechanism, the overhead pressure control mechanism comprising a pressure control body and a partition plate disposed in the pressure control body and dividing the space of the pressure control body into two independent pressure control spaces and a pressure stabilizing space, the partition plate being configured to be able to move up and down according to the air pressure of the pressure control space and the pressure stabilizing space;

[0007] The exhaust mechanism includes a first switch element, which is arranged on the air inlet side of the pressure control space and connected to the exhaust side of the cooling mechanism.

[0008] In a preferred technical solution of the above evaporative cooling system, the exhaust mechanism further includes a second switch element, and the second switch element is arranged on the exhaust side of the pressure controlled space.

[0009] In a preferred technical solution of the above evaporative cooling system, the exhaust mechanism further includes a vacuum pump, and the vacuum pump is connected to the second switch element.

[0010] In a preferred technical solution of the above evaporative cooling system, the exhaust mechanism further includes a third switch element, and the third switch element is arranged on the discharge side of the pressure control space.

[0011] In a preferred technical solution of the above evaporative cooling system, the third switch element is connected to the liquid inlet side of the cooling mechanism.

[0012] In the preferred technical solution of the above evaporative cooling system, the top pressure control mechanism further includes a limiting structure, which is arranged in the pressure control space and is configured to limit the movement of the partition plate.

[0013] In the preferred technical solution of the above-mentioned evaporative cooling system, the cooling mechanism also includes a liquid return pipe, a liquid collecting ring pipe, a gas collecting ring pipe, an air outlet pipe, a condenser, a connecting pipe, a pressure equalizing pipe and a fourth switch element, and the liquid return pipe, the liquid collecting ring pipe, the gas collecting ring pipe, the air outlet pipe, the condenser, the connecting pipe, the pressure equalizing pipe and the fourth switch element are connected in sequence; the pressure equalizing pipe is connected to the first switch element.

[0014] The present application also provides a control method for an evaporative cooling system including an overhead pressure control mechanism, the evaporative cooling system including a cooling mechanism, an overhead pressure control mechanism and an exhaust mechanism, the overhead pressure control mechanism including a pressure control body and a partition plate arranged in the pressure control body and dividing the space of the pressure control body into two independent pressure control spaces and a pressure stabilizing space, the partition plate being arranged to be able to move up and down according to the air pressure of the pressure control space and the pressure stabilizing space; an exhaust mechanism, the exhaust mechanism including a first switch element, the first switch element being arranged at the air inlet side of the pressure control space and connected to the exhaust side of the cooling mechanism; the control method comprising:

[0015] Acquiring the operating state of the generator, wherein the operating state includes a working state and a stop intermittent state;

[0016] When the generator is in an operating state, the first switch element is controlled to remain in an open state.

[0017] In the preferred technical solution of the above control method, when the overhead pressure control mechanism further includes a second switch element arranged on the exhaust side of the pressure control space, the step of "controlling the first switch element to remain in an open state" also includes:

[0018] The second switch element is controlled to remain in a closed state.

[0019] In the preferred technical solution of the above control method, when the top pressure control mechanism further includes a third switch element arranged on the liquid discharge side of the pressure control space, the step of "controlling the first switch element to remain in an open state" also includes:

[0020] The third switch element is controlled to remain in an open state.

[0021] In the preferred technical solution of the above control method, the control method further includes:

[0022] When the generator is in an intermittent stop state, obtaining a first current air pressure on the exhaust side of the cooling mechanism;

[0023] Comparing the first current air pressure with the first preset air pressure;

[0024] When the first current air pressure is greater than or equal to a first preset air pressure, the exhaust mechanism is controlled to perform an exhaust operation.

[0025] In the preferred technical solution of the above control method, when the overhead pressure control mechanism further includes a second switch element arranged on the exhaust side of the pressure control space and a vacuum pump connected to the second switch element, the specific steps of "controlling the exhaust mechanism to perform the exhaust operation" include:

[0026] When the first current air pressure is greater than or equal to the first preset air pressure, the first switch element is closed, the second switch element is opened, and the vacuum pump is controlled to start running;

[0027] Acquire a second current air pressure of the pressure-controlled space;

[0028] comparing the second current air pressure with the second preset air pressure;

[0029] When the second current air pressure is lower than the second preset air pressure, the second switch element is first closed and the vacuum pump is controlled to stop working, and then the first switch element is opened.

[0030] In a preferred technical solution of the above control method, after the step of “opening the first switch element”, the step further includes:

[0031] Then, obtaining a second current air pressure of the pressure-controlled space;

[0032] comparing the second current air pressure with a third preset air pressure;

[0033] When the second current air pressure is greater than or equal to the third preset air pressure, controlling the exhaust mechanism to perform the exhaust operation again;

[0034] Wherein, the third preset air pressure is greater than the second preset air pressure.

[0035] In the preferred technical solution of the above control method, after the step of "controlling the exhaust mechanism to perform the exhaust operation", the following steps are further included:

[0036] After the exhaust mechanism is controlled to perform the exhaust operation, the accumulated exhaust times of the exhaust operation are obtained;

[0037] Comparing the accumulated exhaust times with a preset exhaust times;

[0038] When the accumulated exhaust times is greater than or equal to a preset exhaust times, the exhaust mechanism is controlled to stop the exhaust operation.

[0039] In the preferred technical solution of the above control method, after the step of "controlling the exhaust mechanism to perform the exhaust operation", the following steps are further included:

[0040] After controlling the exhaust mechanism to perform an exhaust operation, obtaining a first current air pressure on an exhaust side of the cooling mechanism;

[0041] comparing the first current air pressure with the first preset air pressure;

[0042] When the first current air pressure is less than the first preset air pressure, the exhaust mechanism is controlled to stop the exhaust operation.

[0043] In the preferred technical solution of the above control method, after the step of "controlling the exhaust mechanism to perform the exhaust operation", the following steps are further included:

[0044] After the exhaust mechanism is controlled to perform the exhaust operation, the generator is in a working state;

[0045] When the generator is in operation, the exhaust mechanism is controlled to stop exhaust operation.

[0046] In the preferred technical solution of the above control method, the step of "controlling the exhaust mechanism to stop exhaust operation" specifically includes:

[0047] The first switch element is opened, the second switch element is closed, and the vacuum pump is controlled to stop working.

[0048] In the preferred technical solution of the above control method, when the overhead pressure control mechanism further includes a third switch element arranged on the discharge side of the pressure control body, after the step of "opening the first switch element, closing the second switch element and controlling the vacuum pump to stop working", it also includes:

[0049] The third switching element is turned on.

[0050] In the preferred technical solution of the above control method, when the overhead pressure control mechanism further includes a third switch element arranged on the discharge side of the pressure control body, before the step of "closing the first switch element, opening the second switch element and controlling the vacuum pump to start operation", the step further includes:

[0051] Turning off the third switching element; and

[0052] The step of “opening the first switch element” further includes:

[0053] The third switching element is turned on.

[0054] Solution 1. An evaporative cooling system including an overhead pressure control mechanism, characterized in that the evaporative cooling system comprises:

[0055] Cooling mechanism;

[0056] An overhead pressure control mechanism, the overhead pressure control mechanism comprising a pressure control body and a partition plate disposed in the pressure control body and dividing the space of the pressure control body into two independent pressure control spaces and a pressure stabilizing space, the partition plate being configured to be able to move up and down according to the air pressure of the pressure control space and the pressure stabilizing space;

[0057] The exhaust mechanism includes a first switch element, which is arranged on the air inlet side of the pressure control space and connected to the exhaust side of the cooling mechanism.

[0058] Solution 2. The evaporative cooling system according to Solution 1 is characterized in that the exhaust mechanism also includes a second switching element, and the second switching element is arranged on the exhaust side of the pressure controlled space.

[0059] Solution 3. The evaporative cooling system according to Solution 2 is characterized in that the exhaust mechanism also includes a vacuum pump, and the vacuum pump is connected to the second switching element.

[0060] Solution 4. The evaporative cooling system according to Solution 1 is characterized in that the exhaust mechanism also includes a third switch element, and the third switch element is arranged on the drainage side of the pressure controlled space.

[0061] Solution 5. The evaporative cooling system according to Solution 4 is characterized in that the third switch element is connected to the liquid inlet side of the cooling mechanism.

[0062] Solution 6. The evaporative cooling system according to Solution 1 is characterized in that the overhead pressure control mechanism also includes a limiting structure, which is arranged in the pressure control space and is configured to limit the movement of the partition plate.

[0063] Solution 7. The evaporative cooling system according to Solution 1 is characterized in that the cooling mechanism also includes a liquid return pipe, a liquid collecting ring pipe, an air collecting ring pipe, an air outlet pipe, a condenser, a connecting pipe, a pressure equalizing pipe and a fourth switch element, and the liquid return pipe, the liquid collecting ring pipe, the air collecting ring pipe, the air outlet pipe, the condenser, the connecting pipe, the pressure equalizing pipe and the fourth switch element are connected in sequence; the pressure equalizing pipe is connected to the first switch element.

[0064] Solution 8. A control method for an evaporative cooling system including an overhead pressure control mechanism, characterized in that the evaporative cooling system includes a cooling mechanism, an overhead pressure control mechanism and an exhaust mechanism, wherein the overhead pressure control mechanism includes a pressure control body and a partition plate arranged in the pressure control body and dividing the space of the pressure control body into two independent pressure control spaces and a pressure stabilizing space, wherein the partition plate is arranged to be able to move up and down according to the air pressure of the pressure control space and the pressure stabilizing space; an exhaust mechanism, wherein the exhaust mechanism includes a first switch element, which is arranged on the air inlet side of the pressure control space and connected to the exhaust side of the cooling mechanism; the control method includes:

[0065] Acquiring the operating state of the generator, wherein the operating state includes a working state and a stop intermittent state;

[0066] When the generator is in an operating state, the first switch element is controlled to remain in an open state.

[0067] Solution 9. The control method according to Solution 8 is characterized in that when the overhead pressure control mechanism further includes a second switch element arranged on the exhaust side of the pressure control space, the step of "controlling the first switch element to remain in an open state" also includes:

[0068] The second switch element is controlled to remain in a closed state.

[0069] Solution 10. The control method according to Solution 8 is characterized in that when the top pressure control mechanism further includes a third switch element arranged on the liquid discharge side of the pressure control space, the step of "controlling the first switch element to remain in an open state" also includes:

[0070] The third switch element is controlled to remain in an open state.

[0071] Solution 11. The control method according to Solution 8, characterized in that the control method further comprises:

[0072] When the generator is in an intermittent stop state, obtaining a first current air pressure on the exhaust side of the cooling mechanism;

[0073] Comparing the first current air pressure with the first preset air pressure;

[0074] When the first current air pressure is greater than or equal to a first preset air pressure, the exhaust mechanism is controlled to perform an exhaust operation.

[0075] Solution 12. The control method according to Solution 11 is characterized in that when the overhead pressure control mechanism further includes a second switch element arranged on the exhaust side of the pressure control space and a vacuum pump connected to the second switch element, the specific steps of "controlling the exhaust mechanism to perform the exhaust operation" include:

[0076] When the first current air pressure is greater than or equal to the first preset air pressure, the first switch element is closed, the second switch element is opened, and the vacuum pump is controlled to start running;

[0077] Acquire a second current air pressure of the pressure-controlled space;

[0078] comparing the second current air pressure with the second preset air pressure;

[0079] When the second current air pressure is lower than the second preset air pressure, the second switch element is first closed and the vacuum pump is controlled to stop working, and then the first switch element is opened.

[0080] Solution 13. The control method according to Solution 12 is characterized in that after the step of “turning on the first switch element”, the method further comprises:

[0081] Then, obtaining a second current air pressure of the pressure-controlled space;

[0082] comparing the second current air pressure with a third preset air pressure;

[0083] When the second current air pressure is greater than or equal to the third preset air pressure, controlling the exhaust mechanism to perform the exhaust operation again;

[0084] Wherein, the third preset air pressure is greater than the second preset air pressure.

[0085] Solution 14. The control method according to Solution 13 is characterized in that after the step of "controlling the exhaust mechanism to perform the exhaust operation", it also includes:

[0086] After the exhaust mechanism is controlled to perform the exhaust operation, the accumulated exhaust times of the exhaust operation are obtained;

[0087] Comparing the accumulated exhaust times with a preset exhaust times;

[0088] When the accumulated exhaust times is greater than or equal to a preset exhaust times, the exhaust mechanism is controlled to stop the exhaust operation.

[0089] Solution 15. The control method according to Solution 13 is characterized in that after the step of "controlling the exhaust mechanism to perform the exhaust operation", it also includes:

[0090] After controlling the exhaust mechanism to perform an exhaust operation, obtaining a first current air pressure on an exhaust side of the cooling mechanism;

[0091] comparing the first current air pressure with the first preset air pressure;

[0092] When the first current air pressure is less than the first preset air pressure, the exhaust mechanism is controlled to stop the exhaust operation.

[0093] Solution 16. The control method according to Solution 13 is characterized in that after the step of "controlling the exhaust mechanism to perform the exhaust operation", it also includes:

[0094] After the exhaust mechanism is controlled to perform the exhaust operation, the generator is in a working state;

[0095] When the generator is in operation, the exhaust mechanism is controlled to stop exhaust operation.

[0096] Solution 17. The control method according to any one of solutions 14 to 16 is characterized in that the step of "controlling the exhaust mechanism to stop exhaust operation" specifically includes:

[0097] The first switch element is opened, the second switch element is closed, and the vacuum pump is controlled to stop working.

[0098] Solution 18. The control method according to Solution 17 is characterized in that when the overhead pressure control mechanism further includes a third switch element disposed on the liquid discharge side of the pressure control body, after the step of “opening the first switch element, closing the second switch element, and controlling the vacuum pump to stop working”, it also includes:

[0099] The third switching element is turned on.

[0100] Solution 19. The control method according to Solution 13 is characterized in that when the overhead pressure control mechanism further includes a third switch element disposed on the liquid discharge side of the pressure control body, before the step of “closing the first switch element, opening the second switch element, and controlling the vacuum pump to start operation”, it also includes:

[0101] Turning off the third switching element; and

[0102] The step of “opening the first switch element” further includes:

[0103] The third switching element is turned on.

[0104] It will be understood by those skilled in the art that the evaporative cooling system of the present application including a top-mounted pressure control mechanism divides the space of the pressure control body into a pressure-stabilizing space and a pressure control space with adjustable space size by arranging a movable partition plate in the pressure control body, and the pressure control space is connected to the exhaust side of the cooling mechanism, so that the exhaust side of the cooling mechanism can enter the pressure control space through the first switching element when the generator encounters a sudden load change or a cooling mechanism failure causes gas accumulation, and the size of the pressure control space can be adaptively adjusted according to the air pressure on the exhaust side of the cooling mechanism, thereby effectively reducing the air pressure on the exhaust side of the cooling mechanism, improving the cooling effect of the stator wire rods, and reducing the flow phase difference between the inlet and outlet of the stator wire rods, thereby avoiding self-sustaining oscillation of the evaporative cooling system and ensuring the safe and stable operation of the generator.

[0105] Furthermore, by arranging a second switch element on the exhaust side of the pressure control space, it is beneficial to discharge the gas in the pressure control space, thereby ensuring that the top pressure control mechanism can continue to effectively regulate the gas pressure on the exhaust side of the cooling mechanism in subsequent processes.

[0106] Furthermore, by connecting the second switch element to the vacuum pump, the pressure-controlled space is brought into a low-pressure state, thereby facilitating the gas on the exhaust side of the cooling mechanism to flow to the pressure-controlled space.

[0107] Furthermore, by arranging a third switch element on the liquid inlet side of the cooling mechanism, the third switch element is connected to the liquid inlet side of the cooling mechanism, which helps to return the working fluid entering the pressure control space with the gas to the cooling mechanism through the drain valve.

[0108] Furthermore, by providing a limiting structure in the pressure control space, the movement range of the partition plate can be effectively limited, thereby ensuring the stability of the pressure control space and the normal operation of the system.

[0109] It can be understood by those skilled in the art that the control method of the evaporative cooling system of the present application controls the first switch element to remain in an open state when the generator is in working state, so that when the generator encounters a sudden load change or a cooling mechanism failure causes gas accumulation on the exhaust side of the cooling mechanism, the gas is automatically guided into the pressure controlled space, thereby effectively avoiding a sudden increase in air pressure on the exhaust side of the cooling mechanism, thereby ensuring the cooling effect of the stator wire rods, reducing the flow phase difference between the inlet and outlet of the stator wire rods, avoiding the risk of self-sustaining oscillation, and ensuring stable and efficient operation of the generator.

[0110] Furthermore, by closing the second switch element while opening the first switch element, the working fluid that enters the pressure control space along with the gas can be effectively prevented from being lost from the exhaust side of the cooling mechanism, thereby saving working fluid and avoiding waste.

[0111] Furthermore, by opening the third switch element while opening the first switch element, the working medium entering the control space along with the gas is facilitated to flow back to the cooling mechanism from the drain side of the cooling mechanism.

[0112] Furthermore, when the generator is in a stop intermittent state, by closing the first switch element, opening the second switch element, and controlling the vacuum pump to start operation when the first current air pressure is greater than or equal to the first preset air pressure, it is helpful to discharge the non-condensable gas accumulated in the pressure control space. When the second current air pressure is less than the second preset air pressure, closing the second switch element, controlling the vacuum pump to stop working, and opening the first switch element, it is helpful for the gas on the exhaust side of the cooling mechanism to enter the pressure control space.

[0113] Furthermore, when the generator is in an intermittent state, by obtaining the cumulative exhaust times of the exhaust operation and comparing it with the preset exhaust times, when the cumulative exhaust times are greater than or equal to the preset exhaust times, it means that the gas accumulated on the exhaust side of the cooling mechanism has been effectively exhausted. At this time, the exhaust mechanism is controlled to stop the exhaust operation, which can avoid waste of resources. In other words, when the cumulative exhaust times are less than the preset exhaust times, the exhaust mechanism is controlled to cycle the exhaust operation, which can effectively reduce the non-condensable gas content of the cooling mechanism. BRIEF DESCRIPTION OF THE DRAWINGS

[0114] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings, in which:

[0115] Figure 1 is a system diagram of the evaporative cooling system of the present invention;

[0116] Figure 2 is a flow chart of a control method of an evaporative cooling system of the present invention;

[0117] Figure 3 It is a logic diagram of a possible implementation method of the control method of the evaporative cooling system of the present invention.

[0118] List of reference numerals:

[0119] 1. Cooling mechanism; 101. Liquid return pipe; 102. Liquid collecting ring pipe; 103. Gas collecting ring pipe; 104. Gas outlet pipe; 105. Condenser; 106. Connecting pipe; 107. Pressure equalizing pipe; 108. Second exhaust valve; 2. Overhead pressure control mechanism; 201. Pressure control space; 202. Pressure stabilizing space; 203. Limiting device; 204. Partition plate; 3. Exhaust mechanism; 301. Inlet valve; 302. Liquid discharge valve; 303. First exhaust valve; 304. Inlet pipe; 305. Liquid discharge pipe; 306. Exhaust pipe; 307. Vacuum pump; 4. Stator wire rod. DETAILED DESCRIPTION

[0120] The preferred embodiments of the present application are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present application and are not intended to limit the protection scope of the present application.

[0121] It should be noted that, in the description of the present application, terms such as "upper", "lower", "inner", "bottom", "end" and the like indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is merely for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be understood as a limitation on the present application.

[0122] In addition, it should be noted that in the description of this application, unless otherwise clearly specified and limited, the terms "disposed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium, or it can be the internal connection of two elements. For those skilled in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0123] First refer to Figure 1 , the evaporative cooling system of the present application is described.

[0124] In order to solve the problem that the evaporative cooling system is prone to self-sustaining oscillation when the load suddenly increases or the cooling mechanism 1 fails, the evaporative cooling system of the present application includes a cooling mechanism 1, an overhead pressure control mechanism 2 and an exhaust mechanism 3. Among them, the overhead pressure control mechanism 2 includes a pressure control body and a partition plate 204 arranged in the pressure control body and dividing the space of the space body into two independent pressure control spaces 201 and pressure stabilizing spaces 202, and the partition plate 204 is arranged to be able to move up and down according to the air pressure bands of the pressure control space 201 and the pressure stabilizing space 202. The exhaust mechanism 3 includes a first switch element, which is arranged on the air inlet side of the pressure control space 201 and connected to the exhaust side of the cooling mechanism 1.

[0125] The present application divides the space of the pressure control body into a pressure stabilizing space 202 with adjustable space size and a pressure control space 201 by setting a movable partition plate 204 in the pressure control body. The pressure control space 201 is connected to the exhaust side of the cooling mechanism 1, so that the exhaust side of the cooling mechanism 1 can enter the pressure control space 201 through the first switching element when the generator encounters a sudden load change or a failure of the cooling mechanism 1 causes gas accumulation, and the size of the pressure control space 201 can be adaptively adjusted according to the air pressure on the exhaust side of the cooling mechanism 1, thereby effectively avoiding a sudden increase in air pressure on the exhaust side of the cooling mechanism 1, stabilizing the cooling effect of the stator wire rod 4, and reducing the flow phase difference between the inlet and outlet of the stator wire rod, thereby avoiding self-sustaining oscillation of the evaporative cooling system and ensuring safe and stable operation of the generator.

[0126] See below for further reference Figure 1 , a preferred implementation of the evaporative cooling system of the present application is introduced. Those skilled in the art will understand that the implementation described below is only used to illustrate the principle of the present application and is not intended to limit the scope of protection of the present application. On the premise that the evaporative cooling system at least includes a cooling mechanism 1, an overhead pressure control mechanism 2 and an exhaust mechanism 3, those skilled in the art can adjust the following settings so that the present application can be applied to more specific application scenarios.

[0127] like Figure 1 As shown, the evaporative cooling system includes a cooling mechanism 1, a top pressure control mechanism 2 and an exhaust mechanism 3. The cooling mechanism 1 includes a liquid return pipe 101, a liquid collecting ring pipe 102, a gas collecting ring pipe 103, an exhaust pipe 104, a condenser 105, a connecting pipe 106, a pressure equalizing pipe 107 and a fourth switch element connected in sequence. The fourth switch element is a second exhaust valve 108. In the above-mentioned setting, the liquid phase working medium flows into the stator wire rod 4 through the liquid return pipe 101 and the liquid collecting ring pipe 102, and the liquid phase working medium absorbs the heat of the stator wire rod 4 and becomes a gas phase / gas-liquid two-phase working medium and flows out of the stator wire rod, through the gas collecting ring pipe 103 and the exhaust pipe 104 to the condenser 105, releases heat in the condenser 105 and becomes a liquid phase working medium, enters the next cycle, and realizes the cooling of the stator wire rod 4. In this process, the connecting pipe 106, the pressure equalizing pipe 107 and the second exhaust valve 108 are used to discharge the gas accumulated in the condenser 105.

[0128] It should be noted that the evaporative cooling system uses the boiling process of the working fluid to bring heat out of the stator wire rods. Since the condenser 105 is an important component for the working fluid to release heat and become a liquid phase, and the pressure equalizing tube 107 is connected to the condenser 105, and the pressure equalizing tube 107 plays a role in balancing the system pressure, the non-condensable gas gathers here. The presence of these non-condensable gases will reduce the heat dissipation efficiency of the cooling mechanism 1. Although the second exhaust valve 108 is designed in the cooling mechanism 1 to discharge the non-condensable gas, it mainly plays a role during the initial operation. Once the system is running stably, due to the continuous circulation of the working fluid, it is difficult for the second exhaust valve 108 to continuously and effectively remove the non-condensable gas in the pressure equalizing tube 107, and it may also cause waste of the working fluid during the exhaust process, thereby affecting the performance of the cooling mechanism 1.

[0129] It should also be noted that the present application has no limitation on the specific configuration of the second exhaust valve 108, as long as it can play a role of conducting or blocking. For example, the second exhaust valve 108 can be a second exhaust electric valve or a second exhaust solenoid valve.

[0130] It should also be noted that the present application has no restriction on the number of condensers 105, as long as the gas phase working medium can be converted into a liquid phase working medium through the condenser 105. For example, the number of condensers 105 is 1, 2, or other numbers. When the number of condensers 105 is 2 or more, these condensers 105 are arranged in parallel and are all connected to the pressure equalizing tube 107 to avoid that when a certain condenser 105 fails, other condensers 105 can still condense the gas phase working medium.

[0131] See next Figure 1 , the top pressure control mechanism 2 includes a pressure control body and a partition plate 204. The partition plate 204 is arranged in the pressure control body and divides the space of the space body into two independent pressure control spaces 201 and pressure stabilizing spaces 202. The partition plate 204 can move up and down according to the air pressure of the pressure control space 201 and the pressure stabilizing space 202. Specifically, the pressure control space 201 is connected to the pressure equalizing tube 107, so that the gas in the pressure equalizing tube 107 can enter the pressure control space 201. As the gas enters the pressure control space 201, the air pressure in the pressure control space 201 gradually increases. When the air pressure of the pressure control space 201 is greater than the air pressure of the pressure stabilizing space 202, the partition plate can move upward.

[0132] See next Figure 1The top pressure control mechanism 2 also includes a limiting structure 203, which is arranged in the pressure control space 201 and can effectively limit the movement range of the partition plate 204, thereby ensuring the stability of the pressure control space 201 and the normal operation of the system. Specifically, the limiting structure 203 is arranged in the pressure control space 201, and when the partition plate 204 moves due to the difference in air pressure, the limiting structure 203 can prevent the partition plate 204 from moving excessively, thereby avoiding excessive fluctuations in the air pressure in the pressure control space 201.

[0133] It should be noted that the present application has no limitation on the specific arrangement of the limiting structure 203, as long as it can limit the movement range of the partition plate 204. For example, the limiting structure 203 can be a limiting block arranged on the inner wall of the pressure control space 201, and the limiting block can be arranged around the inner wall of the pressure control space 201.

[0134] See next Figure 1 , an air inlet, an exhaust port and a liquid discharge port are arranged on the pressure control body corresponding to the pressure control space 201. The exhaust mechanism 3 includes a first switch element, an air inlet pipe 304, a second switch element, an exhaust pipe 306, a third switch element, a liquid discharge pipe 305 and a vacuum pump 307. Among them, the first switch element is an air inlet valve 301, the second switch element is a first exhaust valve 303, and the third switch element is a liquid discharge valve 302. One end of the air inlet pipe 304 is connected to the air inlet, and the other end is connected to the exhaust side of the cooling mechanism 1. Among them, the equalizing tube 107 serves as the exhaust side of the cooling mechanism 1, and can make the gas in the equalizing tube 107 enter the pressure control space 201 through the air inlet pipe 304. An air inlet valve 301 is arranged on the air inlet pipe 304. As a first switch element, the air inlet valve 301 can conduct or block the connection between the cooling mechanism 1 and the pressure control space 201. One end of the exhaust pipe 306 is connected to the exhaust port, and the other end is connected to the vacuum pump 307, which is conducive to the vacuum pump 307 to extract the gas in the pressure control space 201, so that the pressure control space 201 maintains a negative pressure state, which is conducive to the gas in the equalizing tube 107 entering the pressure control space 201. The exhaust pipe 306 is provided with a first exhaust valve 303, which, as a second switch element, can control the discharge of the gas in the pressure control space 201. One end of the drain pipe 305 is connected to the exhaust port, and the other end is connected to the return pipe 101 of the cooling mechanism 1, which can effectively prevent the loss of the working medium carried by the gas entering the pressure control space 201, and ensure that the liquid phase working medium can smoothly flow back to the cooling mechanism 1 through the drain pipe 305. The drain pipe 305 is provided with a drain valve 302, which, as a third switch element, can control the flow of the liquid phase working medium in the pressure control space 201.

[0135] It should be noted that the present application has no restrictions on the specific configuration of the intake valve 301, the first exhaust valve 303 and the drain valve 302, as long as they can play the role of conduction or blocking. For example, the intake valve 301 can be an intake electric valve or an intake solenoid valve. And / or, the first exhaust valve 303 can be a first exhaust electric valve or a first exhaust solenoid valve. And / or, the drain valve 302 can be a drain electric valve or a drain solenoid valve.

[0136] like Figure 2 As shown, based on the above configuration, the control method of the evaporative cooling system of the present application includes:

[0137] S101, obtaining the operating state of the generator, where the operating state includes a working state and a stop intermittent state;

[0138] S102: When the generator is in operation, control the first switch element to remain in an open state.

[0139] It should be noted that when the generator is in operation, if there is a sudden increase in the load on the generator or a failure in the parallel condenser 105 in the cooling mechanism 1, the gas in the pressure equalizing tube 107 increases, causing the gas pressure to increase. By controlling the first switch element to remain in the open state, the gas in the cooling mechanism 1 can enter the pressure control space 201. When the gas pressure in the pressure control space 201 gradually increases, and when the gas pressure in the pressure control space 201 is greater than the gas pressure in the pressure stabilizing space 202, the partition plate 204 moves upward, so that the top pressure control mechanism 2 can adaptively adjust the position of the partition plate 204 according to the gas pressure in the cooling mechanism 1, so that the cooling mechanism 1 can operate stably and avoid self-sustaining oscillation.

[0140] The following is an introduction to a preferred implementation of a control method for an evaporative cooling system including an overhead pressure control mechanism of the present application.

[0141] In one embodiment, when the overhead pressure control mechanism further includes a second switch element disposed on the exhaust side of the pressure control space, the step of "controlling the first switch element to remain in an open state" also includes: controlling the second switch element to remain in a closed state.

[0142] For example, the first switch element is the intake valve 301, and the second switch element is the first exhaust valve 303. When the generator is in operation, the intake valve 301 is controlled to remain in an open state, while the first exhaust valve 303 is controlled to remain in a closed state, so that the gas on the exhaust side of the cooling mechanism 1 can enter the pressure control space 201, while preventing the working fluid entering the pressure control space with the gas from being lost through the first exhaust valve 303.

[0143] In one embodiment, when the overhead pressure control mechanism further includes a third switch element disposed on the liquid discharge side of the pressure control space, the step of "controlling the first switch element to remain in an open state" also includes:

[0144] The third switch element is controlled to remain in an open state.

[0145] For example, the first switch element is the air intake valve 301, and the third switch element is the drain valve 302. When the generator is in operation, the air intake valve 301 is controlled to remain in an open state, and the drain valve 302 is controlled to remain in an open state, so that the gas on the exhaust side of the cooling mechanism 1 can enter the pressure control space 201, and the working fluid entering the pressure control space 201 with the gas can flow back to the cooling mechanism 1 through the drain valve 302.

[0146] In one embodiment, the control method further includes:

[0147] When the motor is in an intermittent stop state, obtaining a first current air pressure on the exhaust side of the cooling mechanism 1;

[0148] Comparing the first current air pressure with the first preset air pressure;

[0149] When the first current air pressure is greater than or equal to the first preset air pressure, the exhaust mechanism 3 is controlled to perform an exhaust operation.

[0150] For example, the pressure equalizing tube 107 is used as the exhaust side of the cooling mechanism 1. When the generator is in an intermittent state, the first current air pressure of the pressure equalizing tube 107 is obtained, and the first current air pressure is compared with the first preset air pressure. When the first current air pressure is greater than or equal to the first preset air pressure, it means that the air pressure on the exhaust side of the cooling mechanism 1 is relatively large, and the exhaust mechanism 3 is controlled to perform the exhaust operation.

[0151] Further, when the top pressure control mechanism includes a second switch element disposed on the exhaust side of the pressure control space 201 and a vacuum pump 307 connected to the second switch element, the specific steps of the exhaust operation include:

[0152] When the first current air pressure is greater than or equal to the first preset air pressure, the first switch element is closed, the second switch element is opened, and the vacuum pump 307 is controlled to start running;

[0153] Acquire a second current air pressure of the pressure-controlled space 201;

[0154] Comparing the second current air pressure with the second preset air pressure;

[0155] When the second current air pressure is lower than the second preset air pressure, the second switch element is first closed and the vacuum pump 307 is controlled to stop working, and then the first switch element is opened.

[0156] It should be noted that when a large amount of gas is gathered in the pressure-equalizing tube 107, in order to facilitate the introduction of the gas in the pressure-equalizing tube 107 into the overhead pressure control mechanism 2, the first switch element can be closed first, the second switch element can be opened, and the vacuum pump 307 can be controlled to start running at the same time, so that the pressure-controlled space 201 is in a negative pressure state. When the second current air pressure of the pressure-controlled space 201 is less than the second preset air pressure, it means that the gas pressure in the pressure-controlled space 201 is low. At this time, the second switch element is closed first and the vacuum pump 307 is controlled to stop working, and then the first switch element is opened, which is conducive to the gas in the pressure-equalizing tube 107 entering the pressure-controlled space 201.

[0157] For example, the first switch element is the intake valve 301, and the second switch element is the first exhaust valve 303. When the generator is in an intermittent state, the intake valve 301 is closed, the first exhaust valve 303 is opened, and the vacuum pump 307 is controlled to start, so that the pressure control space 201 is in a negative pressure state. Then the second current air pressure of the pressure control space 201 is obtained and compared with the second preset air pressure. When the second current air pressure is less than the second preset air pressure, it means that the air pressure of the pressure control space 201 is low. At this time, the first exhaust valve 303 is closed and the vacuum control stops working, and then the intake valve 301 is opened, which is conducive to the gas in the pressure equalizing tube 107 to enter the pressure control space 201, thereby reducing the gas accumulation in the cooling mechanism 1.

[0158] Furthermore, when the evaporative cooling system further includes a third switch element disposed on the liquid discharge side of the pressure control body, before the step of “closing the first switch element, opening the second switch element, and controlling the vacuum pump 307 to start operation”, the following steps are also included:

[0159] closing the third switching element; and

[0160] The step of “opening the first switch element” further includes:

[0161] The third switching element is opened.

[0162] For example, the first switch element is the air intake valve 301, the second switch element is the first exhaust valve 303, and the third switch element is the drain valve 302. Before the steps of closing the air intake valve 301, opening the first exhaust valve 303, and controlling the vacuum pump 307 to start operation, the drain valve 302 is closed to prevent the working fluid in the cooling mechanism 1 from entering the pressure control space 201 through the drain valve 302, thereby affecting the vacuum pump 307. In addition, after the step of opening the air intake valve 301, the drain valve 302 is opened, which is conducive to the working fluid entering the pressure control space 201 with the gas to flow back to the cooling mechanism 1 through the drain valve 302, thereby avoiding the waste of working fluid.

[0163] Further, after the step of “opening the first switch element”, the step further includes:

[0164] Then, the second current air pressure of the pressure control space 201 is obtained;

[0165] comparing the second current air pressure with the third preset air pressure;

[0166] When the second current air pressure is greater than or equal to the third preset air pressure, controlling the exhaust mechanism to perform the exhaust operation again;

[0167] The third preset air pressure is greater than the second preset air pressure.

[0168] For example, the first switch element is the intake valve 301, the second switch element is the first exhaust valve 303, and the exhaust side of the cooling mechanism 1 is the equalizing tube 107. When the first exhaust valve 303 is closed, the vacuum pump 307 stops working, and the intake valve 301 is opened, the gas in the pressure control space 201 gradually increases, and the air pressure also increases accordingly. When the second current air pressure in the pressure control space 201 is greater than or equal to the third preset air pressure, it means that the pressure control space 201 is large enough and the air pressure is also relatively large. The speed at which the gas in the equalizing tube 107 flows to the pressure control space 201 is relatively slow. At this time, it is necessary to discharge the non-condensable gas in the pressure control space 201 to reduce the size and pressure of the pressure control space 201. Therefore, the exhaust mechanism 3 is controlled to perform the exhaust operation again.

[0169] In one embodiment, the step of "controlling the exhaust mechanism to perform the exhaust operation" further includes:

[0170] After the exhaust mechanism is controlled to perform the exhaust operation, the accumulated exhaust times of the exhaust operation are obtained;

[0171] Compare the accumulated exhaust times with the preset exhaust times;

[0172] When the accumulated exhaust times are greater than or equal to the preset exhaust times, the exhaust mechanism is controlled to stop the exhaust operation.

[0173] It should be noted that in order to effectively reduce the non-condensable gas content of the cooling mechanism, the exhaust mechanism needs to perform exhaust operations in multiple cycles. By controlling the exhaust mechanism to perform multiple exhaust operations, the gas accumulated on the exhaust side of the cooling mechanism can be effectively discharged. At this time, controlling the exhaust mechanism to stop the exhaust operation can avoid waste of resources.

[0174] For example, after the exhaust mechanism is controlled to perform the exhaust operation, the cumulative exhaust times of the exhaust operation are obtained. When the cumulative exhaust times are greater than or equal to the preset exhaust times, it means that the gas accumulated on the exhaust side of the cooling mechanism has been effectively exhausted. At this time, the exhaust mechanism is controlled to stop the exhaust operation. When the cumulative exhaust times are less than the preset exhaust times, it can be considered that the gas accumulated on the exhaust side of the cooling mechanism has not been effectively exhausted. Therefore, the exhaust mechanism is controlled to cyclically perform the exhaust operation, which can effectively reduce the non-condensable gas content of the cooling mechanism.

[0175] In one embodiment, the step of "controlling the exhaust mechanism to perform the exhaust operation" further includes:

[0176] After the exhaust mechanism is controlled to perform the exhaust operation, a first current air pressure on the exhaust side of the cooling mechanism is obtained;

[0177] Comparing the first current air pressure with the first preset air pressure;

[0178] When the first current air pressure is less than the first preset air pressure, the exhaust mechanism is controlled to stop the exhaust operation.

[0179] For example, after the exhaust mechanism is controlled to perform the exhaust operation, the first current air pressure on the exhaust side of the cooling mechanism is obtained. When the first current air pressure is less than the first preset air pressure, it means that the gas accumulated on the exhaust side of the cooling mechanism has been effectively exhausted. At this time, the exhaust mechanism is controlled to stop the exhaust operation. When the first current air pressure is greater than or equal to the first preset air pressure, it means that a large amount of gas is still accumulated on the exhaust side of the cooling mechanism. Therefore, the exhaust mechanism is controlled to circulate the exhaust operation, which can effectively reduce the non-condensable gas content of the cooling mechanism.

[0180] In one embodiment, the step of "controlling the exhaust mechanism to perform the exhaust operation" further includes:

[0181] After the exhaust mechanism is controlled to perform the exhaust operation, the generator is in a working state;

[0182] When the generator is in operation, the exhaust mechanism is controlled to stop the exhaust operation.

[0183] It should be noted that the exhaust operation is only performed when the generator is in an intermittent state. When the generator is in an operating state, the exhaust mechanism needs to be controlled to stop the exhaust operation.

[0184] For example, after the exhaust mechanism is controlled to perform the exhaust operation, the working state of the generator is obtained. When the generator is in the working state, the exhaust mechanism is controlled to stop the exhaust operation. When the generator is still in the intermittent state of stopping, the exhaust mechanism needs to be controlled to cyclically perform the exhaust operation, which can effectively reduce the non-condensable gas content of the cooling mechanism.

[0185] Furthermore, the step of “controlling the exhaust mechanism to stop the exhaust operation” specifically includes:

[0186] The first switch element is opened, the second switch element is closed, and the vacuum pump is controlled to stop working.

[0187] For example, the first switch element is an intake valve and the second switch element is a first exhaust valve. When the accumulated exhaust times of the exhaust operation is greater than or equal to the preset exhaust times, or the first current air pressure is less than the first preset air pressure, or the generator is in a working state, the intake valve is opened, the first exhaust valve is closed, and the vacuum pump is controlled to stop working, thereby stopping the exhaust operation of the exhaust mechanism.

[0188] Furthermore, when the overhead pressure control mechanism further includes a third switch element disposed on the liquid discharge side of the pressure control body, after the step of “opening the first switch element, closing the second switch element, and controlling the vacuum pump to stop working”, the following steps are further included:

[0189] The third switching element is opened.

[0190] For example, the first switch element is the air intake valve 301, the second switch element is the first exhaust valve 303, and the third switch element is the drain valve 302. After the air intake valve 301 is opened, the first exhaust valve 303 is closed, and the vacuum pump 307 is controlled to stop working, the drain valve 302 is opened, so that the working medium in the pressure control space 201 flows back to the cooling mechanism through the drain valve 302.

[0191] Combine the following Figure 3 , a possible operation process of the control method of the evaporative cooling system of the present application is briefly described. Figure 3 The following is a logic diagram of a possible implementation of a control method for an evaporative cooling system of the present application.

[0192] S201. Obtain the operating status of the generator, and then execute S202.

[0193] S202: Determine whether the generator is in operation. If yes, execute S203; otherwise, execute S204.

[0194] S203, opening the air intake valve 301 and the liquid discharge valve 302, and closing the first exhaust valve 303 at the same time.

[0195] S204, obtaining the first current air pressure in the pressure equalizing tube 107, and then executing S205.

[0196] S205: Determine whether the first current air pressure is greater than or equal to the first preset air pressure. If yes, execute S206; otherwise, execute S212.

[0197] S206, close the air intake valve 301 and the liquid discharge valve 302, open the first exhaust valve 303, and control the vacuum pump 307 to start running, and then execute S207.

[0198] S207, obtaining the second current air pressure of the pressure control space 201, and then executing S208.

[0199] S208: Determine whether the second current air pressure is less than the second preset air pressure. If yes, execute S209; otherwise, execute S207.

[0200] S209, first close the first exhaust valve 303 and control the vacuum pump 307 to stop working, then open the air intake valve 301, and finally open the drain valve 302, and then execute S210.

[0201] S210, obtaining the cumulative number of exhaust times of the exhaust operation, and then executing S211.

[0202] S211, determine whether the cumulative exhaust times is greater than or equal to the preset exhaust times. If yes, execute S212; otherwise, execute S213.

[0203] S212, open the air intake valve 301 and the liquid discharge valve 302, close the first exhaust valve 303, and control the vacuum pump 307 to stop working.

[0204] S213, then obtain the working status of the generator, and then execute S214.

[0205] S214: Determine whether the generator is in working state. If yes, execute S212; otherwise, execute S215.

[0206] S215, obtaining the first current air pressure on the exhaust side of the cooling mechanism 1, and then executing S216.

[0207] S216, determining whether the first current air pressure is less than the first preset air pressure; if so, executing S212, otherwise executing S217.

[0208] S217, obtaining the second current air pressure of the pressure control space 201, and then executing S218.

[0209] S218: Determine whether the second current air pressure is greater than or equal to the third preset air pressure. If yes, execute S206; otherwise, execute S210.

[0210] Those skilled in the art will appreciate that, although some embodiments described herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present application and form different embodiments. For example, in the claims of the present application, any one of the claimed embodiments may be used in any combination.

[0211] So far, the technical solutions of the present application have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present application is obviously not limited to these specific embodiments. Without departing from the principles of the present application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present application.

Claims

1. An evaporative cooling system comprising an overhead pressure control mechanism, characterized in that: The evaporative cooling system comprises: Cooling mechanism; An overhead pressure control mechanism, the overhead pressure control mechanism comprising a pressure control body and a partition plate disposed in the pressure control body and dividing the space of the pressure control body into two independent pressure control spaces and a pressure stabilizing space, the partition plate being configured to be able to move up and down according to the air pressure of the pressure control space and the pressure stabilizing space; The exhaust mechanism includes a first switch element, which is arranged on the air inlet side of the pressure control space and connected to the exhaust side of the cooling mechanism.

2. The evaporative cooling system according to claim 1, characterized in that: The exhaust mechanism further includes a second switch element, which is disposed on the exhaust side of the pressure control space.

3. The evaporative cooling system according to claim 2, characterized in that: The exhaust mechanism further includes a vacuum pump connected to the second switching element.

4. The evaporative cooling system according to claim 1, characterized in that The exhaust mechanism further includes a third switch element, and the third switch element is arranged on the discharge side of the pressure control space.

5. The evaporative cooling system according to claim 4, characterized in that The third switch element is connected to the liquid inlet side of the cooling mechanism.

6. The evaporative cooling system according to claim 1, characterized in that The top pressure control mechanism further includes a limiting structure, which is disposed in the pressure control space and is configured to limit the movement of the partition plate.

7. The evaporative cooling system according to claim 1, characterized in that The cooling mechanism also includes a liquid return pipe, a liquid collecting ring pipe, a gas collecting ring pipe, an air outlet pipe, a condenser, a connecting pipe, a pressure equalizing pipe and a fourth switch element. The liquid return pipe, the liquid collecting ring pipe, the gas collecting ring pipe, the air outlet pipe, the condenser, the connecting pipe, the pressure equalizing pipe and the fourth switch element are connected in sequence; the pressure equalizing pipe is connected to the first switch element.

8. A control method for an evaporative cooling system including an overhead pressure control mechanism, characterized in that: The evaporative cooling system comprises a cooling mechanism, an overhead pressure control mechanism and an exhaust mechanism, wherein the overhead pressure control mechanism comprises a pressure control body and a partition plate arranged in the pressure control body and dividing the space of the pressure control body into two independent pressure control spaces and a pressure stabilizing space, wherein the partition plate is arranged to be able to move up and down according to the air pressure of the pressure control space and the pressure stabilizing space; an exhaust mechanism, wherein the exhaust mechanism comprises a first switch element, which is arranged at the air inlet side of the pressure control space and connected to the exhaust side of the cooling mechanism; and the control method comprises: Acquiring the operating state of the generator, wherein the operating state includes a working state and a stop intermittent state; When the generator is in an operating state, the first switch element is controlled to remain in an open state.

9. The control method according to claim 8, characterized in that: When the overhead pressure control mechanism further includes a second switch element arranged on the exhaust side of the pressure control space, the step of "controlling the first switch element to remain in an open state" also includes: The second switch element is controlled to remain in a closed state.

10. The control method according to claim 8, characterized in that: When the overhead pressure control mechanism further includes a third switch element disposed on the liquid discharge side of the pressure control space, the step of "controlling the first switch element to remain in an open state" also includes: The third switch element is controlled to remain in an open state.

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