Compressed air pressurization pumped storage system and method

Abstract

According to the compressed air pressurization pumped storage system and method, pressure containers are arranged in a layered mode from top to bottom, and each layer comprises one or more communicated pressure containers. A liquid level sensor is arranged in the pressure container, a pressure detection device is arranged in the pressure container located on the lowermost layer, and the liquid level sensor and the pressure detection device are in signal connection with the controller. The pressure container is connected with an external water source through a water conveying pipeline, and water driving equipment is arranged on the water conveying pipeline. The top of the inner cavity of the pressure container is communicated through a gas pipeline, and a valve for controlling on-off of a gas path is arranged on the pipeline. The method comprises an energy storage stage and an energy release stage, the pressure container is filled with water from top to bottom in the energy storage stage, and the pressure container is drained from bottom to top in the energy release stage. According to the system and method provided by the invention, the energy storage density in unit space is improved, and the total pressure fluctuation at the inlet of the water turbine can be effectively stabilized.

Description

Technical Field

[0001] This invention relates to the field of power energy storage technology, and in particular to a compressed air pressurized pumped water storage system and method. Background Technology

[0002] Pumped storage technology, as a mature large-scale energy storage solution, plays a crucial role in power system peak shaving, frequency regulation, and backup power supply scenarios. Currently, traditional pumped storage systems face the following technical bottlenecks: Firstly, the system's energy storage capacity is highly dependent on the reservoir capacity and natural elevation difference, making it extremely limited by geographical conditions. Expanding energy storage requires substantial investment in new reservoirs, resulting in long construction periods and significant ecological impacts. Secondly, during charging and discharging, the pump head fluctuates dramatically, causing the equipment to operate under variable conditions for extended periods. This not only reduces energy storage efficiency but also exacerbates equipment wear and shortens its lifespan.

[0003] To overcome the above limitations, the industry has attempted to improve the performance of pumped hydro storage systems by coupling compressed air energy storage technology. However, existing coupling schemes have many shortcomings: First, gas storage often relies on a single pressure vessel and lacks a reasonable structural design, resulting in difficulty in pressure regulation and an inability to effectively suppress pump head fluctuations. Second, the energy conversion synergy between gas and liquid is poor, and the pressurization effect of compressed air is not fully utilized, resulting in limited energy storage improvement. Summary of the Invention

[0004] To address the technical problems in existing pumped-storage technologies, such as the difficulty in pressure regulation, the inability to effectively suppress pump head fluctuations, and the limited effectiveness of compressed air pressurization in improving energy storage, this invention provides a compressed air pressurized pumped-storage system and method.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A compressed air booster pumped water storage system includes: a pressure vessel, a water-driven device, an external water source, a liquid level sensor, a pressure detection device, and a controller; The pressure vessel is designed as a closed chamber structure, and the pressure vessels are arranged in layers from top to bottom; A liquid level sensor is installed inside the pressure vessel, and a pressure detection device is installed in the lowest layer of the pressure vessel. The liquid level sensor and the pressure detection device are connected to the controller signal. The bottom of the pressure vessel's inner cavity is connected to an external water source via a water supply pipe, and a water-driven device is installed on the water supply pipe. The top of the inner cavity of all pressure vessels is connected by gas pipelines, and each pipeline is equipped with a valve that controls the gas flow of each pressure vessel. The height of the upper part of the external water source is less than the height of the lower part of the lowest pressure vessel.

[0007] Furthermore, the water supply pipeline includes: a main water supply pipe and branch water supply pipes; An external water source is connected to one end of the main water supply pipe, and the other end of the main water supply pipe is connected to the bottom of the pressure vessel cavity through branch water supply pipes. A first valve is installed on the branch water supply pipe.

[0008] Furthermore, a pressure buffer tank is connected to the main water supply pipe.

[0009] Furthermore, the gas pipeline includes: a main gas pipe and branch gas pipes; The inner cavity of the pressure vessel is connected to the main gas pipe via gas branch pipes; A second valve is installed on the gas branch pipe.

[0010] Furthermore, each layer of pressure vessel is equipped with two gas branches; each gas branch is equipped with a one-way valve, and the one-way valves on the two gas branches are in opposite directions.

[0011] Furthermore, the water-driven device is a reversible water pump turbine.

[0012] Furthermore, the controller includes: The signal acquisition unit is used to acquire the real-time liquid level signal of the pressure vessel from the liquid level sensor, and to acquire the real-time pressure signal of the lowest pressure vessel from the pressure detection device. The analysis and processing unit is used to analyze the real-time liquid level value corresponding to the real-time liquid level signal, compare the real-time liquid level value with the preset liquid level high value and liquid level low value, and issue a first control signal when the real-time liquid level value is greater than the liquid level high value and issue a second control signal when the real-time liquid level value is lower than the liquid level low value; and to analyze the real-time pressure value corresponding to the real-time pressure signal, and issue a third control signal when the real-time pressure value is greater than the preset pressure threshold. The control unit is configured to acquire a first control signal and control the water-driven equipment to shut down and control the corresponding first valve on the current pressure vessel to shut down during the energy storage phase, thereby stopping the injection of water into the current pressure vessel; acquire a second control signal and control the corresponding first valve on the current pressure vessel to shut down during the energy release phase, thereby stopping the drainage of water from the current pressure vessel; and acquire a third control signal and control the water-driven equipment to shut down and control the corresponding first valve on the lowest pressure vessel to shut down during the energy storage phase, thereby stopping the injection of water into the lowest pressure vessel.

[0013] Furthermore, the height difference between any two adjacent pressure vessels is the same.

[0014] This invention provides a compressed air-pressurized pumped water storage method, which is based on a compressed air-pressurized pumped water storage system. The method comprises two stages: energy storage and energy release. The energy storage stage includes the following steps: Step S11. Set the gas in all pressure vessels to atmospheric pressure; Step S12. Turn on the water-driven equipment and inject water into the pressure vessels of each layer in order from top to bottom, compressing the gas layer by layer into the pressure vessel of the bottom layer in order from top to bottom; when the water injection of each layer of pressure vessel is completed, close the water and gas passage on that layer of pressure vessel. The energy release phase includes the following steps: Step S21. Open the water passage on the lowest pressure vessel, discharge the water in the pressure vessel to an external water source through the water pipeline and drive the power generation equipment to generate electricity until the water in the lowest pressure vessel is completely discharged. Step S22. Starting with the pressure vessel set on the second layer from bottom to top, drain the pressure vessels of each layer in order from bottom to top, and discharge the water in the pressure vessels one by one to the external water source through the water supply pipe to drive the power generation equipment to generate electricity; when draining, open the gas pipe between the pressure vessel being drained and the lowest pressure vessel until the water in all pressure vessels has been drained.

[0015] Furthermore, during the energy release phase, the drainage period of the pressure vessel in any layer partially overlaps with the drainage period of the pressure vessel in the adjacent upper layer.

[0016] The compressed air pressurized pumped water storage system and method provided by this invention have the following beneficial effects: The compressed air pressurized pumped-storage energy storage system and method provided by this invention employs a top-down, layered arrangement of pressure vessels. The top of the pressure vessels is connected via a gas pipeline, and the bottom is connected to a low-level external water source via a water supply pipeline equipped with a water-driven device. By combining real-time monitoring and control of liquid level and pressure, the head pressure formed by the natural elevation difference is coupled with the pressure energy of compressed air. During energy storage, through a top-down sequential water injection, the gas is compressed stage by stage and ultimately stored in the lowest unit, efficiently converting electrical energy into the gravitational potential energy of water and the pressure energy of air. During energy release, through a bottom-up sequential drainage, the expansion energy of the high-pressure gas is superimposed with the head potential energy of each layer of water, jointly driving the turbine to generate electricity stably. This design can achieve large-scale energy storage using underground or artificially constructed chambers, increasing the energy storage density per unit space. Simultaneously, the layered sequential operation logic and the control strategy based on real-time feedback effectively smooth out the total pressure fluctuations at the turbine inlet, ensuring efficient and stable operation of the equipment, improving the overall system efficiency and reliability, and enhancing the system's adaptability to different terrain conditions. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the compressed air booster pumped water storage system provided in an embodiment of the present invention; Figure 2 A schematic diagram of another compressed air booster pumped water storage system provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of a pressure vessel structure provided in an embodiment of the present invention; Figure 4 The electrical connection block diagram of the controller module provided in the embodiment of the present invention.

[0018] Among them, 1-pressure vessel, 21-main water pipe, 22-branch water pipe, 3-external water source, 4-water-driven equipment, 51-main gas pipe, 52-branch gas pipe, 6-controller, 61-signal acquisition unit, 62-analysis and processing unit, 63-control unit, 7-liquid level sensor, 8-pressure detection equipment, 9-first valve, 10-second valve, 101-check valve. Detailed Implementation

[0019] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the invention will be thorough and complete.

[0020] Example 1 See Figures 1-3 This invention provides a compressed air booster pumped water storage system, which mainly includes: a pressure vessel 1, a water-driven device 4, an external water source 3, a liquid level sensor 7, a pressure detection device 8, and a controller 6. The connections and functions of each component are as follows: Pressure vessel 1 is configured as a closed chamber structure, such as a square, circular, or elliptical shape. Pressure vessels 1 are arranged in layers from top to bottom, with the same height difference between any two adjacent layers. See also Figure 3 Each layer contains one or more interconnected pressure vessels 1; when multiple pressure vessels 1 are set, the tops of the pressure vessels 1 set on the same layer are connected by gas pipes, and the bottoms are connected by water pipes.

[0021] For example, pressure vessel 1 is placed in a suitable location and divided into three layers according to height, from top to bottom as the first layer, the second layer, and the third layer. The vertical distance between adjacent layers is 50m. That is, the height of pressure vessel 1 in the first layer is 100-150m, the height of pressure vessel 1 in the second layer is 50-100m, and the height of pressure vessel 1 in the third layer is 0-50m. Multiple pressure vessels 1 distributed in the same layer are connected by water pipelines and gas pipelines to form a single-layer pressure vessel 1 with an effective volume of 10,000m³.

[0022] A liquid level sensor 7 is installed inside the pressure vessel 1 to detect the real-time liquid level inside the pressure vessel 1. A pressure detection device 8 is installed inside the lowest pressure vessel 1 to detect the real-time pressure inside the lowest pressure vessel 1. The liquid level sensor 7 and the pressure detection device 8 are connected to a controller 6, which acquires and processes the real-time signals uploaded by the liquid level sensor 7 and the pressure sensor; in this embodiment, the controller 6 is a PLC.

[0023] The bottom of the inner cavity of pressure vessel 1 is connected to an external water source 3 via a water supply pipe, on which a water-driven device 4 is installed. For example, the external water source 3 is a reservoir with a volume of 50,000 m³, and the water-driven device 4 is a reversible pump-turbine with a rated power of 50 MW. The reversible pump-turbine functions as a pump during the energy storage phase and as a power generator during the energy release phase. The tops of the inner cavities of each layer of pressure vessel 1 are connected via gas pipes, each equipped with a valve to individually control the gas flow of each layer of pressure vessel 1. The upper height of the external water source 3 is less than the lower height of the bottommost pressure vessel 1, providing different gravitational potential energies to each layer of pressure vessel 1.

[0024] See Figure 1 and Figure 2 The water supply pipeline can adopt the following specific structure, including: a main water supply pipe 21 and branch water supply pipes 22. An external water source 3 is connected to one end of the main water supply pipe 21, and the other end of the main water supply pipe 21 is connected to the bottom of the inner cavity of the pressure vessel 1 via the branch water supply pipes 22; a first valve 9 is installed on the branch water supply pipes 22. To further improve the suppression of head fluctuations during the energy release phase, a pressure buffer tank can also be connected to the main water supply pipe 21.

[0025] See further Figure 1 and Figure 2 The gas pipeline can adopt the following specific structure, including: a main gas pipe 51 and gas branch pipes 52. The inner cavity of the pressure vessel 1 is connected to the main gas pipe 51 via the gas branch pipes 52. A second valve 10 for controlling the gas flow is installed on the gas branch pipe 52. See also Figure 2 To further improve the stability of the system, each pressure vessel 1 can be equipped with two gas branch pipes 52; each gas branch pipe 52 is equipped with a one-way valve 101, and the one-way valves 101 on the two gas branch pipes 52 have opposite conduction directions; the two gas branch pipes 52 are used to fill the pressure vessel 1 with gas during the energy storage stage and to discharge the gas in the pressure vessel 1 during the energy release stage, respectively, to prevent gas backflow from causing instability in the energy storage stage or the energy release stage of the system.

[0026] See Figure 1 and Figure 4To further improve the automation level of the compressed air booster pumped storage system, the controller 6 can be configured with the following functional modules, specifically including a signal acquisition unit 61, an analysis and processing unit 62, and a control unit 63, with data interaction between the functional modules. Among them: The signal acquisition unit 61 is used to acquire the real-time liquid level signal of the pressure vessel 1 from the liquid level sensor 7, and to acquire the real-time pressure signal of the lowest pressure vessel 1 from the pressure detection device 8.

[0027] The analysis and processing unit 62 is used to analyze the real-time liquid level value corresponding to the real-time liquid level signal, compare the real-time liquid level value with the preset liquid level high value and liquid level low value, and issue a first control signal when the real-time liquid level value is greater than the liquid level high value and issue a second control signal when the real-time liquid level value is lower than the liquid level low value; and is used to analyze the real-time pressure value corresponding to the real-time pressure signal, and issue a third control signal when the real-time pressure value is greater than the preset pressure threshold.

[0028] The control unit 63 is used to acquire a first control signal and control the water-driven device 4 to shut down and control the corresponding first valve 9 on the current pressure vessel 1 to shut down during the energy storage phase, thereby stopping the injection of water into the current pressure vessel 1; acquire a second control signal and control the corresponding first valve 9 on the current pressure vessel 1 to shut down during the energy release phase, thereby stopping the drainage of water from the current pressure vessel 1; and acquire a third control signal and control the water-driven device 4 to shut down and control the corresponding first valve 9 on the lowest pressure vessel 1 to shut down during the energy storage phase, thereby stopping the injection of water into the lowest pressure vessel 1.

[0029] Example 2 See Figure 1 and Figure 2 This invention provides a compressed air pressurized pumped water storage method, which is based on the compressed air pressurized pumped water storage system described in Embodiment 1. The method includes two stages: energy storage and energy release. The energy storage stage includes the following steps: Step S11. Set the gas in all pressure vessels 1 to normal pressure (i.e., atmospheric pressure).

[0030] Step S12. Turn on the water-driven device 4 and inject water into each layer of pressure vessel 1 in a top-to-bottom order, compressing the gas layer by layer into the bottom layer of pressure vessel 1 in a top-to-bottom order; when the water injection of each layer of pressure vessel 1 is completed, close the water and gas passage on that layer of pressure vessel 1 and start injecting water into the next layer of pressure vessel 1.

[0031] The energy release phase includes the following steps: Step S21. Open the water passage on the lowest pressure vessel 1, discharge the water in the pressure vessel 1 to the external water source 3 through the water pipeline and drive the power generation equipment to generate electricity until the water in the lowest pressure vessel 1 is discharged.

[0032] Step S22. Starting from the pressure vessel 1 set on the second layer from bottom to top, drain the water from each layer of pressure vessel 1 in sequence from bottom to top, and discharge the water in each pressure vessel 1 to the external water source 3 through the water supply pipe to drive the power generation equipment to generate electricity; when draining, open the second valve 10 between the pressure vessel 1 being drained and the lowest layer pressure vessel 1 until the water in all pressure vessels 1 is drained.

[0033] Specifically, during the energy release phase, in the strictly sequential drainage mode—that is, completely emptying one layer before opening the next—the total pressure at the turbine inlet exhibits a step-like decrease. At the end of each drainage stage, the pressure drops to a lower point; when the next layer opens, the pressure jumps to a new starting point. This periodic pressure fluctuation can also lead to increased head fluctuations.

[0034] Based on this, a preferred embodiment optimizes the energy release phase as follows: the drainage period of any pressure vessel 1 at any level partially overlaps with the drainage period of the pressure vessel 1 at the adjacent upper level. For example, assuming the total drainage time of the lowest pressure vessel 1 is 1 hour, while draining pressure vessel 1 at this level for 0.5 hours, the pressure vessel 1 at the next lower level is simultaneously opened for drainage. Thus, the drainage periods of the lowest and next lower pressure vessels overlap by 0.5 hours. The overlapping drainage periods between different levels can smooth out the pressure abrupt change curve caused by the switching between levels. By optimizing the pressure threshold at the start of the overlap and the flow ratio during the overlap period, the fluctuation range of the total pressure at the turbine inlet can be controlled within a small range, achieving precise control of the head. A stable head is directly converted into a stable driving torque on the turbine runner, reducing the fluctuation of the generator's output power and improving power quality, thus meeting the grid connection requirements. Furthermore, strict sequential switching may cause water hammer pressure in the pipeline due to the rapid opening and closing of valves and sudden changes in the flow channel, impacting the pipeline and equipment. Overlapping drainage periods allow valves to open and close more gently, reducing abrupt changes in water flow patterns, lowering the risk of hydraulic shock, and improving system safety.

[0035] Example 3 In a preferred embodiment of the present invention, to achieve more precise control, a mathematical model can be established to calculate the parameters of the system operating conditions at any given time. The compressed air booster pumped storage system provided in this embodiment of the present invention comprises three interconnected subsystems: a pressure vessel, a water pipeline, and a water-driven device. The physical parameters of the overall technical solution require solving the control equations of each subsystem simultaneously. The overall coupled mathematical model is now established, as shown in Table 1:

[0036] Table 1 The above nine governing equations together constitute the mathematical function model of this invention. Given the initial state parameters and boundary conditions, the parameters of the system operating conditions at any time can be obtained based on ordinary differential equation solving algorithms such as the Runge-Kutta method.

[0037] The detailed calculation steps for the system operating conditions at any given time are as follows: Step S31. Input system parameters , , , , , , , and .

[0038] Step S32. Determine based on system constants and boundary condition parameters and dimensionless parameters , and .

[0039] Step S33. Calculate the initial physical condition parameters based on the above parameters. , , , , , , , and .

[0040] Step S34. Determine the time step and the numerical solution method for the system of ordinary differential equations.

[0041] Step S35. Calculate the physical operating parameters at the next moment. , , , , , , , and Check the convergence of the internal iteration; if it does not converge, return to step S34.

[0042] Step S36. Calculate the target result and end the calculation.

[0043] See Figure 1 and Figure 2 The compressed air booster pumped water storage system and method provided in this embodiment of the invention have the following beneficial effects: The compressed air pressurized pumped-storage energy storage system and method provided in this invention employs a top-down layered arrangement of pressure vessels 1, with the top of the pressure vessels 1 connected via a gas pipeline and the bottom connected to a low-level external water source 3 via a water supply pipeline equipped with a water-driven device 4. By combining real-time monitoring and control of liquid level and pressure, the head pressure formed by the natural elevation difference is coupled with the pressure energy of compressed air. During energy storage, through sequential water injection from top to bottom, the gas is compressed stage by stage and finally stored in the lowest unit, efficiently converting electrical energy into the gravitational potential energy of water and the pressure energy of air. During energy release, through sequential drainage from bottom to top, the expansion energy of the high-pressure gas is superimposed with the head potential energy of each layer of water, jointly driving the turbine to generate electricity stably. This design can achieve large-scale energy storage using underground or artificially constructed chambers, increasing the energy storage density per unit space. Meanwhile, the hierarchical sequential operation logic and the control strategy based on real-time feedback can effectively smooth out the total pressure fluctuations at the turbine inlet, ensuring that the equipment operates under efficient and stable conditions, improving the overall efficiency and reliability of the system, and enhancing the system's adaptability to different terrain conditions.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A compressed air pressurized pumped water storage system, characterized in that, include: Pressure vessels, water-driven equipment, water pipelines, external water sources, level sensors, pressure detection equipment and controllers; The pressure vessel is designed as a closed chamber structure, and the pressure vessels are arranged in layers from top to bottom; A liquid level sensor is installed inside the pressure vessel, and a pressure detection device is installed in the lowest layer of the pressure vessel. The liquid level sensor and the pressure detection device are connected to the controller signal. The bottom of the pressure vessel's inner cavity is connected to an external water source via a water supply pipe, and a water-driven device is installed on the water supply pipe. The top of the inner cavity of all pressure vessels is connected by gas pipelines, and each pipeline is equipped with a valve that controls the gas flow of each pressure vessel. The height of the upper part of the external water source is less than the height of the lower part of the lowest pressure vessel.

2. The compressed air booster pumped water storage system according to claim 1, characterized in that, The water supply pipeline includes: a main water supply pipe and branch water supply pipes; An external water source is connected to one end of the main water supply pipe, and the other end of the main water supply pipe is connected to the bottom of the pressure vessel cavity through branch water supply pipes. A first valve is installed on the branch water supply pipe.

3. The compressed air booster pumped water storage system according to claim 2, characterized in that, A pressure buffer tank is connected to the main water supply pipe.

4. The compressed air booster pumped water storage system according to claim 2, characterized in that, The gas pipeline includes: a main gas pipe and gas branch pipes; The inner cavity of the pressure vessel is connected to the main gas pipe via gas branch pipes; A second valve is installed on the gas branch pipe.

5. The compressed air booster pumped water storage system according to claim 4, characterized in that, Each pressure vessel on each floor is equipped with two gas branches; each gas branch is equipped with a one-way valve, and the one-way valves on the two gas branches are in opposite directions.

6. The compressed air booster pumped water storage system according to claim 1, characterized in that, The water-driven device is a reversible water pump turbine.

7. The compressed air booster pumped water storage system according to claim 1, characterized in that, The controller includes: The signal acquisition unit is used to acquire the real-time liquid level signal of the pressure vessel from the liquid level sensor, and to acquire the real-time pressure signal of the lowest pressure vessel from the pressure detection device. The analysis and processing unit is used to analyze the real-time liquid level value corresponding to the real-time liquid level signal, compare the real-time liquid level value with the preset liquid level high value and liquid level low value, and issue a first control signal when the real-time liquid level value is greater than the liquid level high value and issue a second control signal when the real-time liquid level value is lower than the liquid level low value; and to analyze the real-time pressure value corresponding to the real-time pressure signal, and issue a third control signal when the real-time pressure value is greater than the preset pressure threshold. The control unit is configured to acquire a first control signal and control the water-driven equipment to shut down and control the corresponding first valve on the current pressure vessel to shut down during the energy storage phase, thereby stopping the injection of water into the current pressure vessel; acquire a second control signal and control the corresponding first valve on the current pressure vessel to shut down during the energy release phase, thereby stopping the drainage of water from the current pressure vessel; and acquire a third control signal and control the water-driven equipment to shut down and control the corresponding first valve on the lowest pressure vessel to shut down during the energy storage phase, thereby stopping the injection of water into the lowest pressure vessel.

8. The compressed air booster pumped water storage system according to claim 1, characterized in that, The height difference between any two adjacent pressure vessels is the same.

9. A method for compressed air pressurization pumped-storage water storage, the method being implemented based on the compressed air pressurization pumped-storage water storage system according to any one of claims 1-5; characterized in that, This method comprises two stages: energy storage and energy release; the energy storage stage includes the following steps: Step S11. Set the gas in all pressure vessels to atmospheric pressure; Step S12. Turn on the water-driven equipment and inject water into the pressure vessels of each layer in order from top to bottom, compressing the gas layer by layer into the pressure vessel of the bottom layer in order from top to bottom; when the water injection of each layer of pressure vessel is completed, close the water and gas passage on that layer of pressure vessel. The energy release phase includes the following steps: Step S21. Open the water passage on the lowest pressure vessel, discharge the water in the pressure vessel to an external water source through the water pipeline and drive the power generation equipment to generate electricity until the water in the lowest pressure vessel is completely discharged. Step S22. Starting with the pressure vessel set on the second layer from bottom to top, drain the pressure vessels of each layer in order from bottom to top, and discharge the water in the pressure vessels one by one to the external water source through the water supply pipe to drive the power generation equipment to generate electricity; when draining, open the gas pipe between the pressure vessel being drained and the lowest pressure vessel until the water in all pressure vessels has been drained.

10. The compressed air pressurization pumped water storage method according to claim 9, characterized in that, During the energy release phase, the drainage period of the pressure vessel on any layer partially overlaps with the drainage period of the pressure vessel on the adjacent upper layer.

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