Volumetric supercritical carbon dioxide Brayton cycle variable load system

Abstract

The invention provides a volumetric supercritical carbon dioxide Brayton cycle variable load system, belongs to the technical field of supercritical carbon dioxide Brayton cycle power generation, and can at least partially solve the problems that an existing steam Rankine cycle unit does not utilize the supercritical carbon dioxide Brayton cycle to integrally operate on a supercritical point and has no project. The Brayton cycle system comprises a compressor, a main loop and an adjusting branch, the adjusting branch comprises a pressure adjusting assembly, the amount of circulating carbon dioxide working media in the system is adjusted, the inlet pressure of the compressor is adjusted, and the working point of the compressor is changed; the temperature and pressure of the carbon dioxide working medium at the turbine inlet are changed by adjusting the heat exchange amount of the heat source heat exchanger, and rapid load changing is achieved.

Description

Technical Field

[0001] This invention belongs to the field of supercritical carbon dioxide Brayton cycle power generation technology, specifically relating to a volumetric supercritical carbon dioxide Brayton cycle variable load system. Background Technology

[0002] Due to the inherent characteristics of new energy power, namely intermittent supply and large fluctuations, the absorption of new energy power places higher demands on coal-fired power generating units, requiring them to have better flexibility. However, due to limitations such as working fluid phase change, heat transfer and equipment, the peak-shaving rate of traditional coal-fired power generating units can only reach 2.5%-4%Pe / min, which cannot meet the peak-shaving demand.

[0003] In supercritical carbon dioxide power generation systems, the temperature and pressure parameters of the circulating carbon dioxide working fluid are all above the supercritical point. The entire cycle process does not involve phase change, and the flexibility of load variation is superior to that of traditional steam Rankine cycle units. Existing load variation methods for steam Rankine cycle units, including constant pressure or sliding pressure load variation methods, are used for supercritical carbon dioxide Brayton cycles. However, these methods do not take advantage of the fact that the supercritical carbon dioxide Brayton cycle operates entirely at the supercritical point and has no specific phase change, thus failing to fully utilize the flexibility advantages of the Brayton cycle itself. Therefore, this invention proposes a volumetric supercritical carbon dioxide Brayton cycle load variation system. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art, and to provide a volumetric supercritical carbon dioxide Brayton cycle variable load system.

[0005] One aspect of the present invention provides a volumetric supercritical carbon dioxide Brayton cycle variable load system, the system comprising: The main circuit includes a regenerator, a heater, a power unit, and a compressor with an inlet, a regulating outlet, and a main outlet. The main outlet channel of the compressor is connected to the cold-side inlet of the regenerator, the cold-side outlet channel of the regenerator is connected to the heater, the heater channel is connected to the inlet of the power unit, the outlet channel of the power unit is connected to the hot-side inlet of the regenerator, and the hot-side outlet channel of the regenerator is connected to the inlet of the compressor. The regulating branch includes: A pressure regulating assembly, the inlet channel of which is connected to the regulating outlet of the compressor for depressurizing the supercritical carbon dioxide working fluid flowing out of the regulating outlet of the compressor. The outlet channel of the pressure regulating component is connected to the main circuit pipeline section between the cold side inlet of the regenerator and the heater.

[0006] Furthermore, the system also includes a precooler, the precooler channel being connected to the heat measurement inlet of the regenerator and the inlet of the compressor to cool the carbon dioxide working fluid in the main circuit.

[0007] Furthermore, the system also includes a pressure stabilizing tank disposed in the main circuit, the pressure stabilizing tank being connected to the outlet of the precooler to receive and stabilize the carbon dioxide working fluid in the main circuit.

[0008] Specifically, the compressor is connected to the electric motor via a coupling.

[0009] Specifically, the pressure regulating assembly includes a high-pressure tank disposed in the bypass regulating branch for storing carbon dioxide as a working fluid.

[0010] Preferably, the pressure regulating assembly further includes a high-pressure regulating valve disposed in the bypass regulating branch for controlling the flow rate of carbon dioxide working fluid, the high-pressure regulating valve channel being connected to the regulating outlet of the compressor and the high-pressure tank.

[0011] Specifically, the pressure regulating assembly also includes a pressure reducing valve disposed in the bypass regulating branch for stabilizing the pressure in the downstream pipeline of the high-pressure tank.

[0012] Furthermore, the power-generating component includes a turbine, and the turbine channel is connected to the heat measurement inlet of the heater and the regenerator.

[0013] Furthermore, the power-generating component also includes a generator, and the output shaft of the turbine is connected to the generator rotor via a coupling.

[0014] In this embodiment, the heater is a heat source heat exchanger.

[0015] The beneficial effects of this invention are as follows: During operation, by introducing and discharging the circulating carbon dioxide working fluid into and out of the high-pressure tank, the amount of circulating carbon dioxide working fluid in the system is adjusted, the compressor inlet pressure is adjusted, the compressor operating point is changed, and the heat exchange capacity of the heat source heat exchanger is adjusted, thereby changing the temperature and pressure of the carbon dioxide working fluid at the turbine inlet and achieving rapid load change. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the system connection of a volumetric supercritical carbon dioxide Brayton cycle variable load system according to the present invention. Figure 2 This is a compressor performance curve diagram of a positive displacement supercritical carbon dioxide Brayton cycle variable load system according to the present invention; Among them, 1 is the electric motor, 2 is the compressor, 3 is the regenerator, 4 is the heat source heat exchanger, 5 is the turbine, 6 is the generator, 7 is the precooler, 8 is the pressure stabilizing tank, 9 is the high pressure regulating valve, 10 is the high pressure tank, and 11 is the pressure reducing valve. exist Figure 2 In the figure, the left side shows the performance curve when the compressor inlet pressure is P1, and the right side shows the performance curve when the compressor inlet pressure is P2. P1 is greater than P2. Points A and B are the operating points. Detailed Implementation

[0017] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] like Figure 1 As shown, a specific embodiment of the present invention provides a volumetric supercritical carbon dioxide Brayton cycle variable load system, the system comprising: The main circuit is equipped with a compressor 2, a regenerator 3, a heater, and a working assembly, which are equipped with an inlet, a regulating outlet, and a main outlet. The main outlet pipe of the compressor 2 is connected to the cold side inlet of the regenerator 3. The cold side outlet of the regenerator 3 is connected to the heater through a conveying channel. The heater is connected to the inlet of the working assembly through a working fluid conveying channel. The outlet of the working assembly is connected to the hot side inlet of the regenerator 3 through a conveying channel. The hot side outlet of the regenerator 3 is connected to the inlet of the compressor 2 through a conveying channel. A pressure regulating assembly, the inlet channel of which is connected to the regulating outlet of compressor 2, for depressurizing the supercritical carbon dioxide working fluid flowing out of the regulating outlet of compressor 2. The outlet channel of the pressure regulating component is connected to the main circuit pipeline section between the cold side inlet of the regenerator 3 and the heater; The main loop path constitutes a complete supercritical carbon dioxide Brayton cycle with regenerative heating. By controlling the flow rate of the working fluid flowing through the regulating branch, the flow rate of the working fluid entering the working components and the system pressure level are adjusted to achieve system load regulation.

[0019] In this embodiment, the system also includes a precooler 7, the channel of which is connected to the heat measurement inlet of the regenerator 3 and the inlet of the compressor 2 to cool the carbon dioxide working fluid in the main circuit.

[0020] In this embodiment, a precooler 7 is provided to cool the working fluid to the state required at the inlet of compressor 2: After the working fluid performs work by flowing through the working components, it flows out from the hot side outlet of the regenerator 3. Although it has been initially cooled by the regenerator 3 (the heat is transferred to the high-pressure working fluid on the cold side), its temperature is usually still significantly higher than the ideal state required by the inlet of the compressor 2.

[0021] The working fluid at the compressor inlet 2 needs to be in a high-density state (close to or slightly above the critical point, in a liquid or dense supercritical state). This is a key prerequisite for the efficient and stable operation of a positive displacement compressor. A high-density working fluid means that more mass is contained within a unit volume, resulting in higher compression efficiency and lower power consumption.

[0022] The core function of the precooler 7 is to further cool the working fluid flowing out from the hot side outlet of the regenerator 3, reducing its temperature to the low temperature required for the compressor 2 inlet design (usually close to or slightly higher than the critical temperature of 31.1°C), thereby significantly increasing the density of the working fluid and bringing it to a state suitable for the compressor 2 to inhale and process.

[0023] Furthermore, the function of the precooler 7 is as follows: Ensure system stability and efficiency: Maintaining compressor 2 efficiency: As mentioned earlier, cooling the working fluid to a high-density state is fundamental to ensuring the efficient and reliable operation of the positive displacement compressor. Overheated working fluid entering compressor 2 will cause a sharp drop in efficiency, a surge in power consumption, and may even trigger unstable phenomena such as surge.

[0024] Controlling the compressor inlet temperature: The precooler 7 is the primary means of controlling the compressor inlet temperature. A stable inlet temperature is crucial for system control.

[0025] Impact on Cycle Efficiency: Although the precooling process itself dissipates heat to the environment (cooling water or air), representing an energy loss, it is a necessary price to pay for achieving high-efficiency compression. Without efficient cooling, the losses in the compression process would be greater, and the overall cycle efficiency would actually decrease. Optimizing the performance of the precooler 7 (such as reducing the cold-end temperature difference) also contributes to improving the system's net efficiency.

[0026] Special significance in variable load systems: When a large amount of bypass working fluid (usually unheated, low-temperature high-pressure working fluid, after being depressurized by the pressure regulating component) is injected into the precooler inlet: This will significantly reduce the average temperature of the working fluid at the inlet of the precooler 7.

[0027] This reduces the heat load on the precooler 7 (the amount of heat that needs to be removed is reduced).

[0028] At the same time, it also directly affects the state (temperature and flow rate) of the mixed working fluid entering the compressor 2 inlet.

[0029] Based on the above-mentioned basic technical solution of the present invention, the system also includes a pressure stabilizing tank 8 installed in the main circuit. The pressure stabilizing tank 8 is connected to the outlet of the precooler 7 to receive and stabilize the carbon dioxide working fluid in the main circuit.

[0030] In this embodiment, the function of the pressure stabilizing tank 8 is as follows: Suppressing flow and pressure pulsations (core function) As a large-volume air chamber connected in the pipeline, it can: Peak flow / pressure absorption: When the output flow of compressor 2 increases instantaneously, some of the working fluid flows into the tank for storage to prevent a sudden increase in downstream pressure.

[0031] Replenishing trough flow / pressure: When the output flow rate decreases instantaneously, the working fluid stored in the tank is released to replenish it, preventing a sudden drop in downstream pressure.

[0032] Smoothing fluid: By using the compressibility of the gas to buffer pulsations, a near-continuous and stable flow is obtained downstream.

[0033] Maintain system pressure stability Physical property sensitivity of supercritical CO2: Near the critical point (31.1°C, 7.38 MPa), the physical properties of CO2, such as density and specific heat capacity, are extremely sensitive to minute changes in temperature and pressure. Pressure fluctuations can cause drastic changes in the working fluid's state.

[0034] The function of pressure stabilizing tank 8: Provides system pressure inertia: Large-capacity tanks can reduce short-term pressure fluctuations caused by load changes, valve adjustments, or branch switching.

[0035] Stable critical state: Ensure that the working fluid in key locations such as the compressor inlet and heat exchanger area is always maintained in the required supercritical state, and avoid accidental crossing of the critical point, which could lead to sudden changes in physical properties and control instability.

[0036] Improve the smoothness of variable load regulation response. Variable load challenge: When the bypass valve opening is changed rapidly, the flow and pressure in the main circuit may step or oscillate.

[0037] The function of pressure stabilizing tank 8: Shock absorption and regulation: The tank volume can buffer the instantaneous impact of sudden changes in bypass flow on the main circuit, making the system pressure change more gradual.

[0038] Provides regulation capacity: Provides an additional "buffer pool" for the control system, allowing for a certain degree of delay tolerance between flow regulation commands and actual operating condition changes.

[0039] Changes in the total amount of working fluid (thermal expansion and contraction) Fluctuations in the total amount of working fluid in the system: During start-up, shutdown, or load changes, changes in the system's average temperature can lead to significant changes in the total volume of supercritical CO2 (thermal expansion / cold contraction).

[0040] The function of pressure stabilizing tank 8: As a regulating container for the total amount of working fluid in the system, it accommodates volume fluctuations through changes in liquid level (if it is a two-phase system) or pressure, avoiding overpressure caused by thermal expansion or low-pressure alarm shutdown caused by cold contraction.

[0041] In this embodiment, the compressor 2 is connected to the motor 1 via a coupling, and the heater is a heat source heat exchanger 4.

[0042] In this embodiment, the heat source heat exchanger 4 includes: High-temperature section: Corrugated inner wall / threaded outer composite pipe (pressure resistance ≥25MPa); Low temperature section: micro-finned heat exchange tubes (fin height 0.2-0.5mm); A variable cross-section transition cavity is set between the high and low temperature sections.

[0043] When the heat source side medium is molten salt, the inner wall of the primary side flow channel is coated with a borosilicate glass layer (thickness 50-100μm), and the molten salt inlet temperature is ≥550℃.

[0044] Heat exchanger 4 also includes a dynamic heat source flow regulation system: a temperature sensor monitors the CO2 outlet temperature; a PID controller generates valve opening commands; an electric regulating valve controls the flow rate of the heat source medium; and the response time to load changes is ≤30 seconds.

[0045] Furthermore, the pressure regulating assembly includes a high-pressure tank 10 disposed in the bypass regulating branch for storing carbon dioxide as the working fluid.

[0046] In this embodiment, the high-pressure tank 10 acts as an absorber of variable load shocks to ensure stable operation of the compressor. At the same time, the high-pressure tank 10 can also act as a filter for high-frequency pulsation to extend the life of the regulating valve. Furthermore, the high-pressure tank 10 can serve as the last barrier for system safety to prevent overpressure cascading accidents.

[0047] In a preferred embodiment, the pressure regulating assembly also includes a high-pressure regulating valve 9 disposed in the bypass regulating branch for controlling the flow rate of carbon dioxide working fluid. The high-pressure regulating valve 9 is connected to the regulating outlet of the compressor 2 and the high-pressure tank 10 through the working fluid delivery channel.

[0048] Specifically, the working fluid drawn from the regulating outlet of compressor 2 is at the highest pressure of the system (close to the outlet pressure of compressor 2). If it is directly injected into the low-pressure circuit (such as the inlet of precooler 7 or the cooling pipeline of regenerator 3), it will cause severe turbulence, noise and energy loss due to excessive pressure difference.

[0049] Execution of high-pressure regulating valve 9: By forcing the working fluid through a narrow valve orifice using the principle of throttling expansion, pressure energy is converted into heat / kinetic energy, which significantly reduces the working fluid pressure and stabilizes the outlet pressure at the target low pressure value (such as the low pressure side pressure of the main circuit).

[0050] Typical pressure drop: from 15-20MPa to 7-10MPa (depending on system design).

[0051] Meanwhile, the high-pressure regulating valve can achieve precise flow control: The implementation logic for variable load: System load regulation depends on controlling the working fluid flow rate in the bypass branch: Increasing the flow rate → More high-pressure working fluid is bypassed → The main flow rate into the heater / turbine decreases → The system output power decreases.

[0052] Reduced flow rate → More working fluid flows through the main circuit → Increased turbine work → Increased system output power.

[0053] The core function of high-pressure regulating valve 9: The regulating valve opening is used to precisely control the mass flow rate of the bypass working fluid.

[0054] Fast response control commands are used to achieve second-level load regulation (such as responding to grid frequency regulation requirements).

[0055] In another specific embodiment, the pressure regulating assembly further includes a pressure reducing valve 11 disposed in the bypass regulating branch for stabilizing the pressure in the downstream pipeline of the high-pressure tank 10.

[0056] In this embodiment, the function of the pressure reducing valve 11 is as follows: Safety barrier function (core): Scenario: When high-pressure regulating valve 9 is malfunctioning and fully open Risk: Uncontrolled high-pressure working fluid directly impacts low-pressure pipelines.

[0057] Pressure reducing valve backstop: Forces downstream pressure to be limited to a safe set value (e.g., 10MPa) to prevent overpressure and rupture of equipment such as regenerators / precoolers.

[0058] Maintaining stability on the low-pressure side: Problem: Adjusting outlet pressure changes by varying compressor speed during load changes. Pressure reducing valve 11 response: Automatically compensates for upstream pressure fluctuations to output a constant low pressure, ensuring stable pressure at the bypass injection point (whether connected to precooler 7 or regenerator 3).

[0059] Energy saving and noise reduction: In contrast, the energy is completely lost in turbulence due to manual adjustment of the opening of the throttle valve.

[0060] Pressure reducing valve reduces pressure: Pressure energy is converted into kinetic energy in an orderly manner through multi-stage expansion chambers. Typical energy consumption reduction: 15-20% (actual measurement under supercritical CO2 conditions).

[0061] Based on the above-mentioned basic technical solution of the present invention, the working component includes a turbine 5, which is connected to the heater and the heat measurement inlet of the regenerator 3 through a working fluid transport channel.

[0062] Specifically, the power-generating components also include generator 1, and the output shaft of turbine 5 is connected to the rotor of generator 1 via a coupling to drive generator 1 to work.

[0063] In this embodiment, turbine 5 can be directly connected in series with the rotor of generator 1 via a rigid coupling and installed as a whole on the same bearing support system (dynamic balance calibration is required), or the output end of turbine 5 can be connected to the input shaft of gearbox via a flexible coupling, and the output shaft of gearbox can drive the rotor of generator 1 through a second coupling to achieve speed matching between turbine 5 and generator 1.

[0064] Furthermore, the present invention also provides a variable load method for a volumetric supercritical carbon dioxide Brayton cycle. The method is implemented using a volumetric supercritical carbon dioxide Brayton cycle variable load system, and the process is as follows: carbon dioxide gas in the pressure tank 8 is pressurized by the compressor 2 and enters the cold side of the regenerator 3 to absorb heat. After absorbing heat, the carbon dioxide enters the heat source heat exchanger 4 to absorb heat further. After further absorbing heat, the carbon dioxide enters the turbine 5 to do work. After doing work, the carbon dioxide enters the hot side of the regenerator 3 to recover waste heat, and then enters the precooler 7 for cooling. The cooled carbon dioxide enters the pressure tank 8 to form a cycle.

[0065] Turbine 5 drives generator 6 to rotate and generate electricity through a coupling, while motor 1 drives compressor 2 to rotate and compress carbon dioxide through a coupling.

[0066] During normal operation, the high-pressure regulating valve 9, high-pressure tank 10, and pressure reducing valve 11 are not in operation. When rapid load change is required, the high-pressure regulating valve 9, high-pressure tank 10, and pressure reducing valve 11 are connected to the system and participate in rapid load change regulation.

[0067] The volume of the high-pressure tank is approximately 20% of the volume of the working fluid circulation system.

[0068] When it is necessary to reduce the unit load, keep the pressure reducing valve 11 closed and open the high-pressure regulating valve 9. A portion of the 20MPa high-pressure carbon dioxide at the compressor 2 outlet enters the high-pressure tank 10 through the high-pressure regulating valve 9 and no longer participates in the circulation. The carbon dioxide present in the circulation system decreases, the pressure at various points in the system decreases, the pressure at the compressor 2 inlet decreases from 9MPa to 8MPa, the pressure ratio of compressor 2 decreases, and the operating point of compressor 2 shifts, such as... Figure 2 As shown, the operating point moves from point A to point B, simultaneously reducing the heat absorption of heat source heat exchanger 4, decreasing the temperature and pressure of carbon dioxide at the inlet of turbine 5, reducing the work done by turbine 5, reducing the power generation of generator 6, and reducing the unit load.

[0069] When the unit load decreases and needs to be increased again, the high-pressure regulating valve 9 is closed and the pressure reducing valve 11 is opened. High-pressure carbon dioxide from the high-pressure tank 10 enters the circulation system, increasing the pressure throughout the system. The pressure at the inlet of compressor 2 rises back to 9 MPa, increasing the pressure ratio of compressor 2 and shifting its operating point. Figure 2 As shown, the working point moves from point B back to point A, simultaneously increasing the heat absorption of the heat source heat exchanger 4, raising the temperature and pressure of carbon dioxide at the inlet of turbine 5, increasing the work done by turbine 5, increasing the power generation of generator 6, and increasing the unit load.

[0070] Based on the above technical solution of the present invention, the system load can be quickly adjusted from 100% to 70% without changing the speed of compressor 2.

[0071] As a fully disclosed specific embodiment, a volumetric supercritical carbon dioxide Brayton cycle variable load system is disclosed, the system comprising: The main circuit is equipped with a compressor 2, a regenerator 3, a heater, and a working assembly, which are equipped with an inlet, a regulating outlet, and a main outlet. The main outlet pipe of the compressor 2 is connected to the cold side inlet of the regenerator 3. The cold side outlet of the regenerator 3 is connected to the heater through a conveying channel. The heater is connected to the inlet of the working assembly through a working fluid conveying channel. The outlet of the working assembly is connected to the hot side inlet of the regenerator 3 through a conveying channel. The hot side outlet of the regenerator 3 is connected to the inlet of the compressor 2 through a conveying channel. A pressure regulating assembly, the inlet channel of which is connected to the regulating outlet of compressor 2, for depressurizing the supercritical carbon dioxide working fluid flowing out of the regulating outlet of compressor 2. The outlet channel of the pressure regulating component is connected to the main circuit pipeline section between the cold-side inlet of the regenerator 3 and the heater. The system also includes a precooler 7, whose channel is connected to the hot-side inlet of the regenerator 3 and the inlet of the compressor 2 to cool the carbon dioxide working fluid in the main circuit. The system also includes a pressure stabilizing tank 8 installed in the main circuit, which is connected to the outlet of the precooler 7 to receive and stabilize the carbon dioxide working fluid in the main circuit. The compressor 2 is connected to the motor 1 via a coupling. The heater is a heat source heat exchanger 4. The pressure regulating component includes a bypass regulating branch for storing carbon dioxide. The high-pressure tank 10 for carbon working fluid, the pressure regulating assembly also includes a high-pressure regulating valve 9 disposed in the bypass regulating branch for controlling the flow rate of carbon dioxide working fluid, the high-pressure regulating valve 9 is connected to the regulating outlet of compressor 2 and high-pressure tank 10 through the working fluid conveying channel, the pressure regulating assembly also includes a pressure reducing valve 11 disposed in the bypass regulating branch for stabilizing the pressure of the downstream pipeline of high-pressure tank 10, the power assembly includes a turbine 5, the turbine 5 is connected to the heater and the heat measurement inlet of regenerator 3 through the working fluid conveying channel, the power assembly also includes a generator 1, the output shaft of turbine 5 is connected to the rotor of generator 1 through a coupling.

[0072] This embodiment also includes a variable load method for a volumetric supercritical carbon dioxide Brayton cycle system. The method is implemented using a volumetric supercritical carbon dioxide Brayton cycle variable load system, and the process is as follows: The carbon dioxide gas in the pressure tank 8 is pressurized by the compressor 2 and then enters the cold side of the regenerator 3 to absorb heat. After absorbing heat, the carbon dioxide enters the heat source heat exchanger 4 to absorb heat further. After further absorbing heat, the carbon dioxide enters the turbine 5 to do work. After doing work, the carbon dioxide enters the hot side of the regenerator 3 to recover waste heat, and then enters the precooler 7 for cooling. After cooling, the carbon dioxide enters the pressure tank 8 to form a cycle.

[0073] Turbine 5 drives generator 6 to rotate and generate electricity through a coupling, while motor 1 drives compressor 2 to rotate and compress carbon dioxide through a coupling.

[0074] During normal operation, the high-pressure regulating valve 9, high-pressure tank 10, and pressure reducing valve 11 are not in operation. When rapid load change is required, the high-pressure regulating valve 9, high-pressure tank 10, and pressure reducing valve 11 are connected to the system and participate in rapid load change regulation.

[0075] The volume of the high-pressure tank is approximately 20% of the volume of the working fluid circulation system.

[0076] When it is necessary to reduce the unit load, keep the pressure reducing valve 11 closed and open the high-pressure regulating valve 9. A portion of the 20MPa high-pressure carbon dioxide at the compressor 2 outlet enters the high-pressure tank 10 through the high-pressure regulating valve 9 and no longer participates in the circulation. The carbon dioxide present in the circulation system decreases, the pressure at various points in the system decreases, the pressure at the compressor 2 inlet decreases from 9MPa to 8MPa, the pressure ratio of compressor 2 decreases, and the operating point of compressor 2 shifts, such as... Figure 2 As shown, the operating point moves from point A to point B, simultaneously reducing the heat absorption of heat source heat exchanger 4, decreasing the temperature and pressure of carbon dioxide at the inlet of turbine 5, reducing the work done by turbine 5, reducing the power generation of generator 6, and reducing the unit load.

[0077] When the unit load decreases and needs to be increased again, the high-pressure regulating valve 9 is closed and the pressure reducing valve 11 is opened. High-pressure carbon dioxide from the high-pressure tank 10 enters the circulation system, increasing the pressure throughout the system. The pressure at the inlet of compressor 2 rises back to 9 MPa, increasing the pressure ratio of compressor 2 and shifting its operating point. Figure 2 As shown, the working point moves from point B back to point A, simultaneously increasing the heat absorption of the heat source heat exchanger 4, raising the temperature and pressure of carbon dioxide at the inlet of turbine 5, increasing the work done by turbine 5, increasing the power generation of generator 6, and increasing the unit load.

[0078] Based on the above-described technical solution of the present invention, the ratio of the volume of the high-pressure tank 10 to the volume of the circulation system can still be modified and improved.

[0079] In summary, the embodiments disclosed herein have at least the following technical effects: Achieve rapid, wide-range load regulation: Its core advantage lies in achieving rapid load changes through the bypass regulating branch (high pressure tank 10 + high pressure regulating valve 9 + pressure reducing valve 11).

[0080] Load reduction: Open high-pressure regulating valve 9 to store a portion of the high-pressure working fluid (~20MPa) into high-pressure tank 10, directly reducing the total amount of circulating working fluid. This results in: The pressure drops at various points in the system (e.g., the compressor inlet pressure drops from 9 MPa to 8 MPa).

[0081] The compressor pressure ratio decreases, and the operating point shifts (A→B).

[0082] The pressure and temperature of the working fluid at the turbine inlet decrease (the heat absorption of the heat source heat exchanger needs to be reduced simultaneously).

[0083] As turbine work decreases, generator output power drops.

[0084] Increased load: Close the high-pressure regulating valve and open the pressure reducing valve to release the high-pressure working fluid stored in the high-pressure tank back into the main circuit. This results in: The pressure in various parts of the system has rebounded (e.g., the compressor inlet pressure has risen from 8 MPa back to 9 MPa).

[0085] As the compressor pressure ratio increases, the operating point shifts back to the high-efficiency point (B→A).

[0086] The pressure and temperature of the working fluid at the turbine inlet increase (the heat absorption of the heat source heat exchanger needs to be increased simultaneously).

[0087] As the turbine's work increases, the generator's output power rises.

[0088] Effect: Achieves rapid adjustment of system load from 100% to 70% (second-level response) without changing the compressor speed. This is crucial for responding to grid frequency regulation and matching the fluctuations in renewable energy.

[0089] Maintain efficient and stable compressor operation: Utilization of positive displacement compressor characteristics: The system design fully considers the dependence of positive displacement compressors on high-density working fluid at the inlet.

[0090] The key function of the precooler is to ensure that the working fluid at the outlet of the regenerator is further cooled to near the critical point (~31.1°C), reaching the high-density state (liquid or dense supercritical state) required at the compressor inlet, which greatly improves compression efficiency, reduces power consumption, and avoids unstable phenomena such as surge.

[0091] The pressure stabilizing tank ensures stable inlet flow: It absorbs flow and pressure fluctuations to provide a stable fluid supply to downstream applications, especially the compressor inlet.

[0092] Buffering the pressure shock at the compressor inlet caused by variable load regulation (especially sudden changes in bypass flow) makes the pressure change smoother.

[0093] It accommodates volume fluctuations in the total amount of working fluid in the system caused by thermal expansion and contraction, and maintains the compressor inlet pressure setpoint.

[0094] Stable critical state: Prevents the working fluid at critical locations such as the compressor inlet from unexpectedly crossing the critical point due to pressure fluctuations, which could lead to sudden changes in physical properties and control instability.

[0095] Improve overall system efficiency: High-efficiency compressor operation: By stabilizing the inlet state through the pressure stabilizing tank and maintaining the system pressure level through bypass regulation, the compressor can still operate near its designed high-efficiency point (such as point A) during load changes.

[0096] Heat recovery utilization: The main circuit is designed with heat recovery to effectively recover the waste heat from turbine exhaust, preheat the working fluid entering the heater, and improve thermal efficiency.

[0097] Energy-saving pressure reducing valve: Compared with ordinary throttle valves, pressure reducing valves adopt a multi-stage expansion chamber design, which can reduce energy loss (turbulence loss) in the supercritical CO2 depressurization process by 15-20%, while reducing noise.

[0098] Enhance system security and reliability: Pressure stabilizing tank for overpressure / underpressure protection: buffers pressure fluctuations to prevent thermal expansion from causing system overpressure or cold contraction from causing low-pressure shutdown.

[0099] Pressure reducing valve safety barrier: When the high-pressure regulating valve is malfunctioning and fully open, the pressure reducing valve forces the downstream pressure to be limited to a safe set value (such as 10MPa) to prevent overpressure damage to low-pressure side equipment (regenerator, precooler, etc.).

[0100] Multiple functions of high-pressure tanks: Absorbing variable load shocks: buffering the instantaneous impact of working fluid storage / release on the main circuit.

[0101] Filtering high-frequency pulsations: extends the lifespan of high-pressure regulating valves and pressure reducing valves.

[0102] System safety barrier: Acts as an additional pressure vessel, providing a safety margin.

[0103] Reliability design of heat source heat exchangers: For high-temperature, high-pressure, and corrosive environments (such as molten salt), composite pipes, inner wall coatings (borosilicate glass), and variable cross-section transition cavities are used to improve equipment durability.

[0104] Optimize control and response: Rapid response on the heat source side: The heat source heat exchanger is equipped with a dynamic flow regulation system based on PID temperature sensors and electric regulating valves, with a change-load response time of ≤30 seconds, and works in coordination with the working fluid side regulation.

[0105] Simplified working fluid regulation: Variable load is mainly achieved by operating the high-pressure regulating valve and the pressure reducing valve to increase or decrease the total amount of working fluid and adjust the pressure level, without the need to frequently change the compressor speed, thus reducing the complexity of the main drive control.

[0106] Pressure regulation components work together: the high-pressure regulating valve is responsible for precise flow control and rapid response, while the pressure reducing valve is responsible for downstream pressure stability and safety backup. Together, they achieve efficient and reliable bypass regulation.

[0107] Adaptable to high-parameter heat sources: The heater (heat source heat exchanger) is designed to withstand high temperatures (molten salt inlet ≥550℃) and high pressures (≥25MPa), and uses specially reinforced heat exchange tubes and corrosion-resistant coatings to ensure efficient and reliable heat transfer under harsh conditions.

[0108] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A volumetric supercritical carbon dioxide Brayton cycle variable load system, characterized in that, The system includes: The main circuit includes a regenerator, a heater, a power unit, and a compressor with an inlet, a regulating outlet, and a main outlet. The main outlet channel of the compressor is connected to the cold-side inlet of the regenerator, the cold-side outlet channel of the regenerator is connected to the heater, the heater channel is connected to the inlet of the power unit, the outlet channel of the power unit is connected to the hot-side inlet of the regenerator, and the hot-side outlet channel of the regenerator is connected to the inlet of the compressor. The regulating branch includes: A pressure regulating assembly, the inlet channel of which is connected to the regulating outlet of the compressor for depressurizing the supercritical carbon dioxide working fluid flowing out of the regulating outlet of the compressor. The outlet channel of the pressure regulating component is connected to the main circuit pipeline section between the cold side inlet of the regenerator and the heater.

2. The volumetric supercritical carbon dioxide Brayton cycle variable load system according to claim 1, characterized in that, The system also includes a precooler, the precooler channel of which is connected to the heat measurement inlet of the regenerator and the inlet of the compressor to cool the carbon dioxide working fluid in the main circuit.

3. The volumetric supercritical carbon dioxide Brayton cycle variable load system according to claim 2, characterized in that, The system also includes a pressure stabilizing tank installed in the main circuit, which is connected to the outlet of the precooler to receive and stabilize the carbon dioxide working fluid in the main circuit.

4. The volumetric supercritical carbon dioxide Brayton cycle variable load system according to claim 1, characterized in that, The compressor is connected to the electric motor via a coupling.

5. The volumetric supercritical carbon dioxide Brayton cycle variable load system according to claim 1, characterized in that, The pressure regulating assembly includes a high-pressure tank disposed in the bypass regulating branch for storing carbon dioxide as a working medium.

6. The volumetric supercritical carbon dioxide Brayton cycle variable load system according to claim 5, characterized in that, The pressure regulating assembly also includes a high-pressure regulating valve disposed in the bypass regulating branch for controlling the flow rate of carbon dioxide working fluid, the high-pressure regulating valve channel being connected to the regulating outlet of the compressor and the high-pressure tank.

7. The volumetric supercritical carbon dioxide Brayton cycle variable load system according to claim 5, characterized in that, The pressure regulating assembly also includes a pressure reducing valve disposed in the bypass regulating branch for stabilizing the pressure in the downstream pipeline of the high-pressure tank.

8. The volumetric supercritical carbon dioxide Brayton cycle variable load system according to any one of claims 1 to 7, characterized in that, The power-generating component includes a turbine, and the turbine channel is connected to the heat measurement inlet of the heater and the regenerator.

9. The volumetric supercritical carbon dioxide Brayton cycle variable load system according to claim 8, characterized in that, The power-generating components also include a generator, and the output shaft of the turbine is connected to the generator rotor via a coupling.

10. The volumetric supercritical carbon dioxide Brayton cycle variable load system according to claim 1, characterized in that, The heater is a heat source heat exchanger.

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